STUDIES OF CERTAIN PHYSICAL PROPERTIES OF THE HALOGEN
FLUORIDES AND THEIR HYDROGEN FLUORIDE SOLUTIONS

By
M orton B . P u n is h

A THESIS

S u b m itte d t o th e S c h o o l o f G ra d u a te S tu d ie s o f M ichigan
S t a t e C o lle g e o f A g r i c u l tu r e and A p p lie d S c ie n c e
i n p a r t i a l f u l f i l l m e n t o f t h e req u irem en t®
f o r th e d e g re e o f
DOCTOR OF PHILOSOPHY
D ep artm en t o f C h e m istry

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ACKNOWLEDGMENT
The a u th o r w ish e s t o e x p re ss h i s s in c e r e
a p p r e c i a t i o n t o P r o f e s s o r M. T . R o g e rs f o r h i s
g u id a n c e an d a s s i s t a n c e th ro u g h o u t th e c o u rs e
o f t h i s w o rk , t o D r . J . L . S p e ir s and D r . H. B .
Thompson f o r t h e i r h e lp i n th e p r e p a r a t i o n o f
m a t e r i a l s and e q u ip m e n t, and t o t h e Atomic
E nergy C om m ission f o r a g r a n t s u b s i d i z i n g t h i s
re se a rc h .

•g-KBjg

**
*

VITA

M orton B . P a n is h
C a n d id a te f o r t h e D egree o f
D o c to r o f P h ilo s o p h y

D is s e r ta tio n *

S tu d ie s o f C e r t a i n P h y s ic a l P r o p e r t i e s o f t h e H alo g en
F l u o r i d e s and T h e ir Hydrogen F l u o r id e S o lu tio n s

O u tlin e o f S tu d ie s *
M ajo r S u b je c t — P h y s ic a l C h e m istry
M inor S u b je c ts — O rg an ic C h e m is try , P h y s ic s
B io g r a p h ic a l Item s*
B o rn , A p r i l 8 , 1929, Hew Y ork, N. Y.
U n d e rg ra d u a te S t u d i e s , B ro o k ly n C o l l e g e , D enver
U n i v e r s i t y , 19U7-50
G rad u a te S t u d i e s , M ic h ig a n S t a t e C o lle g e ,
1950-51*, M . S . 1952

iv

TABLE OF CONTENTS
Page
I .

INTRODUCTION..............................................................................................................

1

II.

HISTORICAL SUMMARY................................................................................................

3

A. The H alo g en F l u o r i d e s ............................... ..........................................
B . H ydrogen F l u o r i d e ..............................................................................

3
6

III.

PREPARATION AND HANDLING OF MATERIALS....................................................

9

IV .

VAPOR PRESSURE STUDIES OF HALOGEN FLUORIDE-HYBROGEN FLUORIDE
SOLUTIONS.............................................................................................................

12

A.
B.
C.
D.

T h e o r e t i c a l A s p e c ts ..................
A p p a ra tu s and M eth o d . . . . . . . . . . .........................
D a ta and C a l c u l a t i o n s ......................................... ............................. ..
D is c u s s io n o f th e R e s u l t s ....................................

12
16
21
21

V . CRYOSCOPIC STUDIES OF THE HALOGEN FLUORIDESAND THEIR
HYDROGEN FLUORIDE SOLUTIONS...................................................................

31

38
38
1*3
L3
U5
L8
£0
£0
51
51
52
68
68
69
71

V I . DENSITIES AND AVERAGE MOLAL VOLUMES OFHALOGEN FLUORIDEHYDROGEN FLUORIDE SOLUTIONS...................................................................

72

.

A. T h e o r e t i c a l A s p e c ts ...............................................................................
C ry o s c o p ic S tu d ie s of P u re M a t e r i a l s .................................
Two-Coraponent L iq u id - S o lid P h ase E q u i l i b r i a .................
B . A p p a ra tu s and M ethod ............................................................................
The F r e e z in g P o in t C e l l ..............................................................
T e m p e ra tu re M easu rem en t...............................................................
T herm ocouple C a l i b r a t i o n an d C o n s t r u c t i o n
..
The I c e - p o i n t R e fe re n c e
............................................
The D e te rm in a tio n o f / \ E .......................................
H a n d lin g P ro c e d u re s and P r e p a r a t io n o f S o l u t i o n s . . .
P r e p a r a t i o n o f S o l u t i o n s .....................................................
H ydrogen F l u o r i d e
..........................................................
H ydrogen F lu o r id e - P o ta s s iu m F lu o r id e S o l u t i o n s . ,
C . D a ta and C a l c u l a t i o n s
.............
D. D is c u s s io n o f th e R e s u l t s .................................................................
The P u re M a t e r i a l s
...............................................................
The P h ase D ia g ra m s..........................................................................
H e a ts o f F u s i o n .
...........................................................

31
31

V

TABLE OF CONTENTS - C ontinued
A#
B.
C.
D.
V II.

Page

T h e o r e t i c a l A s p e c ts
. ...............................................................
A p p a ra tu s and M eth o d ..........................................................................
D a ta and C a l c u l a t i o n s
. ........................................................
D is c u s s io n o f th e R e s u l t s ...............................................................

72
7h
75
78

CONDUCTANCE STUDIES OF THE HALOGENFLUORIDES ANDTHEIR
HYDROGEN FLUORIDE SOLUTIONS.................................................................

80

A. T h e o r e t i c a l A s p e c ts ............................................................................. 80
80
M easu rem en t
. . ...........................
S p e c if ic and E q u iv a le n t C o n d u c ta n c e s ..............................
81
.............
83
Non-Aqueous S o l u t i o n s
B . A p p ara tu s and M ethod ...........................
81*
The C o n d u ctan ce B rid g e
..................
81*
The C o n d u ctance C e l l s ...........................................
86
86
C e l l D e s ig n ..................
C e l l C a l i b r a t i o n ..................................................
89
Sample P r e p a r a t i o n and H a n d lin g P r o c e d u r e s ......................103
C . D a ta and C a l c u l a t i o n s .......................................................................... 105
D. D is c u s s io n o f th e R e s u l t s ................................................................. 123
................. 125
C o n d u ctan c es o f th e H alo g en F l u o r i d e s
C o n d u ctan c es o f th e H alogen F lu o rid e -H y d ro gen
F lu o r id e S o l u t i o n s ..................................
127
V III.

MAGNETIC SUSCEPTIBILITIES OF THE HALOGENFLUORIDES...................... 129
A . T h e o r e t i c a l A sp e c ts . ...........
129
132
B . A p p a ra tu s and M eth o d ......................................
The Gouy M a g n e tic B a la n c e
.............
132
The S u s c e p t i b i l i t y T u b e ...................... ..................................... I 3I4
Sample P r e p a r a t i o n and P r o c e d u r e s .......................
13l*
C. D a ta and C a l c u l a t i o n s ..................................................................
ll*0
D. D is c u s s io n o f th e R e s u l t s
...........................
11*8

IX .

SUMMARY........................................................................................................................150

BIBLIOGRAPHY

152

vi

LIST OP TABLES
TABLE
I.

II.

Page
The c o n d u c ta n c e s and f r e e z i n g p o i n t s o f th e h a lo g e n
f l u o r i d e s and t h e i r s o l u t i o n s w ith o t h e r compounds as
r e p o r t e d i n th e l i t e r a t u r e
........................................................

5

The v a p o r p r e s s u r e s o f brom ine p e n ta f lu o r id e - h y d r o g e n
f l u o r i d e s o l u t i o n s a t 0 , 1 5 , and 25° C .....................................................

22

The v a p o r p r e s s u r e s o f io d in e p e n ta f lu o r id e - h y d r o g e n
f l u o r i d e s o l u t i o n s a t 15° C .................................... ........... ...........................

2k

IV . The v ap o r p r e s s u r e s o f c h l o r id e t r i f l u o r i d e - h y d r o g e n
f l u o r i d e s o l u t i o n s a t 0 ° C ...............................................................................

26

III.

V. C a l i b r a t i o n d a t a f o r th e c o p p e r - c o n s t a n t an th e rm o c o u p le

IUi

V I. C ry o s c o p ic d a t a f o r i o d in e p a n ta f lu o r id e - h y d r o g e n f l u o r i d e
s o l u t i o n s ..................

53

V I I . C ry o s c o p ic d a t a f o r brom ine p e n ta f lu o r id e - h y d r o g e n f l u o r i d e
s o lu tio n s
.............

58

V I H . The f r e e z i n g p o i n t s o f i o d in e p e n t a f l u o r i d e , brom ine p e n ta ­
f l u o r i d e , and h y d ro g en f l u o r i d e .................................................................

62

IX . C ry o s c o p ic d a t a f o r s e v e r a l h y d ro g en f lu o r id e - p o ta s s i u m
f l u o r i d e s o l u t i o n s ...............................................................................................

6k

X. C ry o s c o p ic c o n s ta n ts and h e a t s o f f u s i o n o f brom ine p e n ta ­
f l u o r i d e , io d in e p e n t a f l u o r i d e , and h y d ro g en f l u o r i d e ..............

67

X I. D e n s i t i e s and a v e ra g e m o la l volum es f o r h a lo g e n f l u o r i d e h y d ro g en f l u o r i d e s o l u t i o n s a t 25° C .......................................

77

X I I . C a l i b r a t i o n o f c e l l I u s in g a s o l u t i o n c o n ta in i n g O.3663
grains o f p o ta s s iu m c h l o r id e p e r l i t e r o f w a t e r ...........................

90

X I I I . C a l i b r a t i o n o f c e l l I u s in g a s o l u t i o n c o n ta in in g 0 . 7 U59
gram s o f p o ta s s iu m c h l o r id e p e r l i t e r o f w a t e r ..............................

95

XXV. C a l i b r a t i o n d a t a f o r c e l l I I .......................................................................

96

XV. D a ta f o r r e c a l i b r a t i o n o f c e l l I I .............................................................. 100

v ii

LIST OF TABLES - C ontinued

Page

XVI. D a ta f o r c a l i b r a t i o n o f c e l l U a t -7 8 °C ...............................................102
XVII* The s p e c i f i c c o n d u c ta n c e o f io d in e p e n t a f l u o r i d e a t v a r io u s
te m p e ra tu re s
.................................................................................................... 108
X V III. The s p e c i f i c c o n d u c ta n c e s o f brcanine p e n t a f l u o r i d e and
c h l o r i n e t r i f l u o r i d e a t v a r io u s t e m p e r a tu r e s ...........................
XIX. C o n d u ctan c es o f i o d i n e p e n ta f lu o r id e - h y d r o g e n f l u o r i d e
s o l u t i o n s , r u n B®.................................... ................................................

112
113

XX. C o n d u ctan ces o f io d in e p e n ta f lu o r id e - h y d r o g e n f l u o r i d e
s o l u t i o n s , r u n C ' . . . . . .......................... ........ .................. ............... ............. I l l ;
XXI. C o n d u ctan c es o f i o d i n e p e n ta f lu o r id e - h y d r o g e n f lu o r i d e
s o l u t i o n s w ith v e ry h ig h h y d ro g en f l u o r i d e c o n c e n t r a t i o n s . . 115
X X H . C o n d u c tan c es o f brom ine p e n ta f lu o r id e - h y d r o g e n f l u o r i d e
s o l u t i o n s , ru n E®.............................................................................................. 118
X X III. C o n d u ctan c es o f b ro m ine p e n ta f lu o r id e - h y d r o g e n f l u o r i d e
s o l u t i o n s , r u n F ' . . . .......................................................................................... 119
XXIV. C o n d u ctan ces o f c h l o r in e t r i f l u o r i d e - h y d r o g e n f l u o r i d e
s o l u t i o n s ............................................. ......................................................... ..
XXV. S p e c i f ic c o n d u c ta n c e s o f th e h a lo g e n f l u o r i d e s . . ...........................

122
125

XXVI. A p p are n t w e ig h t ch an g es f o r th e em pty s u s c e p t i b i l i t y t u b e ,
c a l i b r a t i o n I ................................................................ ...................................... 138
XXVII. F i r s t c a l i b r a t i o n o f th e s u s c e p t i b i l i t y t u b e ................................... 138
X X V III. The m a g n e tic s u s c e p t i b i l i t y o f io d in e p e n t a f l u o r i d e ....................U|2
XXIX. The m a g n e tic s u s c e p t i b i l i t y o f brom ine p e n t a f l u o r i d e ................. 1U3
XXX. A p p aren t w e ig h t c h an g es f o r t h e empty s u s c e p t i b i l i t y t u b e ,
sec o n d c a l i b r a t i o n ............................................................................................... lld i
XXXI. Second c a l i b r a t i o n o f th e s u s c e p t i b i l i t y t u b e ................................. I U 4
XXXII. The m a g n e tic s u s c e p t i b i l i t y o f c h lo r in e t r i f l u o r i d e ................... 1U5
X X X III. A p p a re n t w e ig h t ch an g es f o r t h e em pty s u s c e p t i b i l i t y t u b e ,
t h i r d c a l i b r a t i o n ........................................................ ...... ................................IJ4.6
XXXIV. T h ird c a l i b r a t i o n o f th e s u s c e p t i b i l i t y

t u b e .................................... lU 6

v iii

LIST OF TABLES - C o n tin u e d
XXXV. The m a g n e tic s u s c e p t i b i l i t y o f brom ine t r i f l u o r i d e

Page
Ili7

XXXVI. The m a g n e tic s u s c e p t i b i l i t i e s o f some l i q u i d f l u o r i d e s ............ ll*9

ix

LIST OF FIGURES

;ure

Page

1 . S ch e m atic d iag ram o f th e s t i l l , g as h a n d lin g , and s o l u t i o n
h a n d lin g sy stem f o r th e h a lo g e n f l u o r i d e s
..........................

11

2 . T y p ic a l v a p o r p r e s s u r e — c o m p o sitio n d ia g ra m ...................................

15

3 . D iagram o f t h e p r e s s u r e m e a s u rin g d e v i c e . . ......................................

19

li. Sample c a l i b r a t i o n c u rv e f o r th e p r e s s u r e m e a s u rin g d e v ic e .

20

5 . V apor p r e s s u r e - c o m p o s itio n d iag ram f o r brom ine p e n t a f l u o r i d e h y d ro g en f l u o r i d e s o l u t i o n s a t 0 , 1^ and 2 5 ° C . . . ........................ 23
6 . V apor p r e s s u r e - c o m p o s itio n diagram f o r io d in e p e n t a f l u o r i d e 25
h y d ro g en f l u o r i d e s o l u t i o n s a t 15° C ..................
7 . V apor p r e s s u r e - c o m p o s itio n diagram f o r c h lo r in e t r i f l u o r i d e h y d ro g en f l u o r i d e s o l u t i o n s a t 0°C .....................................................
27
8 . T y p ic a l c o o lin g c u rv e f o r a s o lv e n t c o n t a in in g a s m a ll
amount o f s o l u t e ..................................................... ............... . .........................

33

9 . T y p ic a l p h a s e d iag ram s f o r two com ponent s y s te m s ........................

35

1 0 . T y p ic a l c o o lin g c u rv e f o r a sam ple o f a two com ponent
sy stem w ith no compound f o r m a tio n
.........................................

37

X I . D iagram o f t h e f r e e z i n g p o i n t c e l l

ipL

..................................

1 2 . D iagram o f th e f r e e z i n g p o in t c e l l u s e d f o r brom ine p e n t a ­
f l u o r i d e ..................

hZ

1 3 . T herm ocouple c a l i b r a t i o n c u r v e .................................................................

U6

l h . D iagram o f t h e a p p a r a tu s f o r th e c a l i b r a t i o n p o i n t a t -78°C

hi

15 . D iagram o f t h e i c e - p o i n t t u b e ...................................................................

J48

1 6 . D iagram o f t h e p o te n tio m e te r and b u c k in g v o lta g e a p p a r a tu s .

h9

1 7 . Some r e p r e s e n t a t i v e c o o lin g c u rv e s f o r io d in e p e n t a f l u o r i d e h y d ro g en f l u o r i d e s o l u t i o n s ........................................................................ 5U
1 8 . Some r e p r e s e n t a t i v e c o o lin g c u rv e s f o r io d in e p e n t a f l u o r i d e h y d ro g en f l u o r i d e s o l u t i o n s .........................................
55
1 9 . P h ase d iag ram o f t h e sy ste m io d in e p e n ta f lu o r id e - h y d r o g e n
f l u o r i d e ....................................................................................................................

56

LIST OF FIGURES - C ontinued

Page

2 0 . D e t a i l o f t h e p h a se diagram o f th e io d in e p e n t a f l u o r i d e h y d ro g en f l u o r i d e sy stem show ing p o s s i b l e p e r i t e c t i c
p o i n t ............................................................................................

57

2 1 . Some r e p r e s e n t a t i v e c o o lin g c u rv e s f o r b rom ine p e n ta ­
flu o rid e -h y d ro g e n * f l u o r i d e s o l u t i o n s .................................................

59

2 2 . P h ase d iag ram o f t h e sy stem brom ine p e n ta f lu o r id e - h y d r o g e n
flu o rid e
..............................................................................

60

2 3 . D e t a i l o f th e p h a s e diagram o f th e sy stem brom ine p e n t a ­
f lu o r id e - h y d r o g e n f l u o r i d e show ing a p o s s i b l e s o l i d p h a s e
t r a n s i t i o n .........................................................................................

61

2h . C o o lin g cu rv e f o r p u re io d in e p e n t a f l u o r i d e .................................

63

2 5 . D e t a i l o f th e p h a se diagram o f th e h y d ro g en f l u o r i d e p o ta s s iu m f l u o r i d e s y s te m ..........................................................................

65

2 6 . The p y c n o m e te r....................................................................................................

76

2 7- D e n s i t i e s o f t h e h y d ro g en f l u o r i d e s o l u t i o n s o f same
h a lo g e n f l u o r i d e s ..................................................................

79

2 8 . S im p lif ie d d iag ram o f t h e c o n d u c ta n c e b r i d g e . . . . . . .................

85

2 9 . D iagram o f c o n d u c ta n c e c e l l I ...........................................

87

3 0 . D iagram o f c o n d u c ta n c e c e l l I I .................... ... ......................................

88

3 1 . S p e c i f ic c o n d u c ta n c e v e r s u s te m p e r a tu re f o r a s ta n d a r d
p o ta s s iu m c h l o r id e s o l u t i o n (0 .3663 gram s p e r l i t e r o f
w a te r)
..................................

93

3 2 . C a l i b r a t i o n c u rv e f o r c o n d u c ta n c e c e l l

I . ....................................

9ii

3 3 . S p e c i f i c c o n d u c ta n c e v e r s u s te m p e r a tu re f o r 0 .0 0 1 N
p o ta s s iu m c h l o r i d e s o l u t i o n ......................................................................

97

3 ^ . C a l i b r a t i o n c u rv e f o r c o n d u c ta n c e c e l l

98

I I ....................................

35- The g l a s s c o n d u c ta n c e c e l l ...........................................................................101
3 6 . The m ix in g sy stem f o r brom ine p e n t a f l u o r i d e s o l u t i o n s

103

3 7 . S p e c i f i c c o n d u c ta n c e v e r s u s te m p e r a tu re f o r io d in e p e n t a ­
f l u o r i d e ( ru n A ) ..................................................................................................109

LIST OF FIGURES - C ontinued

Page

38. S p e c if ic
flu o r id e

c o n d u c ta n c e
(ru n B )

v ersu s

te m p e r a tu re f o r io d in e

p e n ta ­
110

39. S p e c if ic
f lu o rid e

c o n d u c ta n c e
(ru n C )

v e rsu s

te m p e r a tu re f o r io d in e

p e n ta ­
Ill

hO. M o lar c o n d u c ta n c e v e r s u s s q u a re r o o t o f t h e m o l a r i t y o f
h y d ro g e n f l u o r i d e i n io d in e p e n ta f lu o r id e - h y d r o g e n f l u o r i d e
s o l u t i o n s a t 25°C
.........................................
116
111. P e r c e n t change i n c o n d u c ta n c e o f io d in e p e n t a f l u o r i d e h y d ro g e n f l u o r i d e s o l u t i o n s a t 20°C
................................

117

1*2. C o n d u c ta n c e -c o n c e n tr a tio n r e l a t i o n s h i p s f o r brom ine p e n t a ­
f lu o r id e - h y d r o g e n f l u o r i d e s o l u t i o n s a t v a r io u s
120
tem p e r a t u r e s ..................
1*3. M o lar c o n d u c ta n c e v e r s u s t h e s q u a re r o o t o f th e m o l a r i t y
o f h y d ro g en f l u o r i d e f o r h y d ro g en f lu o r id e - b r o m in e p e n ta ­
f l u o r i d e s o l u t i o n s a t 25°C ....................................................................... 121
1*1*. C o n d u c ta n c e —c o n c e n tr a tio n r e l a t i o n s h i p s f o r c h lo r in e t r i ­
f l u o r i d e - h y d r o gen f l u o r i d e s o l u t i o n s a t two d i f f e r e n t
t e m p e r a t u r e s .............................................................
123

h$. M o lar c o n d u c ta n c e v e r s u s th e s q u a re r o o t o f th e m o l a r i t y
o f h y d ro g e n f l u o r i d e i n c h l o r in e t r i f l u o r i d e - h y d r o gen
f l u o r i d e s o l u t i o n s 25°C ................................................

12h

1*6. D iagram o f th e Gouy m ag n etic b a l a n c e ....................................................136

hi* D iagram o f th e V ycor s u s c e p t i b i l i t y tu b e and d i s t i l l i n g
a p p a r a t u s ..................

137

1*8. C a l i b r a t i o n c u rv e f o r th e Gouy b a l a n c e

139

.........................

x ii

LIST OF PLATES
PLATE

F o llo w in g Page

1 . The s t i l l , g a s - h a n d l i n g , and s o l u t i o n h a n d lin g system
f o r th e h a lo g e n f l u o r i d e s ..............................................................................

11

2 . The p r e s s u r e m e a s u rin g d e v i c e .....................................................................

18

3 . The s o l u t i o n m ix in g s y s te m .................................... . . . . . ...........................

20

h . The f r e e z i n g p o i n t c e l l . . . . . ...............

bZ

5 . C on d u ctan ce c e l l H . . . . . .................................................................................

86

1

X

INTRODUCTION

The tre m e n d o u s p o s t- w a r grow th i n th e f i e l d o f f l u o r i n e c h e m is tr y
a s a r e s u l t o f t h e i n c r e a s i n g u s e and a v a i l a b i l i t y o f f lu o r o c a r b o n s ,
h a lo g e n f l u o r i d e s , and in o r g a n ic f l u o r i d e s , b o th i n i n d u s t r y and i n
th e program o f th e A tom ic E n erg y C om m ission, h a s c r e a t e d an i n c r e a s i n g
i n t e r e s t i n t h e p h y s i c a l p r o p e r t i e s o f th e h a lo g e n f l u o r i d e s and th e
v a r i o u s h a lo g e n f l u o r i d e s y s te m s ,
A d e t a i l e d s tu d y o f t h e p h y s ic a l p r o p e r t i e s o f th e h a lo g e n f l u o r i d e s
w as c o n s id e r e d t o b e i n o r d e r , and t h e r e f o r e th e d e s ig n and c o n s t r u c t i o n
o f e q u ip m e n t f o r t h e h a n d l i n g , p u r i f i c a t i o n and s tu d y o f th e h a lo g e n
f l u o r i d e s an d t h e i r h y d ro g e n f l u o r i d e s o l u t i o n s was u n d e r ta k e n .

As w i l l

b e d e s c r i b e d i n d e t a i l i n t h i s w o rk , s t u d i e s w ere made o f t h e m a g n e tic
s u s c e p t i b i l i t i e s o f c e r t a i n p u r e h a lo g e n f l u o r i d e s .

C o n d u c ta n c e , c ry o ­

s c o p ic and v a p o r p r e s s u r e s t u d i e s o f th e hyd ro g en f l u o r i d e s o l u t i o n s o f
t h e s e compounds w ere a l s o m ade.
No p r e v io u s w ork h a s b een r e p o r te d on t h e m a g n e tic s u s c e p t i b i l i t i e s
o f t h e s e com pounds.

T he e l e c t r i c a l c o n d u c t i v i t i e s o f t h e h a lo g e n f l u o r i d e s

h av e b e e n m easu red u s i n g m a t e r i a l o f unknown p u r i t y b u t no d a t a have b e e n
r e p o r t e d f o r th e c o n d u c ta n c e s o f t h e h y d ro g en f l u o r i d e s o l u t i o n s o f t h e
h a lo g e n f l u o r i d e s ,

T h e re a re same c r y o s c o p ic d a t a o n th e p u re compounds

and on b i n a r y sy ste m s o f b rom ine t r i f l u o r i d e and c e r t a i n m e t a l l i c s a l t s ,
b u t none on t h e h y d ro g en f l u o r i d e s o l u t i o n s o f t h e h a lo g e n f l u o r i d e s .
V apor p r e s s u r e d a t a a r e a v a i l a b l e f o r th e p u re h a lo g e n f l u o r i d e s , b u t
n o t f o r t h e i r h y d ro g en f l u o r i d e s o l u t i o n s .

2

The e x tr e m e ly h ig h r e a c t i v i t y o f th e h a lo g e n f l u o r i d e s made th e
u s e o f s p e c i a l h a n d lin g m ethods and h ig h ly r e s i s t a n t m a t e r i a l s n e c e s s a r y .
*
I n t h i s w ork f u l l u s e was made o f t h e r e s i s t a n t p r o p e r t i e s o f M o n el,
n i c k e l , f l u o r i n a t e d p o ly e th y le n e p l a s t i c s , and q u a r t z .

* T ra d e m ark o f t h e I n t e r n a t i o n a l N ic k e l Company

3

II

HISTORICAL SUMMARY

A . The H alo g en F lu o r id e s
A lth o u g h o u r know ledge o f th e p r o p e r t i e s o f th e h a lo g e n f l u o r i d e s
h a s made s i g n i f i c a n t s t r i d e s s in c e th e end o f W orld War I I , t h e s e com­
p o u n d s hav e b e e n known f o r seme t im e .

Kammerer1 p r o b a b ly p r e p a r e d

i o d i n e p e n t a f l u o r i d e a s e a r l y a s 1 8 6 2 , b u t th e p r e p a r a t i o n was p la c e d on
a p r a c t i c a l b a s i s by M o is s a n .2

The m a jo r s h a r e o f th e e a r l y w ork on th e

h a lo g e n f l u o r i d e s was done b y R u ff and h i s c o -w o rk e rs who e i t h e r d i s ­
c o v e r e d , o r im p ro v e d u p o n , t h e p r e p a r a t i o n o f s e v e n o f th e com pounds,
and s t u d i e d many o f t h e i r p h y s ic a l and c h e m ic a l p r o p e r t i e s . 3 ” 11
T h e re a r e s e v e n known s t a b l e h a lo g e n f l u o r i d e s , nam ely c h l o r i n e
m o n o f lu o r id e , c h l o r i n e t r i f l u o r i d e , brom ine m o n o flu o r id e , brom ine t r i ­
f l u o r i d e , b ro m in e p e n t a f l u o r i d e , io d in e p e n t a f l u o r i d e , and io d in e h e p ta flu o rid e ,

M ary o f t h e i r p h y s i c a l p r o p e r t i e s a r e a l r e a d y known.

T h e re

a r e s e v e r a l good r e v ie w s on t h e s u b j e c t 12" 14 and a c h a p te r b y B ooth and
P in k s to n h a s b e e n d e v o te d t o th e s e compounds i n Simons® F l u o r in e C h e m is try .
T h is d i s s e r t a t i o n i s p r i m a r i l y c o n c e rn e d w ith c r y o s c o p ic , c o n d u c t­
a n c e , and v a p o r p r e s s u r e s t u d i e s o f th e h a lo g e n f l u o r i d e s and t h e i r
h y d ro g e n f l u o r i d e s o l u t i o n s , and m a g n e tic s u s c e p t i b i l i t i e s o f t h e p u r i ­
f i e d h a lo g e n f l u o r i d e s .

O n ly w r k w hich i s r e l a t e d t o th e s e t o p i c s w i l l

b e d is c u s s e d h e r e .
The c r y o s c o p ic d a t a w h ich a r e a v a i l a b l e f o r th e h a lo g e n f l u o r i d e s
a r e l i m i t e d a lm o s t e x c l u s i v e l y t o the compounds themselves, and do n o t ,

h

i n g e n e r a l , e x te n d t o t h e i r s y s te m s w ith o t h e r s u b s t a n c e s .
o n ly i n f o r m a t i o n a v a i l a b l e , o t h e r th a n d a t a o b ta in e d i n t h i s

O f te n , th e
la b o ra to ry ,

i s t h e o r i g i n a l d a t a o f R u ff and h i s c o - w o r k e r s .
E u t e c t i c p o i n t s a t 3 .1 and -O .l;0 C w ere o b s e rv e d b y H a e n d le r 17 f o r
b i n a r y s y ste m s o f b rom ine t r i f l u o r i d e w ith barium f l u o r i d e and sodium
f lu o r id e , re s p e c tiv e ly .

T he f r e e z i n g p o i n t s r e p o r t e d i n t h e l i t e r a t u r e

f o r t h e h a lo g e n f l u o r i d e s a r e g iv e n i n T a b le X.
The c o n d u c ta n c e s o f m o st o f th e h a lo g e n f l u o r i d e s have b e e n r e p o r t e d
p r e v i o u s l y and t h e v a lu e s o b ta in e d a r e shown i n T a b le I .

The c o n d u c ta n c e s

o f b ro m in e t r i f l u o r i d e and b ro m in e p e n t a f l u o r i d e have b e e n r e p o r t e d t o
h a v e n e g a tiv e te m p e r a tu r e c o e f f i c i e n t s .

T h is h a s b e e n a t t r i b u t e d , a t

l e a s t i n t h e c a s e o f b ro m in e t r i f l u o r i d e , t o th e r m a l i n s t a b i l i t y o f th e
io n s . i ® , 19
On t h e b a s i s o f t h e in f o r m a tio n a v a i l a b l e on th e p r o p e r t i e s o f
i o d in e p e n t a f l u o r i d e and b ro m in e t r i f l u o r i d e a s s o l v e n t s , 20" 22 th e
c o n d u c t i v i t i e s o f th e s e compounds have b een a t t r i b u t e d t o th e s e l f io n iz a tio n e q u ilib ria
2BrFa

-

B rF 2+

+ B rF 4~

and
2 IF 6

*

IF 4

+

IF 6

The e x i s t e n c e o f compounds su c h a s KBrF4 , K lF6 , B rF3[SbF6 ] , and IF 4 [S bF 6 ]
le n d s s u p p o rt to t h i s h y p o th e s is .
R e c e n tly D . F . S m ith 24 h a s shown t h a t t o a v e r y s m a ll d e g r e e , a
o n e - to - o n e c o m p le x ,

h y d ro g e n f l u o r i d e - c h l o r i n e t r i f l u o r i d e (RF»CXF3) ,

i s fo rm ed i n t h e v a p o r s t a t e .

No e v id e n c e f o r com plexes o r in t e r m e d i a t e

5

TABLE I
THE SPECIFIC CONDUCTANCES AND FREEZING POINTS OF THE HALOGEN FLUORIDES
AND THEIR SOLUTIONS WITH OTHER COMPOUNDS
AS REPORTED IN THE LITERATURE*

S p e c if ic
C o n d u ctan ce
ohms“ 1cin":t

F r e e z in g
P o in t
°C

Compound

C1F

- 1 5 5 .6

16)

C lF a

- 8 2 .6

( 10)

B rF 3

8 .7 7 (1 6 )

BrFg

if

7

—

3 x lO - 9 a t ? °C

113)

8 .0 x 10“ 3 a t 25°C

(1 8 )

- 6 1 .3

17)

8 .3 x 1 0 '7 a t ? °C

(19)

9 .6

(9 )

1 .9 2 x 10"® a t 25°C

(1 2 )

6

(1 1 )

—

BrF6 - HF ^ e q u im o la r)

—

1 x 10“ 3 a t ?°C

BrFg - KF

—

I n c r e a s e s m a rk e d ly upon
(18)
a d d i t i o n o f KF

B rF 3

—

I n c r e a s e s m a rk e d ly upon
a d d i t i o n o f SbFe
(18)

IF 6 - KF

—

I n c r e a s e s m a rk e d ly upon
a d d i t i o n o f KF
(2 2 )

IF e - KF

—

No n o t i c e a b l e change
upon a d d i t i o n o f KF

SbF3

IF 6 - SbFe

—

(1 9 )

(1 2 )

I n c r e a s e s m a rk e d ly upon
a d d i t i o n o f SbFQ
(22)

* R eferen ces a re in d ic a te d i n p a r e n th e s e s .

6

coin p o u n d s was fo u n d i n a s tu d y o f th e l i q u i d - s o l i d e q u i l i b r i a i n th e
b ro m in e -b ro m in e t r i f l u o r i d e s y s te m ;36 l i q u i d i r r a n i s c i b i l i t y and th e
a b s e n c e o f s o l i d s o l u t i o n w ere o b s e rv e d .
The s p e c i f i c c o n d u c ta n c e o f a s i n g l e e q u ira o la r s o l u t i o n o f brom ine
t r i f l u o r i d e - h y d r o g e n f l u o r i d e was fo u n d by Hyman, Andrews and K a tz 19
t o b e a p p r o x im a te ly 1 x 10

-.3

mho p e r c e n t i m e t e r .

A n e g a tiv e c o n d u c t-

a n c e - te m p e r a tu r e c o e f f i c i e n t was o b s e rv e d w ith t h i s s o l u t i o n .
T h e re a r e no v a p o r p r e s s u r e d a ta a v a i l a b l e f o r h a lo g e n f l u o r i d e
s o l u t i o n s o f o t h e r com pounds, and no m a g n e tic s u s c e p t i b i l i t y m easurem ents
h a v e b e e n r e p o r t e d on t h e h a lo g e n f l u o r i d e s .

B.

H ydrogen F lu o r id e

H ydrogen f l u o r i d e was f i r s t o b ta in e d b y M a rg g ra ff i n 176826 and
f i r s t c h a r a c t e r i z e d i n 1771 b y S c h e e le . 27

I t i s p re p a re d i n d u s t r i a l l y

b y t h e r e a c t i o n o f s u l f u r i c a c i d w ith f l u o r s p a r a f t e r w h ich th e r e a c t i o n
p r o d u c t i s co n d en sed and d i s t i l l e d .

H ig h ly p u r i f i e d h y d ro g e n f l u o r i d e

may b e o b ta in e d from t h e d e c o m p o s itio n o f p o ta s s iu m b i f l u o r i d e .
The p h y s i c a l p r o p e r t i e s o f h y d ro g en f l u o r i d e h av e b e e n s t u d i e d
r a t h e r e x t e n s i v e l y and t h e r e i s an e x c e l l e n t r e v ie w b y S im ons. le b t 16C
A nhydrous l i q u i d h y d ro g en f l u o r i d e re s e m b le s w a te r and ammonia
i n i t s p h y s ic a l p r o p e r t i e s .

I t s b o i l i n g p o i n t i s above t h a t o f h y d ro g en

c h l o r i d e j u s t a s t h e b o i l i n g p o i n t s o f w a te r and ammonia a r e above
th o s e o f h y d ro g e n s u l f i d e and p h o s p h in e , and i t s d i e l e c t r i c c o n s ta n t
( 8 3 . 6 a t 0°C) i s r e l a t i v e l y h i g h . 26

Sim ons29 h a s r e p o r t e d t h a t th e

l i q u i d d e n s i t y i s g iv e n a s a f u n c t i o n o f te m p e r a tu re by th e r e l a t i o n

7

d * 1 .0 0 2 - ,0 0 2 2 6 2 £ t + .0 0 0 0 0 3 1 2 5 t3
w here d i s gpn./m l. and t i s t h e te m p e r a tu r e i n d e g r e e s C e n tig r a d e .

The

m o st r e c e n t v a p o r p r e s s u r e d a t a b e tw e e n 0 ° and 105>°C a r e r e p r e s e n t e d by
e i t h e r o f t h e f o llo w in g r e l a t i o n s h i p s 30
l o g P - 0 .3 0 0 3 6 -

■

or
l o g P - 1 .9 1 1 7 3 - 9 1 8 .2 l* /t -3 .2 1 5 ^ 2 lo g t
w here P i s t h e v a p o r p r e s s u r e i n mm. o f Hg and t i s th e te m p e r a tu r e i n
d e g re e s C e n tig ra d e .
The p h y s i c a l p r o p e r t i e s o f h y d ro g e n f l u o r i d e i n d i c a t e t h a t i t i s
a m o st u n u s u a l l i q u i d .

I t s h ig h d i e l e c t r i c c o n s ta n t and a b i l i t y t o form

v e r y h i g h l y c o n d u c tin g s o l u t i o n s 1615 i n d i c a t e t h a t i t i s a p o l a r l i q u i d ,
y e t i t s low v i s c o s i t y ( 0 .2 5 6 c e n t i p o i s e a t 0°C) and lo w s u r f a c e te n s i o n
( 1 0 .1 d y n e s/c m . a t 0 °C )a ° i n d i c a t e t h a t t h e l i q u i d i s n o n - p o la r .
I n t h e g a se o u s s t a t e h y d ro g e n f l u o r i d e h a s been fo u n d t o b e a
h i g h l y im p e r f e c t g a s .

A s s o c ia tio n o c c u rs t o a r a t h e r l a r g e e x t e n t and

h a s b e e n i n v e s t i g a t e d b y Sim ons3x and o t h e r s .

T h ere h a s b e e n a c o n s id e r ­

a b le am ount o f dLssagrem ent among th e v a r io u s w o rk ers a s t o w hich p o ly m ers
a r e t h e m o st i m p o r t a n t .

Some v a p o r d e n s i t y w ork seem s t o i n d i c a t e t h a t

a s i x membered r i n g p r e d o m in a te s , where a s d i p o l e moment s t u d i e s 32 *33 and
X -ra y s t u d i e s 34” 36 seem t o i n d i c a t e a c h a i n - l i k e s t r u c t u r e .
R e c e n tly J o h n s to n

37

h a s m easu red th e h e a t c a p a c i t y , h e a t o f f u s i o n

and h e a t o f v a p o r i z a t i o n o f liydrogen f l u o r i d e .

No t r a n s i t i o n s s u c h as

a r e o b s e rv e d w ith th e o t h e r h y d ro g en h a l i d e s w ere fo u n d .

The h e a t o f

f u s i o n a t t h e m e l t i n g p o i n t t-8 3 .3 7 ° C ) was fo u n d t o b e 9 3 8 .6 c a l o r i e s
p e r m ole*

J o h n s t o n 8s m e ltin g p o i n t v a lu e i s i n s l i g h t d is a g re e m e n t

w ith p r e v i o u s l y r e p o r t e d v a lu e s o f - 8 3 .0 7 and -

8

3

Compa r i s on

o f e n tr o p y v a l u e s from h e a t c a p a c i t y m easurem ents and s p e c tr o s c o p ic
d a t a show ed a l a r g e d is c r e p a n c y w hich was a c c o u n te d f o r by assu m in g th e
g a s t o b e a m ix tu r e o f m onom er, d im e r , t r i m e r , e t c . , a s a co n seq u en ce
o f h y d ro g e n b o n d in g .

The r e c e n t s p e c tr o s c o p ic w ork o f D, F . S m ith 34

seem s t o i n d i c a t e , h o w e v e r, t h a t a t low te m p e r a tu r e s o n ly t h e hexam er
i s im p o r ta n t i n th e v a p o r s t a t e , and t h a t t h e r e i s no e v id e n c e f o r
p o ly m e rs o t h e r t h a n th e t e t r a in e r and h ex am er.

9

III

PREPARATION AND HANDLING OF MATERIALS

The s tu d y o f t h e h a lo g e n f l u o r i d e s h a s i n c r e a s e d g r e a t l y i n th e
p o s t- w a r p e r i o d , p a r t l y a s a r e s u l t o f t h e a v a i l a b i l i t y o f m a t e r i a l s
w h ich a r e h i g h l y r e s i s t a n t t o t h e a c t i o n o f t h e h a lo g e n f l u o r i d e s .
The m o st im p o r ta n t o f th e s e m a t e r i a l s a r e f l u o r i n a t e d p o ly e th y le n e
-x
p l a s t i c s s u c h a s f lu o r o t h e n e and T e f lo n .
I n o r d e r t o o b t a i n t h e h a lo g e n f l u o r i d e s i n t h e p u re f o r m , i t i s
n e c e s s a r y t h a t th e y b e s e p a r a te d i n some m anner from v o l a t i l e and non­
v o l a t i l e i m p u r i t i e s , and t h a t th e y b e s t o r e d i n su c h a way t h a t th e y
do n o t become c o n ta m in a te d .

The p r i n c i p a l s o u rc e s o f c o n ta m in a tio n

a r e u s u a l l y c o r r o s i o n p r o d u c ts and d e c o m p o s itio n p r o d u c ts from th e r e ­
a c t i o n w ith w a te r v a p o r .

I n o r d e r t o overcam e th e above d i f f i c u l t i e s

a vacuum s y s te m , w hich h a s b e e n d e s c r ib e d p r e v i o u s l y , 12 was c o n s tr u c t e d .
T h is s y s te m , w hich i s i l l u s t r a t e d i n F ig u re 1 and P l a t e 1 , p r o v id e d a
m eans f o r f r a c t i o n a l d i s t i l l a t i o n o f th e im pure h a lo g e n f l u o r i d e tin d er
i t s own p r e s s u r e o r i n an i n e r t a tm o s p h e re .

I t a l s o p r o v id e d a means

o f p e rfo rm in g s u c h o p e r a t i o n s a s t r a p - t o - t r a p d i s t i l l a t i o n s , v a p o r o r
l i q u i d p h a s e t r a n s f e r s , and p r e p a r a t i o n o f h y d ro g e n f l u o r i d e s o l u t i o n s
o f t h e h a lo g e n f l u o r i d e s .

The vacuum system was a ls o p r o v id e d w ith a

tu b e c o n t a i n i n g c o b a l t i c f l u o r i d e th ro u g h w hich th e hydrogen f l u o r i d e
from th e ta n k was p a s s e d i n o r d e r t o rem ove m o is t u r e .
I n o r d e r t o p r o v id e t h e maximum r e s i s t a n c e t o c o r r o s io n tiie vacuum
l i n e was c o n s tr u c t e d a lm o st e n t i r e l y o f n i c k e l and M onel e x c e p t f o r th e
E . I . d u P o n t de Nemours and C o.

10

s t i l l h e a d , s to r a g e c o n t a i n e r s and s to r a g e tu b e s w hich were c o n s tr u c te d
° f f lu o r o t h e n e and T e f l o n .

The v a lv e s w ere c o n s tr u c te d o f n i c k e l , w ith

p h o s p h o r-b ro n z e b e llo w s and f lu o r o th e n e g a s k e t s , e x c e p t on th e s t i l l
t a k e - o f f sy stem w here v a lv e b o d ie s c o n s tr u c t e d o f f lu o r o th e n e r e p la c e d
th o s e o f n i c k e l .

I n some p la c e s s m a ll v a lv e s c o n ta in in g b r a s s b e llo w s

w ere u s e d .
The g e n e r a l p ro c e d u re f o r th e p u r i f i c a t i o n o f io d in e p e n t a f l u o r i d e
and b ro m in e p e n t a f l u o r i d e i s a s f o llo w s :

th e c o m m e rc ia lly a v a i l a b l e

■tt

h a lo g e n f l u o r i d e was c o n d en sed o r p o u re d i n t o a f lu o r o th e n e c o n ta i n e r
w h ich c o u ld b e s e a l e d , and from w hich t h e m a t e r i a l c o u ld be s ip h o n e d i n t o
th e s t i l l p o t.

I n t h i s c o n t a i n e r th e m a t e r i a l was p r e t r e a t e d w ith

c h lo rin e t r i f l u o r i d e .

T h is r e a c t e d w ith any io d in e o r brom ine id iic h

m ig h t hav e b e e n p r e s e n t t o g iv e io d in e p e n t a f l u o r i d e , o r brom ine p e n ta ­
f l u o r i d e , and c h l o r i n e .

The m ix tu re was th e n p u l l e d th ro u g h a n ic k e l

tu b e i n t o t h e s t i l l p o t w here as much o f th e h ig h ly v o l a t i l e com ponents
as p o s s i b l e was pumped o f f .

The m ix tu re re m a in in g was th e n f r a c t i o n a l l y

d i s t i l l e d , t h e c o n s ta n t b o i l i n g p o r t i o n b e in g c o l l e c t e d d i r e c t l y i n th e
l a r g e f lu o r o t h e n e s to r a g e c o n t a in e r a s shown i n F ig u r e 1 and P l a t e 1 .
T he p ro c e d u re s u s e d f o r p u r i f y i n g and h a n d lin g b rom ine t r i f l u o r i d e
and c h l o r i n e t r i f l u o r i d e a re d e s c r ib e d i n l a t e r s e c t io n s w hich d e a l w ith
t h e e x p e rim e n ts i n w hich t h e s e compounds w ere u s e d .

The d i f f e r e n t ty p e s

o f e x p e rim e n ts p e rfo rm e d i n t h i s work r e q u i r e d v a r io u s m ethods o f s o lu ­
tio n p re p a ra tio n .

The s p e c i f i c p r o c e d u re s u s e d w i l l be d e s c r ib e d i n

t h e s e c t i o n s w h ere th e y a r e a p p l i c a b l e .
■» H arshaw C h em ical Co.

IX

J

I

To a u x i l i a r y
vacuum >k l i n e

To b a c k
o f hood

To pump

-o l ^ / x x T o

^

\K
To v ap o r
p re ssu re
m e a su rin g
d e v ic e

P re ssu re

' re g u la to r
^ - ^ T o f lu o r o l u b e
o i l m anom eter

To b a c k o f
hood o r t o
vacuum l i n e

F ig u r e 1 . S ch em atic d iag ram o f th e s t i l l , g as ■‘h a n d lin g , and s o l u t i o n h a n d lin g sy ste m f o r h a lo g e n f l u o r i d e s : A, t o a i r d r y in g s y s te m ; B , C,
and D , t o t a n k s o f liy d ro g en f l u o r i d e , c h l o r in e t r i f l u o r i d e , and brom ine
p e n t a f l u o r i d e ; E , e x t r a l i n e o u t l e t ; F and G, aluminum t r a p s f o r h a n d l­
i n g and s t o r i n g m a t e r i a l s ; H , c o p p e r ta n k f o r s to r a g e o f g a s e s ; X and
J , H e l i c o i d p r e s s u r e g a u g e s ; K, c o b a l t t r i f l u o r i d e c o n t a i n e r ; L , f l u o r o ­
th e n e s to r a g e t u b e ; H , s t i l l h e a d ; fl, s t i l l ; 0 , a n d P , s to r a g e c o n t a i n e r s ;
q , p r e t r e a t i n g c o n t a i n e r ; B and S , tu b e s o r a p p a r a tu s i n w hich s o lu t i o n s
a r e p r e p a r e d ; T , aluminum s to r a g e tu b e f o r m a t e r i a l s t o be d i s c a r d e d ;
U, s t i l l p o t ; ® l a r g e v a lv e s w ith p h o sp h o r b ro n a e b e llo w s ; • s m a ll
v a l v e s w ith b r a s s b e llo w s .

KLate 1. The s t i l l , gas-handLing and solution
system for the halogen f lu o r id e s

h an d lin g

12

IV

VAPOR PRESSURE STUDIES OF HALO(J£N FLUGRIDB-ttlDROGEN FLUORIDE
SOLUTIONS

s&
A. T h e o r e t i c a l A s p e c ts
W henever a s u b s ta n c e i s d is s o lv e d i n a s o lv e n t th e v a p o r p r e s s u r e
o f t h e s o l v e n t i s lo w e r e d .

I n 186b F . M. R a o u lt was a b le t o show t h a t

f o r a c o n s id e r a b l e number o f s o l u t e s an d s o lv e n ts th e e q u a tio n

-R'-ZJU
p*
was a p p ro x im a te ly f o llo w e d .

*

na
n3 + nx

»

Xa

The p r e s s u r e s o f t h e p u re s o lv e n t and th e

s o l v e n t i n s o l u t i o n a r e p* and p ,

r e s p e c t i v e l y ; nj, and n 3 a r e th e number

o f m o les o f s o l u t e and s o l v e n t i n

th e s o l u t i o n , r e s p e c t i v e l y ; and x 3 i s

th e m ole f r a c t i o n o f t h e s o l u t e .
By s u b t r a c t i n g u n i t y from e a c h s id e o f th e above e q u a t io n , i t i s
o b v io u s t h a t
P

«

-a
1 - x3 « x x

p*
w here

i s t h e m ole f r a c t i o n o f th e s o l v e n t .
The l a s t m e n tio n e d e q u a tio n i s known a s R a o u l t*s la w .

I t c a n be

s e e n t h a t i n t h i s i d e a l i z e d c a s e th e v a p o r p r e s s u r e o f a s o lv e n t i n a
s o lu tio n i s d ir e c tly p ro p o rtio n a l

t o i t s m ole f r a c t i o n .

I n t h e s tu d y o f l i q u i d m ix tu r e s an i d e a l s o l u t i o n i s d e f in e d
w hich o b ey s R a o u lt* s la w o v e r th e e n t i r e ra n g e o f c o n c e n t r a t i o n s .
two v o l a t i l e c o m p o n en ts, 1 and 2 , i f

a s one
For

13

Pi = Pi
o v e r th e e n t i r e ra n g e o f c o n c e n t r a t i o n s , th e n ta k in g th e lo g a r ith m o f
b o tli s i d e s and d i f f e r e n t i a t i n g w ith r e s p e c t t o x ^
x%

d ln P i
dxx

a n d , b y u s e o f t h e Duhem -M argules e q u a t io n ,
-1
dx2
I n t e g r a t i n g t h e l a t t e r e q u a tio n and n o tin g t h a t p 2 * p 2 when x 2 « 1 ,
Pa ° Pa x2
w hich i s R a o u lt* s la w f o r th e seco n d com ponent.
Thus i f a m ix tu re o f two c o m p le te ly m is c ib l e l i q u i d s b eh av es i d e a l l y
a p l o t o f t h e p a r t i a l p r e s s u r e o f e i t h e r com ponent s h o u ld be a s t r a i g h t
l i n e p a s s i n g th ro u g h t h e o r i g i n , a s shown i n F ig u r e 2 - a .

The t o t a l v ap o r

p r e s s u r e i s t h e sum o f th e p a r t i a l p r e s s u r e s , and i n th e i d e a l c a s e
w ould b e t h e t i e l i n e c o n n e c tin g p i and p i i n F ig u re 2 - a .
I t s h o u ld b e n o te d t h a t m ix tu re s w hich beh av e i d e a l l y a r e g e n e r a lly
fo u n d t o b e o n es i n w hich th e com ponents a r e s i m i l a r b o th p h y s i c a l l y
and c h e m ic a lly , s in c e i n t h e i d e a l s o l u t i o n th e r e s h o u ld be l i t t l e
d i f f e r e n c e b e tw e e n t h e e n v iro n m e n t o f a g iv e n com ponent i n th e p u re
l i q u i d and i n th e m i x t u r e .
The p r i n c i p a l r e a s o n t h a t a s o l u t i o n may n o t show i d e a l b e h a v io r
i s t h a t th e i n t e r m o l e c u l a r f o r c e s b etw een t h e d i f f e r e n t m o le c u le s may
be e i t h e r l a r g e r o r s m a l l e r t h a n t h e in te r m o le c u la r f o r c e s betw een th e
m o le c u le s o f th e p u re s u b s t a n c e s , le a d in g t o n e g a tiv e o r p o s i t i v e d e ­
v i a t i o n s from R a o u lt* s la w , r e s p e c t i v e l y .

1h

The ty p e o f v a p o r p r e s s u r e - c c s n p o s itio n diagram o b ta in e d when th e
d e v i a t i o n s from R a o u l t* s law a r e p o s i t i v e i s shown i n F ig u r e 2 - b .

It

s h o u ld b e n o te d t h a t th e p a r t i a l - p r e s s u r e c u r v e s f o r th e s o lv e n t a p p ro ach
i d e a l i t y a t i n f i n i t e d i l u t i o n , b u t th e t o t a l - p r e s s u re c u rv e does n o t .
The ty p e o f v a p o r p r e s s u re - c o m p o s itio n d iag ram o b ta in e d when th e r e
a r e n e g a tiv e d e v i a t i o n s from R a o u l t 1s law i s i l l u s t r a t e d i n F ig u r e 2 - c .
I n t h e i l l u s t r a t i o n s sh o w n , th e c u rv e s f o r th e t o t a l p r e s s u r e
show a maximum o r a minimum.

A t th e maximum o r minimum p o i n t s th e

v a p o r h a s th e same c o m p o s itio n a s th e l i q u i d and th e m ix tu re i s c a l l e d
an a a e o t r o p e .

The a z e o tr o p ic c o m p o sitio n depends on th e te m p e r a tu re .

A c t u a l l y t h e d e v i a t i o n s a r e g e n e r a l l y n o t so extrem e a s t o c a u se a
maximum o r a minimum.

15

Pi

o

Pi

T o ta l v

Pa

o
Pa

Pi
Pi

o

Pi
U)

F ig u r e 2 .

u)

T y p ic a l v a p o r p r e s s u re - c o m p o s itio n diagram

16

B . A p p a ra tu s and M ethod
The P r e s s u r e M e a su rin g D evice
D e s ig n .

The d e v ic e f o r m easurem ent o f th e v ap o r p r e s s u r e above a

m ix tu re o f h a lo g e n f l u o r i d e and h y d ro g en f l u o r i d e m ust o f c o u rs e b e
one w h ich w i l l n o t b e a f f e c t e d by th e h ig h r e a c t i v i t y o f th e s e com­
pounds.

I n t h i s w ork t h e d e v ic e w hich i s i l l u s t r a t e d i n F ig u re 3 and

P l a t e 2 was u s e d .

I t c o n s i s t s e s s e n t i a l l y o f th e p r e s s u r e - s e n s i t i v e
*
p a r t o f a H e lic o id gauge w hich i s m ounted i n su c h a m anner t h a t i t s

movement d u e t o p r e s s u r e w ith in t h e M onel B ourdon Tube may be a c c u r a t e l y
d e te rm in e d b y m eans o f a m ic ro m e te r s c re w .

In a c tu a l p ra c tic e th e re

was a m e ta l s h a f t a b o u t f o u r in c h e s lo n g s o ld e r e d t o th e t i p o f th e t u b e .
The m ic ro m e te r sc re w made c o n t a c t w ith a s i l v e r s t r i p s o ld e r e d t o th e
end o f t h e s h a f t .

Added s e n s i t i v i t y was p r o v id e d b y h a v in g th e t i p o f

t h e m ic ro m e te r s c re w and th e s h a f t a c t a s c o n t a c t s w hich opened and
c l o s e d th e c i r c u i t o f a m agic eye tu b e when c o n t a c t was made o r b r o k e n .
I n t h i s m annsr t h e p o i n t a t w hich c o n ta c t wa3 made c o u ld b e r e a d t o th e
n e a r e s t f i v e - t h o u s a n d t h s o f a m i l l i m e t e r ( 0 .0 0 5 m m .).
The gauge was p r o v id e d w ith tw o v a l v e s , one o f w hich p r o v id e d a
d i r e c t o u t l e t t o th e vacuum l i n e , and th e o t h e r o f w hich was a tta c h e d
d i r e c t l y t o th e tu b e c o n t a i n i n g th e s o l u t i o n .

The p r e s s u r e s e n s i t i v e

p a r t o f t h e gauge was e n c lo s e d i n a n i n s u l a t e d b o x w ith in w h ich a c o n s t a n t te m p e r a tu r e was m a in ta in e d by m eans o f a C en c o -d eK h o tin sk y
r e g u l a t o r and an e l e c t r i c l i g h t b u l b .
* A m erican C h a in and C a b le C o.
The C e n t r a l S c i e n t i f i c C o.

17

The H e l i c o i d gauge w hich was u s e d i n t h i s work was one w hich o r i g ­
i n a l l y gave a f u l l s c a l e d e f l e c t i o n o f l£ 0 0 mm. o f m e rc u ry , th e t o t a l
movement o f t h e t i p o f t h e B ourdon tu b e b e in g a b o u t it mm. o v e r th e f u l l
p re ssu re ra n g e .

T h is w ou ld g iv e a t h e o r e t i c a l s e n s i t i v i t y o f a b o u t

p l u s o r m in u s one m i l l i m e t e r o f m ercury*

I n a c t u a l p r a c t i c e i t was fo u n d

t h a t when c a l i b r a t i n g t h e in s tr u m e n t th e s e n s i t i v i t y was a b o u t p lu s o r
m in u s two mm. o f m e rc u ry .

When m e a s u rin g t h e v a p o r p r e s s u r e s o f s o lu ­

t i o n s t h e r e p r o d u c i b i l i t y was g e n e r a l l y o b s e rv e d t o b e p lu s o r m inus t h r e e
t o f i v e mm. o f m e rc u ry d e p e n d in g upon th e d i f f i c u l t y e n c o u n te re d i n b r in g ­
in g t h e s o l u t i o n i n t o e q u ilib r iu m w ith t h e v a p o r .
The s o l u t i o n was p l a c e d i n a f lu o r o th e n e tu b e m achined w ith a fe m a le
s t a n d a r d - t a p e r t o p ; th e m a tin g p lu g had a h o le d r i l l e d th ro u g h i t and a
n i c k e l tu b e w ith a f l a r e f i t t i n g th r e a d e d i n t o t h e h o le *

The f l a r e

f i t t i n g was a t t a c h e d d i r e c t l y t o th e e n tr a n c e v a lv e o f th e gauge a s
i l l u s t r a t e d i n F ig u re 3 .

A s m a ll T e flo n - c o v e re d m a g n e tic s t i r r e r was

p la c e d i n s i d e t h e t u b e .
C a lib ra tio n *

I n o r d e r t o c a l i b r a t e th e g a u g e , th e e n tr a n c e v a lv e

w h ich o r d i n a r i l y h e ld th e s o l u t i o n tu b e was a tta c h e d d i r e c t l y t o one arm
o f a d i f f e r e n t i a l m e rc u ry m an o m eter.
t o t h e vacuum l i n e .

The o th e r v a lv e rem a in e d a tta c h e d

The p r e s s u r e w i t h i n th e gauge was v a r ie d by chang­

i n g t h e p r e s s u r e w i t h i n t h e vacuum l i n e and was th e n r e a d d i r e c t l y from
th e m an o m eter.

The m ic ro m e te r screw was a d ju s t e d so t h a t i t j u s t con­

t a c t e d th e s i l v e r s t r i p on t h e end o f th e s h a f t and th e r e a d in g on th e
m ic ro m e te r s c a l e was re c o rd e d *
F ig u r e 1*.

A sam ple c a l i b r a t i o n c u rv e i s g iv e n i n

lb

S o l u t i o n P r e p a r a t i o n and P ro c e d u re
The h a lo g e n f l u o r i d e , t h e p u r i f i c a t i o n and s to r a g e o f w hich i s
d e s c r i b e d a b o v e , was s ip h o n e d d i r e c t l y from th e s to r a g e c o n t a i n e r ^ see
P l a t e 3) i n t o th e p r e v i o u s l y w eighed f lu o r o th e n e t u b e .

In th e case o f

c h l o r i n e t r i f l u o r i d e a c ru d e p u r i f i c a t i o n was o b ta in e d by d i s t i l l i n g
d i r e c t l y from t h e ta n k on t h e vacuum l i n e i n t o th e tu b e and th e n d i s t i l l ­
i n g o u t o f th e tu b e u n t i l t h e v a p o r p r e s s u r e became c o n s t a n t .

Dry a i r

was l e t i n t o t h e t u b e , th e v a lv e o v e r th e tu b e was c lo s e d and t h e l i n e
c le a n e d b y e v a c u a tin g and h e a t i n g .

The tu b e was th e n rem oved from th e

s t o r a g e c o n t a i n e r , c lo s e d w ith a p lu g , and w eighed on a T o r s io n B a la n c e .*
The c o n t e n t s o f t h e tu b e w ere f r o z e n w ith a Dry I c e - c a r b o n t e t r a c h l o r i d e c h lo ro fo rm b a th p la c e d aro u n d th e t u b e .

The assem b ly was th e n a t ta c h e d

t o t h e gauge and e v a c u a te d w h ile s t i l l f r o z e n .

A f te r e v a c u a tio n th e

v a lv e t o t h e vacuum l i n e was c l o s e d , and th e c o n te n ts w ere b r o u g h t t o
th e d e s i r e d te m p e r a tu re b y p l a c in g a Dewar f l a s k c o n ta in in g w a te r a t
t h a t te m p e r a tu r e aro u n d i t .
m ag n et o u t s i d e th e t u b e .

A g i t a t i o n was a c c o m p lish e d b y m oving a

When th e s c a l e r e a d in g became c o n s ta n t th e r e a d ­

i n g was t a k e n .
The f i r s t h y d ro g e n f l u o r i d e s o l u t i o n was p r e p a re d b y f r e e z i n g th e
c o n t e n t s o f th e tu b e a g a in and c o n d e n sin g h y d ro g en f l u o r i d e i n t o t h e tu b e
from t h e ta n k on t h e vacuum l i n e .

The w eig h in g and p r e s s u r e - m e a s u r in g

p r o c e d u r e s w ere i d e n t i c a l t o t h o s e i n d i c a t e d a b o v e .

T h is p ro c e d u re was

r e p e a t e d so t h a t i t was p o s s i b l e t o o b ta in m easurem ents o f s e v e r a l sam ples
o f h y d ro g e n f l u o r i d e s o l u t i o n from each sam p le o f h a lo g e n f l u o r i d e p r e p a r e d .
* The T o r s io n B a la n c e C o.

1?

To vacuum l i n e

110V

F ig u r e 3„ The p r e s s u r e m e a s u rin g d e v ic e s A, B ourdon t u b e , B ,
s o l u t i o n tu b e and m a g n e tic s t i r r e r ; C , m ic ro m e te r; D, p l a s t i c
r o d ; E , c i r c u i t d iag ram f o r t h e m ag ic-ey e tu b e ; F , te m p e r a tu r e
c o n t r o l s y s te m .

20

S c a le
R ea d in g
18.0

17.0

16.0
0

300

600

900

P r e s s u r e (nm . o f Hg)

F ig u r e i*. Sample c a l i b r a t i o n c u rv e f o r th e p r e s s u r e
m e a s u rin g d e v i c e .

21

C.

D ata and C a lc u l a ti o n s

E ach r u n i n d i c a t e d i n th e f o llo w in g t a b l e s was s t a r t e d w ith a s i n g l e
sam p le o f h a lo g e n f l u o r i d e .
The o b s e rv e d v a p o r p r e s s u r e s f o r s o l u t i o n s o f brom ine p e n t a f l u o r i d e
and h y d ro g e n f l u o r i d e a r e g iv e n i n T a b le I I and F ig u re 5 .

The o b se rv e d

v a p o r p r e s s u r e s f o r s o l u t i o n s o f i o d i n e p e n t a f l u o r i d e and h y d ro g en
f l u o r i d e a r e g iv e n i n T a b le I I I and F ig u re 6 , and th e o b s e rv e d v a p o r
p r e s s u r e s f o r s o l u t i o n s o f c h l o r in e t r i f l u o r i d e and h y d ro g en f l u o r i d e a r e
g iv e n i n T a b le IV and F ig u r e 7The b ro m in e p e n t a f l u o r i d e r u n s a t 2f?°C show l a r g e e r r o r s b e c a u s e
t h e te m p e r a tu r e was c l o s e t o room te m p e ra tu re and i t was n o t p o s s i b l e t o
c o n t r o l t h e te m p e r a tu re o f th e to p o f th e tu b e an d ta p e r e d p lu g .
The e r r o r i n d i c a t e d f o r each v a p o r p r e s s u r e v a lu e i s b a s e d upon th e
a c c u r a c y w ith w h ich t h a t p a r t i c u l a r r e a d in g c o u ld be re p ro d u c e d a f t e r
c h a n g in g t h e p r e s s u r e s l i g h t l y .
D.

D is c u s s io n o f th e R e s u lts

The v a p o r p r e s s u r e s o f th e h a lo g e n f lu o r id e - h y d r o g e n f l u o r i d e s o lu ­
t i o n s i l l u s t r a t e d i n F ig u r e s 5 , 6 , and 7 a l l show a m arked p o s i t i v e
d e v i a t i o n from R a o u lt* s la w .

I f i t i s p o s s i b l e to c o n s id e r th e brom ine

p e n t a f l u o r i d e s o l u t i o n s as a t y p i c a l c a s e , i t a ls o a p p e a rs t h a t t h e r e i s
a v e r y m arked i n c r e a s e i n t h i s d e v i a t i o n w ith i n c r e a s i n g te m p e r a tu r e .
I t i s a c t u a l l y q u i t e d i f f i c u l t t o draw d e f i n i t e c o n c lu s io n s from
t h e sh a p e o f t h e v a p o r p r e s s u r e c u rv e s b e c a u s e v e ry l i t t l e

i s known a b o u t

22

TABLE I I
THE VAPOR PRESSURES OF BROMINE PiENTAFLUORIDE-HIDROGEN FUJORIDE
SOLUTIONS AT 0 ,
and 2£°C

T e m p e ra tu re
°C

H o le P e r c e n t
HP

2 5 .0
2 5 .0
2 5 .0
2 5 .0
2 5 .0
2 5 .0

S un I *
0 ,0 0
2.1*0
3 .5 5
1 5 .0
3 7 .9
1*6 .2

2 5 .0
2 5 .0
2 5 .0

Hun 11*
17 .U
1*2.8
6 2 .0

81*6 £ 5
927 i 10
980 + 10

2 5 .0
2 5 .0
2 5 .0

Hun X U *
1 0 0 .0
8 7 .8
5 9 .3

920 1 10
1077 - 10
111*5 - 30

0 .0
0 .0
0 .0
0 .0
0 .0

Run IV
6 .6
£ l .2
6 9 .0
8 2 .1
9 1 .5

11*2
300
350
368
380

£
£
+

I

3
3
3
3
3

1 5 .0
0 .0
1 5 .0
0 .0

Run V
0 .6
0 .0
6 3 .3
6 3 .3

258
136
612
331*

£
£
£
£

3
3
6
6

0 .0
1 5 .0
1 5 .0
0 .0
1 5 .0

Hun VI
26.8"
2 6 .8
1*7.5
7 8 .6
7 8 .6

21*0
505
585
365
61*0

£
£
£
£
i

5
10
5
10
5

P re ssu re
nun.

337
61*9
696
988
1000
990

£
£
+
+
i
£

*The p r e s s u r e s fo u n d f o r h y d ro g en f l u o r i d e from th e ta n k a re
398 i 3
0°G and 66U — 5
®t 15>°C.

5
10
5
5
5
5

23

1000

P re ssu re
Oram, o f
Hg)

500

0

$0
Mole P e r c e n t H ydrogen F lu o r id e

F ig u r e 5>. V apor p r e s s u r e - c o m p o s itio n diagram s f o r brom ine
p e n ta f lu o r id e - h y d r o g e n f l u o r i d e s o l u t i o n s a t 0 ° , 15° and
25>°C. E r r a t i c r e s u l t s o b ta in e d a t 2£°C made i t n e c e s s a r y
t o show o n ly t h e m o st p r o b a b le a r e a f o r th e c u r v e .

100

2h

TABLE I I I
THE VAPOR PRESSURES OF IODINE PENTAFLUORIDE-HIDROQEN FLUORIDE
SOLUTIONS AT I<°C

Mole P e r c e n t
HF

P re ssu re
mm.
Run I
0

+
1

0 .0

21*6 ; $

3 6 .2

H
CJ

1 0 .S

537 - 3

8 2 .6

597 1 3

+1
r—

21* .5

Run I I
13. h

155 - 3

5 9 .1

M*7 : 3

25

700

P re ssu re
Cnm . o f
350

0
0

50
M ole P e r c e n t H ydrogen F lu o r id e

F ig u r e 6 # V apor p r e s s u r e - c o r a p o s itio n diagram f o r io d in e
p e n t a f l u o r i d e - h y d r o gen f l u o r i d e s o l u t i o n s a t 15 °C .

100

26

TABLE IV
THE VAPOR PRESSURES OF CHLORINE TRIFLU GRIDE-HYDROGHK FLUORIDE
SOLUTIONS AT ZERO DEGREES

Mole P e r c e n t
HF

P re ssu re
ram „

o .o

1*1*8 1 3

1 0 .5

562 1 5

3 3 .2

592 - 5

6 9 .0

61*5 i 5

8 6 .0

527 I 5

600

300

o

o

50

100

M ole P e r c e n t H ydrogen F lu o r id e
F ig u r e 7* V apor p r e s s u re - c o m p o s itio n d iag ram f o r c h lo r in e
t r i f l u o r i d e - h y d r o gen f l u o r i d e s o l u t i o n s a t 0 ° C .

28

t h e l i q u i d s t a t e o f t h e h a lo g e n f l u o r i d e s th e m s e lv e s , and b e c a u se o u r
know ledge o f th e l i q u i d s t a t e o f h y d ro g en f l u o r i d e i s q u a l i t a t i v e a t
best .
The d i e l e c t r i c c o n s t a n t s o f th e h a lo g e n f l u o r i d e s a re a p p a r e n tly
a p p r e c i a b l y lo w e r th a n t h a t o f h y d ro g en f l u o r i d e ,

Thompson1

2

h as

fo u n d th e d i e l e c t r i c c o n s ta n t o f l i q u i d io d in e p e n t a f l u o r i d e t o f o llo w
th e r e la tio n
£ * U6.22 - 0 .3 8 8 t

,

t h a t o f B rF6 to f o l l o w t h e r e l a t i o n
€ -

9 .0 2 - 0 .0 1 1 7 t

,

and t h a t o f c h l o r in e t r i f l u o r i d e t o f o llo w t h e r e l a t i o n

i *

U.75U - 0 .0 1 8 7 1

He a l s o fo u n d t h a t t h e d i e l e c t r i c c o n s ta n t o f c h lo r in e t r i f l u o r i d e i n ­
c r e a s e s m a rk e d ly when h y d ro g en f l u o r i d e i s a d d e d .

The d i e l e c t r i c c o n s ta n t

o f h y d ro g e n f l u o r i d e h a s b een fo u n d b y F re d e n h a g e n 28 t o v a r y from 1 7 k .8
a t -73°C t o 8 3 .6 a t 0 ° C ,

T h e re i s some d o u b t as to th e a c c u ra c y o f th e s e

r e s u l t s , h o w ev er.
The above d a t a le a d t o th e c o n c lu s io n t h a t th e h a lo g e n f l u o r i d e s ,
a lth o u g h u n d o u b te d ly somewhat a s s o c i a t e d , a r e l e s s , a s s o c i a t e d th a n
h y d ro g e n f l u o r i d e i n th e l i q u i d s t a t e .

I t i s th e re fo re n o t s u rp ris in g

t h a t t h e s o l u t i o n s show an a p p r e c ia b le p o s i t i v e d e v i a t i o n from R a o u l t 's
la w .

C h lo r in e t r i f l u o r i d e - h y d r o g e n f l u o r i d e m ix tu re s would i n f a c t be

e x p e c te d to show th e g r e a t e s t d e v i a t i o n , and t h i s seems t o b e th e c a s e
when F ig u r e s 5 , 6 and 7 a r e com pared.

The g r e a t d i f f e r e n c e b etw e e n th e

d i e l e c t r i c c o n s ta n ts o f l i q u i d h y d ro g en f l u o r i d e and o f th e h a lo g e n

29

f l u o r i d e s d o es n o t , h o w ev er, e x p la in t h e f a c t t h a t t h e r e i s l e s s d e v i ­
a t i o n a t lo w e r te m p e r a tu r e s .

T h is d e c r e a s in g d e v i a t i o n would seem t o

i n d i c a t e t h a t t h e r e a re a c t u a l l y two e f f e c t s s u p e rim p o se d .
R e c e n tly D. F . S m ith 24 h a s shown b y means o f s p e c tr o s c o p ic s t u d i e s
o f m ix tu r e s o f c tilo r in e t r i f l u o r i d e and h y d ro g en f l u o r i d e i n th e v a p o r
s t a t e t h a t t h e com plex
F
F -C l . . . F-H
F
i s fo rm ed t o a v e ry s m a ll d e g r e e .

The e q u ilib r iu m c o n s ta n t i s

and t h e h e a t o f f o r m a tio n i s - 3 ,9 2 k c a l . p e r m o le .
A lth o u g h S m ith was n o t a b le t o f i n d any e v id e n c e f o r i t , i t i s a l s o
p o s s i b l e t h a t h y d ro g e n b o n d in g m ig h t o c c u r a t lo w er te m p e r a tu r e s and i n
th e l i q u i d .

I f t h i s w ere th e c a s e , th e d e v i a t i o n s n o te d w ould be th e

r e s u l t o f t h e i n t e r a c t i o n o f two e f f e c t s :

t h e n e g a tiv e d e v i a t i o n c a u se d

b y com plex fo rm a tio n o r h y d ro g en b o n d in g , and th e p o s i t i v e d e v ia ti o n
c a u s e d b y th e v e r y d i f f e r e n t in te r m o le c u l a r atm o sp h e re s o f th e h a lo g e n
f l u o r i d e s and h y d ro g en f l u o r i d e , th e fo rm er becom ing i n c r e a s i n g l y im­
p o r t a n t a t lo w er t e m p e r a t u r e s .
A n o th er p o s s i b l e c a u se o f th e phenomena n o te d c o u ld be t h a t th e
a s s o c i a t i o n o f h y d ro g en f l u o r i d e i s b ro k e n down t o some e x t e n t b y th e
p r e s e n c e o f h a lo g e n f l u o r i d e s .

T h is w ould i n c r e a s e th e v a p o r p r e s s u r e

o f t h e h y d ro g e n f l u o r i d e above th e s o l u t i o n .

I t i s a ls o q u i t e p o s s ib l e

30

t h a t su ch a n e f f e c t c o u ld d e c r e a s e w ith d e c r e a s in g te m p e ra tu re a s i s
n o te d i n F ig u r e 5 .

A c tu a lly b o th o f t h e p r o c e s s e s m en tio n ed above a re

p r o b a b ly p r e s e n t i n th e s o l u t i o n s t o some d e g r e e .

V CRXOSCOFIC STUDIES OF THE HALOGEN FLUORIDES AND THEIR
HYDROGEN FLUORIDE SOLUTIONS
A . T h e o r e t i c a l A s p e c ts 3 6 >a 9
C ry o s c o p ic S tu d ie s o f P u re M a te r i a l s
T he p r in c ip & £ v a r i a b l e s w h ich in f lu e n c e th e s t a t e o f a p u re m a t e r i a l
a r e te m p e r a tu r e and p r e s s u r e .

When a p u re c r y s t a l l i n e s o l i d i s h e a te d

u n d e r i t s own v a p o r p r e s s u r e a te m p e r a tu re i s re a c h e d a t w hich th e s o l i d
s u d d e n ly l i q u i f i e s .
e q u ilib riu m .

A t t h i s p o i n t th e l i q u i d , s o l i d , and v ap o r a re i n

As i s o b v io u s , th e r e i s one more p h a se p r e s e n t a t t h i s

p a r t i c u l a r p o i n t , w hich i s known a s th e t r i p l e p o i n t , and t h e r e f o r e th e
sy stem becom es i n v a r i a n t .
I n a c t u a l p r a c t i c e i t i s g e n e r a l l y fo u n d t h a t th e te m p e r a tu re a t
w hich t h e t r a n s i t i o n o c c u r s i s o n ly s l i g h t l y d e p e n d e n t upon th e p r e s s u r e .
F o r m o st p u r p o s e s t h e te m p e r a tu re a t w hich t h e t r a n s i t i o n o c c u rs i s
d e te rm in e d a t a tm o s p h e ric p r e s s u r e .

T h is te m p e r a tu re i s known as th e

f re e z in g p o in t o f th e s u b s ta n c e .
S in c e i t i s r a r e l y i f e v e r p o s s i b l e t o o b ta i n a s u b s ta n c e w hich i s
a b s o l u t e l y p u r e t h e f r e e z i n g p o i n t w hich i s m easu red s h o u ld , i f p o s s i b l e ,
b e c o r r e c t e d i n some m anner f o r th e e f f e c t o f d is s o lv e d i m p u r i t i e s .

The

e f f e c t o f a s o l u t e upon t h e f r e e z i n g p o i n t o f a p u re s u b s ta n c e i s g iv e n
i n t h e f o llo w in g e q u a tio n

32

w here

i s t h e f r e e z i n g p o i n t lo w e r in g , R i s th e m o la r gas c o n s t a n t ,

T0 i s t h e f r e e z i n g p o i n t o f th e p u r e s o lv e n t and Ns i s th e m ole f r a c t i o n
o f s o lu te .
T h is c an b e s i m p l i f i e d to
Z1T
f

= R T0 m
t f X (lOOO/jyi-J

ATj

*

or
K^m

w here K^ i s d e f in e d b y th e e q u a tio n
Kf

-

R To________
Lf X 10O0/tix

i s t h e m o le c u la r w e ig h t o f th e s o l v e n t , and m i s th e m o l a l i t y .
A t y p i c a l c o o lin g c u rv e f o r a compound c o n ta in in g a s m a ll amount o f
d i s s o lv e d im p u r ity i s g iv e n i n F ig u r e 8 .

As th e te m p e ra tu re o f th e

sam ple i s re d u c e d t h e p l o t o f te m p e r a tu re v e r s u s tim e re s e m b le s c u rv e AB.
A t B t h e sam ple h a s s u p e rc o o le d and j u s t begun t o c r y s t a l l i z e .

The

p r o c e s s o f c r y s t a l l i z a t i o n r e l e a s e s h e a t so t h a t t h e te m p e r a tu re s u d d e n ly
r is e s to C.

C o n tin u e d c o o lin g c a u s e s th e c r y s t a l l i z a t i o n o f more s o l i d ,

th e te m p e r a tu r e f o llo w in g a lo n g th e cu rv e CJ5.

T h is o c c u rs b e c a u se th e

s o l i d i s e s s e n t i a l l y p u r e s o l v e n t th u s c a u s in g th e s o lu t e t o c o n c e n tr a te
i n th e l i q u i d p h a s e and lo w e r i t s f r e e z i n g p o i n t .
i s fro z e n .

At E th e e n t i r e sam ple

An e x t r a p o l a t i o n o f c u rv e CDE t o A g iv e s th e tim e and te m p e r­

a t u r e a t w h ich f u s i o n w ould have o c c u r re d w ith o u t s u p e r c o o lin g .

A t tim e

T l/s j t h e sam p le w i l l b e h a l f f r o z e n and th e c o n c e n tr a t io n o f im p u r ity
w i l l b e x / 2 , i f t h e r a t e o f c o o lin g i s c o n s t a n t .

At t h i s p o i n t th e s o l u t e

6)*-*

33

T e m p e ratu re

x /2
Time

F ig u r e 8 . T y p ic a l c o o lin g c u rv e f o r a s o lv e n t c o n ta in in g a
s m a ll amount o f s o l u t e .

3h

c o n c e n t r a t i o n w i l l be d o u b le t h a t a t p o i n t A.

I t c an be s e e n from th e

re la tio n
ATf *
t h a t t h e f r e e z i n g p o i n t d e p r e s s i o n a t D would be d o u b le t h a t a t A, so
th a t
T0 - Tf - 1 /2 1 T 0 - T y a) .
The t r u e f r e e z i n g p o i n t T 0 may t h e r e f o r e be d e te rm in e d from t h e c o o lin g
c u rv e o f a sa m p le c o n t a i n i n g a s m a ll am ount o f im p u r ity b y th e above
m ethod w hich was d e v e lo p e d b y W hite and m o d ifie d b y W itsc h o n k e .40
Two-Component L iq u id - S o lid P h ase - E q u ilib r ia
The same g e n e r a l c o n s i d e r a t i o n s m en tio n ed i n th e p r e v io u s s e c t i o n
w i l l h o ld i n a d i s c u s s i o n o f th e p h a s e e q u i l i b r i a o f tw o-com ponent
s y s te m s .

I t i s o b v io u s from th e p r e c e d in g d i s c u s s io n t h a t th e p re s e n c e

o f a s u b s ta n c e o t h e r t h a n th e s o lv e n t w i l l in tr o d u c e a t h i r d v a r i a b l e ,
n a m ely , c o n c e n t r a t i o n .

As d is c u s s e d i n th e p r e v io u s s e c t io n t h e f r e e z i n g

p o i n t o f t h e system w i l l be ta k e n a s th e p o i n t a t Tdiich th e l i q u i d - s o l i d
t r a n s i t i o n o c c u rs u n d e r a p r e s s u r e o f one a tm o sp h e re .
The s im p le s t ty p e o f tw o-com ponent l i q u i d - s o l i d system i s one i n
w hich th e com ponents do n o t r e a c t t o form a n o th e r compound.
sy stem i s i l l u s t r a t e d i n F ig u r e 9 .

Such a

The f r e e z i n g p o i n t s o f th e v a r io u s

m ix tu r e s o f two s u c h com ponents w ould f a l l a lo n g th e c u rv e CDE.
f r e e z i n g p o i n t c u r v e s o f A i n B , and B i n A, i n t e r s e c t a t D.

The

When a

m ix tu re o f any c o m p o s itio n b etw een A and x * , o r x* and B , i s c o o l e d , th e
s o l i d p h a s e w h ich s e p a r a t e s f i r s t i s p u re A o r p u re B , r e s p e c t i v e l y .

35

*

b

A

x

U)

T e m p e ra tu re

lb )

x

A

B

B

A
id )

(c)

—
C o m p o sitio n
F ig u r e 9 .

B

Some t y p i c a l p h a s e d iag ram s f o r two com ponent s y s te m s .

36

A t x 1, h o w e v e r, b o th s o l i d s c r y s t a l l i z e o u t o f th e s o l u t i o n a t th e same
tim e .

Thus an a d d i t i o n a l s o l i d p h a se h a s b een in tr o d u c e d and th e system

becom es i n v a r i a n t .
A t y p i c a l c o o lin g c u r v e , su c h as w ould be o b ta in e d when a s o l u t i o n
o f c o m p o s itio n x i s c o o le d , i s i l l u s t r a t e d i n F ig u re 1 0 .

The e x p la n a tio n

o f t h i s c u rv e i s i d e n t i c a l w ith t h a t g iv e n f o r F ig u re 9 e x c e p t t h a t a
e u te c tic h a l t o ccu rs j u s t p r io r to t o t a l s o l i d i f i c a t i o n .

T h is h a l t was

n o t shown i n F ig u r e 8 s in c e i t would be v e r y d i f f i c u l t to o b se rv e w ith
o n ly a v e r y s m a ll am ount o f s o l u t e .
When compound f o r m a tio n o c c u rs th e s i t u a t i o n can become c o n s id e r a b ly
m ore c o m p lic a te d .
i s fo rm e d .

The s im p le s t c a s e i s t h a t i n w hich a s t a b l e compound

I f th e d iag ram shown i n F ig u re 9b i s d iv id e d i n t o two p a r t s

a t x , t h e r e s u l t i n g two s e c t i o n s a r e e a c h i d e n t i c a l w ith F ig u r e 9 a .
A c o n s id e r a b l y m ore c o m p lic a te d s i t u a t i o n a r i s e s when t h e compound
fo rm ed i s u n s t a b l e a s i l l u s t r a t e d i n F ig u r e 9 c .

I n t h i s c a s e th e f r e e z i n g

p o i n t and c o m p o s itio n o f t h e compound form ed ca n o n ly be o b ta in e d by
e x tr a p o la tio n ,a s i l l u s t r a t e d .

A c o o lin g c u rv e f o r s u c h a s y s te m , o f

c o m p o s itio n x , d i f f e r s from t h a t shown i n F ig u re 10 o n ly i n t h a t th e f i r s t
t r a n s i t i o n may b e q u i t e i n d e f i n i t e .
The sy ste m s d e s c r ib e d above a r e a l l ones i n w hich t h e com ponents a re
c o m p le te ly m i s c i b l e i n t h e l i q u i d s t a t e , and i n w hich th e o n ly s o l i d s
w h ich e p p e a r a t p o i n t s o t h e r th a n t h e e u t e c t i c p o i n t a re p u re com ponents
o r com pounds.

O th e r sy ste m s w hich m ig h t be in c lu d e d i n t h i s g e n e r a l

group w ould b e c o m b in a tio n s o f t h e o c c u r re n c e s m en tio n ed a b o v e .

37

T e m p eratu re

Time
F ig u r e 1 0 . T y p ic a l c o o lin g c u rv e f o r a sam ple o f a tw o
com ponent sy stem w ith no compound f o r m a tio n .

38

O th e r ty p e s o f l i q u i d - s o l i d p h a s e e q u i l i b r i a w hich cars o c c u r a re
o n es i n w h ich th e com ponents form m ixed c r y s t a l s , an u n b ro k e n s e r i e s o f
s o l i d s o l u t i o n s , o r s o l i d s o l u t i o n s w ith p a r t i a l m i s c i b i l i t y .

A d e ta ile d

d i s c u s s i o n o f t h e s e o t h e r s i t u a t i o n s w i l l be o m itte d h e r e e x c e p t f o r th e
c a s e o f s o l i d s o l u t i o n f o r m a tio n w ith p a r t i a l m i s c i b i l i t y i n th e s o l i d
phase.

I n t h i s c a s e , a s i l l u s t r a t e d i n F ig u re 9 d , s o l i d A c a n d is s o lv e

a g iv e n amount o f s o l i d B , and s o l i d B c a n d is s o lv e a g iv e n amount o f
s o l i d A.

I f th e l i m i t s o f s o l u b i l i t y a r e ex ceeded two s o l i d p h a s e s a re

fo rm ed and i t i s th u s p o s s i b l e to have one l i q u i d p h a se and two s o l i d
p h a s e s , w hich c a n be s o l i d s o l u t i o n s o r p u re com pounds, e x i s t i n g a t th e
same t im e .

When t h i s o c c u rs th e sy stem becomes i n v a r i a n t and a t r a n s i ­

ti o n , o r a e u te c tic p o in t, i s p o s s ib le .

F ig u r e 9d shows su ch a system

w ith a e u t e c t i c p o i n t .
®* A p p a ra tu s and M ethod
The F r e e z in g P o i n t C e ll
The c e l l , w hich i s i l l u s t r a t e d i n F ig u re 11 and i n P l a t e It, was u se d
f o r t h e d e te r m in a tio n o f t h e f r e e z i n g p o i n t s o f th e hyd ro g en f l u o r i d e
s o l u t i o n s , and o f th e p u re h a lo g e n f l u o r i d e s .

I t was c o n s tr u c te d e n t i r e l y

o f f l u o r o t h e n e and T e f l o n , t h e th erm o c o u p le b e in g th e o n ly m e t a l l i c p a r t
o f th e c e l l .

The c e l l c o n s i s t s o f a f lu o r o th e n e tu b e w ith a m achined

fe m a le s t a n d a r d - t a p e r to p i n t o w hich i s i n s e r t e d a T e flo n p l u g .

The

th e rm o c o u p le l e a d s a re wound aro u n d a tu b e a tta c h e d to th e p lu g ; g ro o v es
f o r th e w ir e were m a ch in ed a lo n g th e t u b e .

The p lu n g e r i t s e l f w hich

39

o p e r a t e s th r o u g h a h o le i n th e tu b e and p l u g , c o n s i s t s o f a f lu o r o th e n e
c y l i n d e r m a c h in e d on t h e o u t s id e to re se m b le a h e l i c a l g e a r .
F o r m o st o f t h e s e m easu rem en ts v ig o ro u s and s a t i s f a c t o r y s t i r r i n g
was o b ta in e d b y u s in g a r e c i p r o c a l s t i r r i n g a c t i o n w ith a s tr o k e o f
a b o u t one and o n e—h a l f in c h e s .

I n th e d e te r m in a tio n o f th e f r e e z i n g

p o i n t o f p u re i o d i n e p e n t a f l u o r i d e , h o w e v e r, c i r c u l a r s t i r r i n g was u se d
f o r some o f th e m e a s u re m e n ts .
The c e l l a s d e s c r ib e d above was n o t a i r - t i g h t .

To p r e v e n t a i r and

v a p o rs from b e in g pumped i n t o and o u t o f th e tu b e by th e a c t i o n o f th e
r e c i p r o c a l s t i r r e r th e c e l l was f i t t e d w ith a hood w hich was f a b r i c a t e d
from t h i n s h e e t f l u o r o t h e n e .

The hood was t i g h t l y s e a le d aro u n d th e

tu b e and t h e p lu n g e r arm , and th e s e a l a t th e p lu n g e r arm was l u b r i c a t e d
■#
w ith F lu o r o lu b e o i l t o p e r m it f r e e a c t i o n th ro u g h th e h o o d . When th e
p lu n g e r was i n o p e r a t i o n th e s i d e s o f th e hood eaqpanded and c o n tr a c te d
b u t d id n o t a llo w v a p o r t o e n t e r o r le a v e th e e n c lo s e d s y s te m .
I n a c t u a l o p e r a t i o n th e c e l l was e n c lo s e d i n a g l a s s a i r - j a c k e t .
The f r e e z i n g p o i n t assem b ly p lu s th e a i r j a c k e t was i n s e r t e d i n t o a o n e l i t e r Dewar f l a s k f i l l e d w ith a p p r o p r ia te c o o l a n t .

A c l e a r Dewar f l a s k

w rapped w ith t r a n s p a r e n t S c o tc h ta p e was u s e d t o o b s e rv e w h e th e r o r n o t
t h e r e was any i m m i s c i b i l i t y i n th e l i q u i d p h a s e .

Som etimes an i n t e r ­

m e d ia te b a th o f t r ic h lo r o f lu o r o m e th a n e was u se d i n s t e a d o f th e a i r j a c k e t .
W h eth er an i n t e r m e d i a t e b a t h was u s e d , and w h eth er Dry I c e - a c e to n e o r
l i q u i d n i t r o g e n w ere u se d a s c o o l a n t s , depended upon th e r a t e o f c o o lin g

* " F lu o ro lu b e 5M was o b ta in e d from th e H ooker E le c tr o c h e m ic a l C o .,
b u f f a l o , N. Y.

hO

d e s ire d .

The r a t e o f c o o lin g was a l s o c o n t r o l l e d t o some e x te n t by th e

u s e o f a i r j a c k e t s o f v a r io u s s i z e s .
T h is c e l l , when u s e d w ith r e c i p r o c a l s t i r r i n g , was q u ite s a t i s f a c t o r y
f o r m o st p u r p o s e s .

When t h e f r e e z i n g p o i n t s o f th e p o re l i q u i d s were

d e te rm in e d , h o w e v e r, i t was fo u n d t h a t th e s e l i q u i d s f r o z e on th e s id e s
o f t h e tu b e and jammed t h e s t i r r e r .

S in c e i t i s im p o rta n t to know when

t h e l i q u i d i s c o m p le te ly f r o z e n i n o r d e r to d e te rm in e th e d e g re e o f
i m p u r i t y , t h i s i s a s e r i o u s o b j e c t i o n t o th e u s e o f th e r e c i p r o c a l s t i r r e r .
The u s e o f v ig o ro u s c i r c u l a r s t i r r i n g f o r m easurem ents o f th e f r e e z i n g
p o i n t o f p u re io d in e p e n t a f l u o r i d e p ro v e d to b e somewhat more s a t i s f a c t o r y ,
and some s a t i s f a c t o r y ru n s were o b ta in e d w ith r e c i p r o c a l s t i r r i n g fo llo w e d
b y m anual s h a k in g a f t e r th e p lu n g e r h ad jammed.
W ith p u r e b ro m in e p e n t a f l u o r i d e th e r e c i p r o c a l s t i r r e r was in a d e q u a te
s in c e th e s t i r r e r f r o z e i n when o n ly ab o u t 20 p e r c e n t o f th e m a t e r i a l was
fro z e n .

A ro u g h d e te r m in a tio n o f th e p u r i t y o f brom ine p e n t a f l u o r i d e

was o b ta in e d u s in g a d i f f e r e n t ty p e o f c e l l i l l u s t r a t e d i n F ig u re 12 .
T h is c e l l was c o m p le te ly s e a l e d and s t i r r i n g was acco m p lish e d by v e ry
v ig o ro u s s h a k in g o f t h e e n t i r e c e l l by m eans o f a s in g l e - c y l i n d e r r e c i p r o c a l - a c t i o n a i r m o to r.

T h is a p p a r a t u s , when u sed as d e s c r i b e d , d id n o t

p e r m it th e u se o f a n a i r j a c k e t b e tw e e n th e c e l l and th e c o o lin g medium
and th u s p r e s e n t e d a s e r i o u s s a f e t y h a z a r d .

T h is m eth o d , how ever, c o u ld

p r o b a b ly b e m o d ifie d t o p e r m it th e u s e o f an a i r j a c k e t and u n d e r su ch
c o n d itio n s m ig h t a ls o p ro v e u s e f u l f o r c ry o s c o p ic s tu d i e s o f s o l u t i o n s
w ith h ig h v a p o r p r e s s u r e s su c h a s c h l o r i n e t r i f l u o r i d e - h y d r o g e n f l u o r i d e
m ix tu re s .

hi

rid

F ig u r e 11* The f r e e z i n g p o i n t c e l l s A , th erm o c o u p le l e a d s ;
B , h o o d ; C , aluminum c o l l a r ; D, f lu o r o th e n e p lu g ; E , a i r j a c k e t ; F , f lu o r o th e n e tu b e ; G, th erm o c o u p le tu b e ; H, f lu o r o ­
th e n e p l u n g e r ; I , Dewar f l a s k ; J , c o o la n t*

)\2

lT S / h v //f x &7\

F ig u r e 12* The f r e e z i n g p o i n t c e l l u s e d w ith p u re brom ine
p e n t a f l u o r i d e s A, t a p e r e d T e f lo n p lu g s ; B , b r a s s cap*

^3

An a tte m p t was made t o d is c o v e r w h eth er t h e r e w ere any s o l i d s t a t e
t r a n s i t i o n s i n io d in e p e n t a f l u o r i d e i n th e r e g io n b etw een i t s f r e e z i n g
p o i n t ^ +9.^°C ) and -2 0 C .

F o r t h i s p u rp o se a sim p le a p p a r a tu s c o n s i s t ­

i n g o f a f lu o r o t h e n e tu b e w ith a s ta n d a r d t a p e r t o p , p lu s a th erm o co u p le
s e a l e d th ro u g h a f lu o r o th e n e p l u g , was u s e d .

A slo w r a t e o f c o o lin g was

a c h ie v e d b y u se o f a l a r g e a i r j a c k e t and a c o o la n t m ix tu re o f i c e and
w a te r t o w h ich a lc o h o l was added a t a s te a d y r a t e .
T e m p e ratu re M easurem ent
T herm ocouple c a l i b r a t i o n and c o n s t r u c t i o n .

The th e rm o c o u p le s u sed w ere

p r e p a r e d from a s i n g l e s p o o l e a c h o f number 2h co p p er w ir e and number 2ii
c o n s ta n t a n w ire o b ta in e d from t h e L eeds and N o rth ro p com pany.

The ju n c ­

t i o n s w ere s i l v e r s o l d e r e d .
The th e rm o c o u p le s w ere c a l i b r a t e d a t t h r e e te m p e r a tu re s w it h in th e
ra n g e o f f r e e z i n g p o i n t m easu rem ents made and w ere exposed t o io d in e
p e n ta flu o rid e b e fo re c a lib r a tio n .

C a l i b r a t i o n p o i n t s a t - 6 3 . £°C and a t

-3 8 .8 S °C w ere o b ta in e d by u s in g th e r e c i p r o c a l - a c t i o n f r e e z i n g p o i n t c e l l
^ F ig u re 11) w ith p u r i f i e d c h lo ro fo rm and w ith m e rc u ry , r e s p e c t i v e l y .
F o r t h e m e rc u ry c a l i b r a t i o n p o i n t t h e p lu n g e r was removed and a
s m a ll g l a s s tu b e i n s e r t e d .
a g ita tio n .

A ir was b u b b le d th ro u g h t h i s tu b e to p ro v id e

The th e rm o c o u p le i t s e l f was c o a te d w ith a t h i n l a y e r o f f lu o r o ­

th e n e t o p r e v e n t a m a lg a m a tio n .

A t h i r d c a l i b r a t i o n p o i n t was o b ta in e d

a t -7 8 .3 9 °C b y u s i n g an e q u ilib r iu m m ix tu re o f c ru sh e d Dry Ic e and carb o n
d io x id e v a p o r .
© te r

To o b t a i n t h e l a t t e r p o i n t a p la tin u m r e s i s t a n c e therm om -

w h ich had b e e n c a l i b r a t e d by th e B u reau o f S ta n d a rd s was u s e d .

* L eed s and N o rth ro p s e r i a l # 1 0 16073.

hh

Tine th e rm o c o u p le w hich was t o be c a l i b r a t e d was p la c e d around th e r e ­
s i s t a n c e th e rm o m e te r w h ile a tt a c h e d to th e p lu g o f th e f r e e z i n g p o i n t
c e l l and th e e n t i r e a sse m b ly was p la c e d i n a o n e - l i t e r Dewar f l a s k con­
t a i n i n g c ru s h e d D ry I c e ( s e e F ig u re 12;) .

The Dewar was co v e re d w ith a

c o r k and th e m ix tu r e a llo w e d t o come t o e q u i l i b r i u m .

The r e s i s t a n c e

o f t h e p la tin u m r e s i s t a n c e th erm o m eter was m easured by means o f a M u e lle r
B rid g e * w hich was a l s o c a l i b r a t e d by th e B u reau o f S ta n d a r d s .

The B ureau

o f S ta n d a rd s c e r t i f i c a t e i n d i c a t e d t h a t th e r e s i s t a n c e d i f f e r e n c e s co u ld
b e r e a d t o - 0 .0 2 $ on th e M u e lle r B r id g e .

The c o r r e c t te m p e ra tu re was

o b ta in e d from t h e B u reau o f S ta n d a rd s e q u a tio n
Rt * Ro f l

- ^ < .v u - t A o o ) t / 1 0 0 ] .

i s t h e r e s i s t a n c e a t t d e g r e e s C e n tig ra d e and th e v a lu e s f o r th e con­
s ta n ts

and v a r e 0.00392601* and 1.1*919, r e s p e c t i v e l y .

R0 has p r e v io u s ly

b e e n fo u n d t o b e 2 5 .5 0 3 1 o h m s.12
The c a l i b r a t i o n d a t a a re g iv e n i n th e f o llo w in g t a b l e .
TABLE V
CALIBRATION DATA FOR THE COPPER-CONSTANTAN THERMOCOUPLE

Compound

A E
( m ic r o v o lts )

o ^
T* C

T«°C

A T *°C

CHCla

llt2 2

- 6 3 .7 - .02

- 6 3 .5

-tO.2

Hg
co2

2251)

- 3 8 .8 0 1 .02

- 3 8 .8 5

-0.05

2726

-7 8 .7 8 1 .02

-7 8 .3 9

+0.39

* L eed s and N o r th r u p , ty p e G - l , s e r i a l #10111*19.

U5

A E i s th e d i f f e r e n c e b etw een th e p o t e n t i a l o f th e c o ld ju n c tio n a t
0°C and t h a t o f t h e th e rm o c o u p le t o be c a l i b r a t e d , T *° i s th e te m p e ra ­
t u r e o b ta in e d from th e s ta n d a r d th e rm o c o u p le t a b l e s , 4° and Tw i s th e
te m p e r a tu re o f t h e f r e e z i n g p o i n t s o f c h lo ro fo rm and m e r c u ry ,41 o r th e
te m p e r a tu r e o f t h e c ru sh e d Dry I c e m i x t u r e , r e a d from th e r e s i s t a n c e
th e rm o m e te r.

The e x p e r im e n ta l e r r o r s shown a r e th e e r r o r s i n r e a d in g

t h e c o o lin g c u r v e s .

I t s h o u ld be n o te d t h a t th e above p ro c e d u re a c t u a l l y

c a l i b r a t e d th e e n t i r e sy stem f o r th e d e te r m in a tio n o f

AE.

The c a l i ­

b r a t i o n c u rv e i s p l o t t e d i n F ig u r e 1 3 ,
The m ethod f o r o b t a i n i n g

A E f o r a l l th e c ry o s c o p ic work i s g iv e n

b e lo w .
•

The i c e - p o i n t r e f e r e n c e . The m easurem ent o f te m p e r a tu re by means o f a
th e rm o c o u p le r e q u i r e s a s te a d y and a c c u r a t e l y known r e f e r e n c e te m p e ra tu re
s in c e t h e p o t e n t i a l m easu red ( A E) depends upon th e te m p e ra tu re o f th e
two j u n c t i o n s .

The i c e p o i n t i s th e m ost c o n v e n ie n t r e f e r e n c e p o i n t f o r

t h i s ty p e o f w o rk .
The i c e p o i n t was o b ta in e d by th e u s e o f a m o d if i c a tio n o f a d e v ic e
d e s c r ib e d b y W hite , 43

The g la s s tu b e i l l u s t r a t e d i n F ig u re 15 was f i l l e d

w ith c r u s h e d i c e p r e p a r e d from w a te r wliich was d i s t i l l e d and th e n d e­
io n iz e d .

T h is i c e was th e n w ashed b y p a s s in g p u re c h i l l e d w ater th ro u g h

th e s i d e tu b e s and th e n was l e f t p a r t i a l l y f i l l e d w ith w a te r and i c e .
The th e rm o c o u p le was p la c e d i n t o th e i c e m ix tu re th ro u g h th e c e n t e r tu b e
and th e e n t i r e assem b ly was p la c e d i n a Dewar f l a s k c o n ta in in g c ru sh e d
ic e .

T h is d e v ic e h o ld s t h e te m p e r a tu re s te a d y a t 0 .0 0 0 0 1 ,0001°C f o r

ho

-

0.2

T°C
c o rrn .

O

-1*0

-8 0

T e m p e ratu re

F ig u r e 1 3 . T herm ocouple c a l i b r a t i o n c u rv e f o r c o r r e c t i o n s t o
b e a p p lie d t o te m p e r a tu r e s o b ta in e d from s ta n d a r d th e rm o c o u p le
ta b le s .

h7

F ig u r e 1 4 , D ia g ra n o f th e a p p a r a tu s f o r o b ta in i n g t h e
c a l i b r a t i o n p o i n t a t -7 8 .3 9 °C s A , t h e p la tin u m r e s i s t a n c e
th e rm o m e te r; B , t h e t a p e r e d f lu o r o th e n e p lu g and th erm o ­
c o u p le from th e f r e e z i n g p o in t c e l l .

hb

up t o 2h h o u rs a c c o r d in g t o W h ite .

T h is a c c u ra c y i s , o f c o u r s e , f a r

g r e a t e r th a n t h a t r e q u i r e d f o r th e s e m e a su re m e n ts.

F ig u r e 1 5 .
The d e te r m in a tio n o f

The i c e - p o i n t tu b e s T i s a th e rm o c o u p le .
A E.

The d i f f e r e n c e i n p o t e n t i a l ( A E) b etw een

t h e th e rm o c o u p le i n t h e f r e e z i n g p o i n t c e l l and th e r e f e r e n c e th erm o c o u p le
was

d e te rm in e d b y u s e o f a Brown R e c o rd in g P o te n tio m e te r and a L eeds and

N o rth ru p ty p e K-2 P o t e n t i o m e te r .

A sim p le d e v ic e was u s e d t o p r o v id e a

s te a d y b u c k in g p o t e n t i a l w hich c o u ld b e v a r i e d a t w i l l ( s e e F ig u re 1 6 ) .
W ith t h i s d e v ic e i t was p o s s i b l e t o o b t a i n an o u tp u t p o t e n t i a l o f s u c h a
m a g n itu d e t h a t t h e r e c o r d in g p o te n ti o m e t e r , when u se d i n c o n ju n c tio n w ith
a L eeds and f lo rth ru p D. C . a m p l i f i e r , had a s e n s i t i v i t y o f o n e - q u a r te r t o
o n e - h a l f d e g re e p e r i n c h .

The z e r o l i n e on t h e r e c o r d in g p o te n tio m e te r

i s t h u s e q u a l t o t h e b u c k in g p o t e n t i a l and

A E i s o b ta in e d d i r e c t l y by

a d d in g t h e b u c k in g p o t e n t i a l t o th e p o t e n t i a l r e c o r d e d .

The b u c k in g

U9

C o ld
f u n c tio n

C e ll
th e rm o c o u p le

Type K-2
p o te n tio m e te r

Brown R e c o rd in g
P o te n tio m e te r

Leeds & flo rth ru p
D #C . A m p lifie r

F ig u re 1 6 . The a p p a r a tu s f o r th e d e te r m in a tio n o f te m p e ra tu re
u s in g a th e rm o c o u p le : Rx , s ta n d a r d d ecad e r e s i s t a n c e b o x ; Ra ,
s t u d e n t p o t e n t i o m e t e r ; a known b u c k in g v o lta g e i s ta k e n from
R a.

50

v o lta g e was d e te rm in e d d i r e c t l y w ith th e ty p e K-2 p o te n tio m e te r .

The

b u c k in g v o lta g e was fo u n d t o have a maximum v a r i a t i o n o f p lu s o r m inus
one m ic r o v o lt d u r in g a p e r i o d o f tw e lv e h o u r s .
The ty p e K-2 p o te n tio m e te r was a ls o c o n n e c te d d i r e c t l y a c r o s s th e
th e rm o c o u p le l e a d s so t h a t r e a d in g s c o u ld be ta k e n w h ile th e r e c o r d e r
was o p e r a t i n g .

Im n ie d ia te ly a f t e r th e r e a d in g on th e K-2 p o te n tio m e te r

was r e a d i t was th ro w n o u t o f b a la n c e and th e c o n t a c t c lo s e d f o r an
in s ta n t.

T h is p u t a m ark on th e c h a r t o f th e r e c o r d in g p o te n tio m e te r and

th u s t h e r e a d i n g s o f th e two p o te n tio m e te r s w ere s im u lta n e o u s ly re c o rd e d
on th e same g r a p h .

The ty p e K-2 p o te n tio m e te r th u s s e rv e d as a c a l i b r a t ­

in g d e v ic e f o r t h e r e c o r d i n g p o te n tio m e t e r .
The above s e t up f o r th e r e c o r d in g o f th erm o c o u p le v a lu e s when mak­
in g p h a s e s t u d i e s i s v e r y c o n v e n ie n t as i t p e r m its one to r e c o r d c o o lin g
c u rv e s d i r e c t l y w ith a r e c o r d in g p o te n tio m e te r o v e r any g iv e n te m p e ra tu re
ran g e.
H a n d lin g P ro c e d u re s and P r e p a r a t i o n o f S o lu tio n s
P r e p a ra tio n o f th e s o lu tio n s .

The h a lo g e n f l u o r i d e , th e p u r i f i c a t i o n and

s to r a g e o f w hich h a s b ee n d e s c r ib e d a b o v e , was sip h o n ed d i r e c t l y from th e
s to r a g e c o n t a i n e r ^ P la te 3) i n t o a p r e v i o u s l y w eighed f lu o r o th e n e tu b e f i t ­
t e d w ith a p lu g and a v a l v e . The v a lv e o v e r th e tu b e was th e n c lo s e d and th e
l i n e c le a n e d by e v a c u a tio n and h e a t i n g . The tu b e and v a lv e assem bly was th e n
rem oved and w eighed on a T o rs io n b a la n c e . The assem b ly was th e n p la c e d on
th e m e ta l vacuum l i n e and th e l i q u i d was f r o z e n by u se o f a Dry I c e a c e to n e m i x t u r e .

The v a lv e was th e n opened and hydrogen f l u o r i d e was

51

co n d en sed d i r e c t l y i n t o t h e tu b e from a ta n k c o n n e c te d t o th e l i n e .
The w e ig h in g p ro c e d u re was r e p e a te d as d e s c r ib e d a b o v e .
A f t e r t h e s o l u t i o n was p r e p a re d i t was c h i l l e d t o j u s t above th e
f r e e z i n g p o i n t , t h e p lu g and v a lv e w ere rem oved, and th e s t i r r i n g assem bly
was i n s e r t e d i n t o t h e t u b e .

The amount o f im p u r ity in tro d u c e d b y t h i s

b r i e f e x p o s u re t o th e a tm o sp h ere i s c o n s id e re d t o b e n e g l i g i b l e .
H ydrogen f l u o r i d e .

The f r e e z i n g p o i n t o f th e hydro g en f l u o r i d e o b ta in e d

d i r e c t l y from t h e c y l i n d e r was d e te rm in e d t o b e - 8 2 .9 * 0.1°C by th e
p r o c e d u re i n d i c a t e d a b o v e .

T h is a g r e e s r e a s o n a b ly w e ll w ith p r e v io u s ly

r e c o r d e d v a lu e s o f - 8 3 .3 7 ° C ,37 and - 8 3 .0 7 ° C .i e ^> The hydrogen f l u o r i d e
from t h e c y l i n d e r was th u s assumed to be s u i t a b l e f o r th e s e m easu rem en ts.
I t was n o t p o s s i b l e t o d e te rm in e th e ap p ro x im a te amount o f im p u r ity
p r e s e n t i n t h e h y d ro g e n f l u o r i d e b e c a u se th e s t i r r e r jammed b e f o r e an
a p p r e c ia b le f r a c t i o n o f t h e m a t e r i a l f r o z e o u t , and p o o r c o o lin g c u rv e s
w ere o b t a i n e d .
H ydrogen f lu o r i d e - p o t a s s i u m f l u o r i d e s o l u t i o n s .

The c o o lin g c u rv e s f o r

s e v e r a l h y d ro g e n f lu o r id e - p o ta s s iu m f l u o r i d e s o l u t i o n s were ru n a t h ig h
h y d ro g e n f l u o r i d e c o n c e n t r a t i o n s t o h e lp co m p lete t h e d a ta o f C ad y .44
F o r t h i s p u rp o s e a w eig h ed amount o f p o ta ssiu m b i f l u o r i d e

■K

was p la c e d

i n t h e f lu o r o t h e n e tu b e and a w eighed amount o f hydrogen f l u o r i d e was
added a s d e s c r i b e d a b o v e .

* M erck & C o.

52

C.

D a ta and C a lc u la tio n s

On t h e f o llo w in g p a g e s th e d a t a f o r th e c ry o s c o p ic s t u d i e s a re
p r e s e n t e d i n t a b u l a r and g r a p h ic a l form .
The f r e e z i n g p o i n t s f o r each i n d i v i d u a l s o l u t i o n were d e te rm in e d
from t h e r e c o r d e d c o o lin g c u rv e s (som e i l l u s t r a t i o n s o f w hich a r e g iv en
i n F ig u r e s 1 7 , 18 and 2 1 ) .

The e r r o r i n d i c a t e d f o r each f r e e z i n g p o in t

i s e s tim a te d from t h e p a r t i c u l a r c o o lin g c u rv e in v o lv e d ; h o w ev er, none
o f t h e v a lu e s a r e b e t t e r th a n - 0 .02°C as t h i s i s th e ap p ro x im a te l i m i t
o f th e a c c u r a c y o f th e th e rm o c o u p le c a l i b r a t i o n .

V ery l a r g e e r r o r s f o r

c e r t a i n p o i n t s i n d i c a t e , i n g e n e r a l , t h a t t h e s lo p e o f th e f r e e z i n g
p o i n t c u rv e was v e ry s t e e p .
O th e r i n f o r m a tio n r e g a r d in g th e f o llo w in g t a b l e s i s p r e s e n te d e i t h e r
a s a f o o tn o t e t o t h e t a b l e i n q u e s ti o n , o r i n th e t e x t im m e d ia te ly
p r e c e d in g t h e t a b l e .

53

table

VI

CRYOSCOPIC DATA FOR IODINE PENTAFLUORIDE-HYDROGEN FLUORINE SOLUTIONS*

W eight
HF tg m .)
0 .2 6
0 .2 6
0 .5 2
1.1*0
1 .0 0
3 .3 7
6 .9 0
9 .7 5
1 1 .0 6
1 2 .6 7
1 6 .5 5
2 2 .1 5
2 3 .7 0
2 6 .1 0
2 6 .2 6
3 2 .1 0
3 1 .5 5
2 8 .8 5
1*0.8

la .17
1*2.28
1*2.35
1*6.55

W eig h t
IF 6 lg m .)

M ole P e r c e n t
HF

11*0.8
1 3 7 .7
2 3 1 .3
2 0 3 .1
1 2 7 .6
1 5 3 .0
1 3 8 .8
1 1 8 .9
1 1 8 .6
1 1 5 .9
1 0 8 .5
101*.2
8 5 .2
9 3 .7
61*.5
5 9 .5
51*.8
31*. 88
31*.1*3
2 1 .1 8
1 7 .0 0
6 .9 0
3 .0 0

1 *99
2 .0 6
l* .5 l
7 .1 0
6 .0 0
1 9 .6
3 5 .6
1*7.7
5 0 .6 7
5 5 .1 9
6 2 .6 7
7 0 .1 9
7 5 .5
7 5 .7
8 1 .2
6 5 .6 9
66.1*7
9 0 .1 9
9 2 .9
9 5 .5 9
9 6 .5 2
9 8 .5
9 9 .5

F r e e z in g
P o in t°C
6 .11
8 .0 0
6 .7 0
1*.1*6
1*.1*6
-0.21*
- 6 .0 0
- 1 0 .3 6
- 1 0 .0 6
- 1 2 .2 0
- 1 5 .1 0
- 1 7 .5
- 2 0 .5
-20.1*
- 2 3 .1 5
- 2 5 .9
- 2 6 .7
- 3 1 .2
- 5 3 .1
-1*1*.8
- 5 2 .0
- 7 2 .9
-83.1*9

! o .02
1 0 .0 3
1 0 .0 2
1 0 .0 6
1 0 .0 6
1 0 .0 6
i 0 .0 6
1 0 .0 2
1 0 .0 6
1 0 .0 2
1 0 .0 6
- 0 .3
1 0 .3
i 0 .1
± 0 .0 6
1 0 .3
1 0 .3
1 0 .3
- 0 .5
il.O
i 0 .3
1 0 .1 *
1 0 .0 6

E u t e c ti c
P o in t°C
MMW

--------- ------83.1***
----8 0 t o - 8 ^
— -

—
- 8 3 .5 5
-

—

-t- 3 . :>'
-83.1*9
-83.1*9
-83.1*9
-83.1*3
-83.1*9

*The e u t e c t i c p o i n t i s a t 9 9 .5 m ole p e r c e n t h y d ro g en f l u o r i d e
and -t55M9°C.
The e x p e r im e n ta l e r r o r g iv e n f o r th e f r e e z i n g p o i n t i s
ta k e n a s t h e maximum e r r o r i n r e a d in g ea c h i n d i v i d u a l c o o lin g
c u r v e . T h is e r r o r i n c r e a s e s w ith in c r e a s in g hydrogen f l u o r i d e
c o n c e n t r a t i o n b e c a u s e o f th e i n c r e a s i n g s lo p e o f th e c o o lin g
c u r v e , i n a l l c a s e s th e e r r o r l i s t e d h e r e i s th e same a s , o r
g r e a t e r t h a n , t h e e r r o r i n t h e th e rm o c o u p le c a l i b r a t i o n .
**The e u t e c t i c was re a c h e d i n th e s e c a s e s by m anual s h a k in g a f t e r
th e p lu n g e r had jammed.

15

A

8
o

-10

Time <a r b i t r a r y s c a l e )
F ig u r e 17 * Some r e p r e s e n t a t i v e c o o lin g c u rv e s f o r io d in e p e n t af lu o r id e - h y d r o g e n f l u o r i d e s o l u t i o n s : A, io d in e p e n t a f l u o r i d e
from s to r a g e c o n t a i n e r ; B and C , 1 9 .6 and 5 5 .2 m ole p e r c e n t
h y d ro g e n f l u o r i d e , r e s p e c t i v e l y . The c u r v e s a r e in c o m p le te b e ­
c a u s e s t i r r e r jammed b e f o r e f r e e z i n g was c o m p le te .

55

-80
Time
F ig u r e 1 8 . Some r e p r e s e n t a t i v e c o o lin g c u rv e s f o r io d in e
p e n ta f lu o r id e - h y d r o g e n f l u o r i d e s o l u t i o n s : D , E and F
c o n t a i n 8 1 .2 , 9 0 . 2 , and 9 9 .5 m ole p e r c e n t hydrogen f l u o r i d e
r e s p e c tiv e ly . At th e p o in t in d ic a te d by
th e c o o lin g
b a t h was ch an g ed from Dry X c e -a c e to n e t o l i q u i d n i t r o g e n .

56
10

-9 0
0

So

100

Mole P e r c e n t H ydrogen F lu o r id e
F i g u r e 1 9 , P h a se d iag ram o f th e sy stem io d in e p e n t a f l u o r i d e h y d ro g e n f l u o r i d e „ D e t a i l o f p o r t i o n AB i s g iv e n i n F ig u re 20 #

5?

o.o

}o
10.0

■

-

20.0

£0.0
M ole P e r c e n t H ydrogen F lu o r id e
F ig u r e 2 0 . D e t a i l o f t h e p h ase d iag ram o f th e sy stem io d in e
p e n ta f lu o r id e - h y d r o g e n f l u o r i d e show ing a p o s s i b l e p e r ite c f c ic
p o in t.

56

TABLE V l l

CRY03C0PIC DATA FOR BROMINE PENTAFLUCRlDE-HYDRGGEN FLUORIDE SOLUTIONS

W eig h t
HF(gm.)

W eight
IF e lg m .)

M ole P e r c e n t
HF

0 .2 8

1 0 6 .5

2 .2 5

- 6 2 .2 0 1 0 .0 2

0 .8 2

1 1 6 .6

5 .7 9

- 6 2 .6 9 1 0 .0 7

1 .8 2

1 0 7 .1

1 2 .9

- 6 3 .5 0 1 0 .0 2

2 .51*

1 0 2 .0

1 7 .9

- 6 3 .7 5 i 0 .0 2

3 .3 0

1 1 0 .6

2 0 .7

-61*.08 t 0 .0 3

3 .8 1

9 5 .6

2 5 .8

-61* .1*3 1 0 .0 2

6 .0 5

9 2 .5

3 6 .3

-61*. 96 1 O .03

9 .9 0

8 8 .9

1*9.3

- 6 5 .6 2 1 0 .0 2

1 2 .8 9

7 6 .6

5 9 .5

- 6 6 .1

1 7 .2 9

71*.6

6 7 .0

- 6 6 .7 0 2 0 .0 2

-----

2 7 .5 7

5 3 .1

8 1 .9

- 6 8 . 1*0 1 0 .0 2

-----

3 6 .0 2

3 7 .6

8 9 .3

- 7 2 .7

- O .it

-----

39.U 5

2 7 .9

9 2 .5

- 7 8 .2

! 0 .1*

- 6 5 .6 1

1 3 .1 0

2 2 .0

91*.5

- 81*.5

- 0 .1*

- 8 5 .6 1

1*1*.67

13.1*

9 6 .7

- 81*.98 * 0 .0 3

9 8 .6

-83.91* i 0 .0 3

1*1*.20

5.1*5

F r e e z in g
P o in t °C

E u t e c ti c
P o in t °C
----

-----

-----

! o .l

—

The e u t e c t i c p o i n t i s a t 95-2 m ole p e r c e n t h y d ro g en f l u o r i d e
and -8 5 * 6 l° C .

59

-70

'c

Time
F ig u r e 2 1 . Some t y p i c a l c o o lin g c u r v e s o f b ro m in e p e n t a f l u o r i d e h y d ro g en f l u o r i d e s o l u t i o n s : A, b ro m in e p e n t a f l u o r i d e from s to r a g e
c o n t a i n e r ; B , C , D and B c o n ta in 2 5 * 8 , 8 1 .9 , 9 2 .5 and 9 6 ,7 m ole
p e r c e n t h y d ro g e n f l u o r i d e , r e s p e c t i v e l y . The tim e s c a l e and c o o la n t
u s e d f o r A and B a r e d i f f e r e n t th a n t h o s e f o r C , D and £ ,

60

-6 0
A

-9 0

100

0
M ole P e r c e n t hydrogen F lu o r id e

F ig u r e 2 2 . P h a se diagram o f t h e system brom ine p e n t a f l u o r i d e faydrogen f l u o r i d e . D e t a i l o f t h e p o r t i o n AB i s shown i n
F ig u r e 2 3 .

61

-

60.0

-6 5

0 .0

10

20

M ole P e r c e n t H ydrogen F lu o r id e
F i g u r e 2 3 . D e t a i l o f t h e p h a s e diagram o f th e sy stem io d in e
p e n t a f lu o r id e - h y d r o g e n f l u o r i d e show ing a p o s s ib le t r a n s i t i o n
i n th e s o lid p h a se .

62

The f r e e z i n g p o i n t s o f i o d in e p e n t a f l u o r i d e and brom ine p e n t a f l u o r i d e
w ere c a l c u l a t e d by t h e m ethod o f W itsch o n k e* 0 and a r e t a b u l a t e d i n
T a b le V I I I .

A lso t a b u l a t e d i s th e m e asu red f r e e z i n g p o i n t o f hyd ro g en

f l u o r i d e t a k e n d i r e c t l y from th e c y l i n d e r .

The W itsch o n k e m ethod was n o t

u s e d f o r h y d ro g e n f l u o r i d e b e c a u se th e s t i r r e r jammed b e f o r e an a p p re ­
c i a b l e p e r c e n ta g e o f t h e h y d ro g en f l u o r i d e had f r o z e n .
TABLE V H I
THE FREEZING POINTS OF IODINE PENTAFLUORIDE, BROMINE PENTAFLUORIDE,
AND HYDROGEN FLUORIDE

Compound
I o d in e p e n t a f l u o r i d e

T h is Work
{l .P .°C

“i

9.1*27 i 0 .0 2

B rom ine p e n t a f l u o r i d e

- 6 0 .6 3

- 0 .0 2 6

H ydrogen f l u o r i d e

- 8 2 .9

1 0 .1 -

0 .0 0 8 6
0 .0 2 6

P r e v io u s ly R e p o rte d
F .P ,UC
R e fe re n c e
9 .6
9.1*25
- 6 1 .3

(9 )
U 2)
(7 )

- 8 3 .0 9
-8 3 .3 7

U S b)
137)

m i i s th e m o la l c o n c e n t r a ti o n o f im p u r ity c a l c u l a t e d by t h e
m ethod o f W itsc h o n k e .

Figure

2h*

Cooling

rH

O

o°°‘
E-*

curve

for

pure iodine

p e n ta f lu o r id e ,

63

6b

TABLE IX

CRXOSCOPIC DATA FOR SEVERAL HYDROGEN FHJORIDE-PCTASSlUM
FLUORIDE SOLUTIONS

W eight
HFCgm.)

W eight
KHF2(gni.)

55.75

1 .2 9 9 0

9 9 .3 9

- 8 3 .8 0 1 0 .0 3

U5.37

0 .5 9 0 5

9 9 .6 5

- 8 3 ,3k - 0 .0 3

h 2 .$ l

0.300U

9 9 .8 1

-8 3 .2 2 i O.Oii

F . P . °C

Mole P e r c e n t
HF

CRXOSCOPIC DATA REPORTED BX CADI FOR HXDROGQi FLUORIDE-POTASSIUM
FLUORIDE SOLUTIONS*

M ole P e r c e n t
HF

o_
F .P . C
—

„ 0 -jhs
F .P . C
„

1 0 0 .0 0

-8 3 .7

- 8 3 .0

9 8 .7 5

- 8 5 .2

-81* .5

9 7 .3 2

- 8 6 .9

- 8 6 .2

*The f r e e z i n g p o i n t s r e p o r te d b y Cady were o b ta in e d u s in g an
u n c a l i b r a t e d th e rm o c o u p le . The v a lu e s w h ich he r e p o r te d
( F .F * ° C ) h a v e t h e r e f o r e b e e n c o r r e c te d f o r th erm o co u p le e r r o r
(F . P . ° C ^ t y t a k i n g h i s r e p o r t e d v a lu e f o r th e f r e e z i n g p o i n t
o f h y d ro g e n f l u o r i d e a s a c a l i b r a t i o n p o i n t . I f J o h n s to n fs
d a t a f o r t h e f r e e z i n g p o i n t s o f hydrogen f l u o r i d e a re u se d
no a g re e m e n t i s o b t a i n e d .

-0 3

0V

-61*
T°C

-8 5 -

-8 6

\

—

M ole P e r c e n t H ydrogen F lu o r id e

F igu re 25# D e ta il o f the phase diagram o f the
system hydrogen flu o r id e -p o t as slum flu o r id e :
o determined in t h i s work; ^ determ ined by
Cady.

66

C ry o sc o p ic c o n s ta n ts w ere d e te rm in e d from l a r g e s c a l e p l o t s o f th e
p h a s e d ia g ra m s and by u s e o f th e r e l a t i o n , 36

m

^2

W1

1006 w2
w here

i s t h e c r y o s c o p ic c o n s t a n t , A T ^ th e f r e e z i n g p o in t d e p r e s s io n ,

t h e m o le c u la r w e ig h t o f th e s o l u t e , w2 t h e w e ig h t o f s o lu t e and wA
th e w e ig h t o f s o l v e n t .

A

was d e te rm in e d from t h e s lo p e o f th e

f r e e z i n g p o i n t c u rv e a t i n f i n i t e d i l u t i o n .
H e a ts o f f u s i o n w ere d e te rm in e d by u s e o f th e r e l a t i o n 36
InN , -

w here

"L f

i s th e m o la r h e a t o f f u s i o n ,

ATf
RT»
th e m ole f r a c t i o n o f s o lv e n t

and T0 i s t h e f r e e z i n g p o i n t o f th e p u re m a t e r i a l i n d e g re e s K e lv in .
V a lu es o f t h e s e c o n s ta n ts w ere d e te rm in e d f o r io d in e p e n t a f l u o r i d e ,
b ro m in e p e n t a f l u o r i d e , and h y d ro g en f l u o r i d e and a re t a b u l a t e d i n
T a b le J .

When t h i s m ethod i s u se d f o r o b ta in in g h e a ts o f f u s i o n i t m ust

b e assum ed t h a t s o l i d s o l u t i o n s a re n o t fo rm e d .

67

TABLE X
CRYOSCOPIC CONSTANTS AND HEATS OF FUSION OF BRCMINE PENTAFLUORIDE,
IODINE PENTAFLUORIDE AND HYDROGEN FLUORIDE

Compound

Kf
D eg rees P e r Mole

if
K c a l. P e r Mole

System
S tu d ie d

1 2 .2

2 .6 9

HF i n IF 6

1U.O*

1 .0

HF i n BrFe

HF

1 .5 3

1 .0

BrFe i n HF

HF

1 .1 6

1 .3 2

KF i n HF

BrFe

^ T h is v a lu e i s v e r y d o u b tf u l b eca u se th e sh a p e o f th e f r e e z i n g
p o i n t c u rv e made
d i f f i c u l t to o b ta in .

68

D.

D is c u s s io n o f th e R e s u lts
The P u re M a te r ia l s

The f r e e z i n g p o i n t s o f b rom ine p e n t a f l u o r i d e and io d i n e p e n t a f l u o r i d e
a s d e te rm in e d i n t h i s w ork a re a p p r e c ia b ly lo w e r th a n th o s e r e p o r t e d by
R u ff.

The f r e e z i n g p o i n t f o r i o d in e p e n t a f l u o r i d e i s , h o w ev er, i n e x ­

c e l l e n t a g re em e n t w ith p r e v io u s w ork done i n t h i s l a b o r a t o r y , 13 a lth o u g h
a s l i g h t l y d i f f e r e n t m ethod was u s e d .

I t i s n o t a t a l l s u rp ris in g th a t

th e f r e e z i n g p o i n t s o b ta in e d h e r e d i f f e r from th o s e p r e s e n te d by R u f f ,
s in c e t h e e a r l i e r s t u d i e s were ham pered b y a la c k o f a d e q u a te m a t e r i a l s
f o r t h e p u r i f i c a t i o n and h a n d lin g o f th e h a lo g e n f l u o r i d e s . The d a t a
WE
a r e l i s t e d i n T a b l ^ I ^ a l o n g w ith th e m o la l im p u r ity i n e a c h sam ple as
c a l c u l a t e d b y t h e m ethod o f W itsc h o n k e . 40

The f r e e z i n g p o in ts o b ta in e d

by o t h e r w o rk ers a r e a l s o l i s t e d .

The P h ase D iagram s
The p h a se d iag ram o f t h e io d in e p e n ta f lu o r id e - h y d r o g e n f l u o r i d e s y s ­
tem ^ F ig u re 19) lo o k s v e r y much l i k e t h a t o f a sim p le tw o-com ponent system
w ith a e u t e c t i c p o i n t a t 9 9 .5 p e r c e n t hydrogen f l u o r i d e , e x c e p t t h a t a t
5*0 and a t 1*8 .8 m ole p e r c e n t hydro g en f l u o r i d e t h e r e a re s l i g h t d is c o n tin u tie s .

The d i s c o n t i n u i t y w hich o c c u rs a t 1*8.8 mole p e r c e n t hydrogen

f l u o r i d e , a lth o u g h i t i s v e r y s l i g h t , seems t o be a p e r i t e c t i c p o i n t .
T h is p o i n t i s shown i n t h e d e t a i l o f th e p h ase diagram shown i n F ig u re 2 0 .
The v e r y s m a ll change i n s lo p e a t c o n c e n tr a tio n s j u s t above th e p e r i t e c t i c

69

p o i n t makes i t v e ry d i f f i c u l t t o e x t r a p o l a t e th e c u rv e i n o r d e r to
d e te rm in e th e c o m p o s itio n o f th e compound w hich may be fo rm ed .
The f a c t t h a t t h e r e i s an i n d i c a t i o n o f compound f o r m a tio n below
f i f t y m o le p e r c e n t h y d ro g en f l u o r i d e i s s u r p r i s i n g and an e f f o r t was made
t o d e te r m in e w h e th e r t h e r e was any s o lid - p h a s e t r a n s i t i o n i n io d in e
p e n t a f l u o r i d e a t t h e a p p a r e n t p e r i t e c t i c and a t th e d i s c o n t i n u i t y a t f i v e
m ole p e r c e n t .

The m ethod u s e d , w hich i s d e s c r ib e d a b o v e , was q u i te c r u d e ,

and th e l a c k o f e v id e n c e f o r a s o l i d - s t a t e t r a n s i t i o n by t h a t m ethod does
n o t p ro v e t h a t s o l i d - s t a t e t r a n s i t i o n s do n o t o c c u r .

The c u rv e o b ta in e d

f o r t h e slo w c o o lin g o f io d in e p e n t a f l u o r i d e i s shown i n F ig u re
The p h a s e diagram o f th e brom ine p e n ta f lu o r id e - h y d r o g e n f l u o r i d e
sy stem a l s o a p p e a rs a t f i r s t g la n c e t o b e a s im p le tw o-com ponent system
w ith o u t compound f o r m a tio n .

The e u t e c t i c p o in t i n t h i s c a s e o c c u r s a t

9 9 .2 m ole p e r c e n t h y d ro g en f l u o r i d e .

T h e re i s a p p a r e n tly a v e r y s l i g h t

d i s c o n t i n u i t y a t e i g h t e e n m ole p e r c e n t h y d ro g en f l u o r i d e , h o w ev er, as
ca n be s e e n i n t h e d e t a i l o f th e p h ase diagram i n F ig u re 2 3 .

I t s h o u ld

be n o te d t h a t t h i s d i s c o n t i n u i t y lo o k s s i m i l a r to t h a t w hich o c c u rs a t
f i v e m o le p e r c e n t h y d ro g en f l u o r i d e on th e io d in e p e n ta f lu o r id e - h y d r o g e n
f l u o r i d e p h ase d ia g ra m .
The two d i s c o n t i n u i t i e s m e n tio n e d above a re p ro b a b ly due to a s o l i d
s t a t e p h a se c h a n g e .

Many s u b s ta n c e s a re c a p a b le o f e x i s t i n g i n v a r io u s

c r y s t a l l i n e fo rm s w h ich a r e so r e l a t e d t o one a n o th e r t h a t a t a g iv en
te m p e r a tu re th e r e l a t i v e s t a b i l i t y o f each p a i r o f a l l o t r o p i c form s u n d e r­
goes a c h a n g e .

E ach c r y s t a l l i n e v a r i e t y h a s i t s own s o l u b i l i t y and th u s

t h e r e i s a b r e a k i n t h e s o l u b i l i t y cu rv e a t th e t r a n s i t i o n te m p e r a tu r e .

70

T h is i s a r a t h e r common o c c u rre n c e , two exam ples o f w hich a re w a te r
s o l u t i o n s o f ammonium n i t r a t e *6 and t h a l l o u s p i c r a t e . 46
I t i s q u i t e p o s s i b l e t h a t a t r a n s i t i o n o f t h i s ty p e w ould n o t have
b e e n d e t e c t e d b y t h e s im p le d e v ic e u se d i n t h i s w ork.

The p h ase change

w hich o c c u r s when a l l t h e m a t e r i a l i s i n th e s o l i d s t a t e may ta k e a v e ry
lo n g tim e t o come t o e q u i l i b r i u m .

I f t h i s was th e c a s e th e c u rv e ob­

t a i n e d i n t h i s w ork w ould have b e e n sm o o th , as in d e e d i t w as.

The p h a se

d ia g ra m , h o w ev er, m ig h t show th e change o b s e rv e d b e c a u se o f th e change
i n s o l u b i l i t y o f t h e new c r y s t a l l i n e fo rm .
The u n u s u a l concave sh a p e o f th e brom ine p e n ta f lu o r id e - h y d r o g e n
f l u o r i d e p h a s e d iag ram a t low hydrogen f l u o r i d e c o n c e n tr a tio n s h a s b een
known t o o c c u r i n o th e r s y s te m s .

The sy stem i r o n - f e r r o u s s u l f i d e i s

an exam ple4 *7 i n w hich th e p h a se diagram i s t h a t o f a sim p le two component
sy ste m e x c e p t f o r th e sh ap e a t low i r o n c o n c e n t r a t i o n s .

The sy stem i r o n -

f e r r o u s s u l f i d e d o es n o t form s o l i d s o l u t i o n s .
A con cav e f r e e z i n g cu rv e may som etim es be e x p la in e d on th e b a s i s o f
s o l i d s o l u t i o n f o r m a tio n .

The c o o lin g c u rv e s o b ta in e d i n th e r e g io n s

o f t h e t r a n s i t i o n s i n d i c a t e d , h o w ev er, t h a t th e m ix tu re c o n ta in e d l i q u i d
down t o te m p e r a tu re s n e a r th o s e o f th e e u t e c t i c p o i n t .

T h is q u a l i t a t i v e

o b s e r v a tio n was made by m anual s h a k in g o f th e a p p a r a tu s a f t e r th e s t i r r e r
h ad jammed due t o f r e e z i n g .

An o b s e r v a tio n o f t h i s ty p e would n o t

e l i m i n a t e th e p o s s i b i l i t y o f s o l i d s o l u t i o n fo rm a tio n w ith a v e ry s te e p
s o lid u s - liq u id u s c u rv e .

71

H e a ts o r F u s io n
The h e a ts o f f u s io n o b ta in e d from th e c r y o s c o p ic d a t a a re p r e s e n te d
i n T a b le X,

I n g e n e r a l i f th e y a r e com pared w ith h e a ts o f f u s i o n c a lc u ­

l a t e d from h e a t s o f v a p o r i z a t i o n and h e a t s o f s u b lim a tio n th e agreem ent
i s v ery p o o r.

The h e a ts o f f u s io n o f t a i n e d h e re f o r io d in e p e n t a f l u o r i d e

and brom ine p e n t a f l u o r i d e a r e 2 .6 9 and 1 .0 k i l o c a l o r i e s p e r m o le , r e ­
s p e c t i v e l y , w h ile th o s e c a l c u l a t e d from R u f f 's d a t a on th e v a p o r p r e s s u r e
o f t h e s o l i d com bined w ith h e a t s o f v a p o r iz a tio n o b ta in e d i n t h i s
l a b o r a t o r y 4 9 >eo a r e 3 .8 0 and 1 .7 6 k i l o c a l o r i e s p e r m o le , r e s p e c t i v e l y .
A p o s s i b l e e x p la n a tio n o f t h e s e r e s u l t s i s t h a t th e assu m p tio n t h a t s o l i d
s o l u t i o n s a r e n o t form ed i s i n c o r r e c t .

A c tu a lly i t i s p o s s ib le t h a t

s o l u t i o n s w ith a v e ry s t e e p l i q u i d u s - s o l i d u s c u rv e a r e fo rm ed .

T h is would

i n v a l i d a t e any h e a t o f f u s i o n c a l c u l a t i o n s b a s e d upon th e p h ase diagram s
p re s e n te d .

72

VI

DENSITIES AND AVERAGE MOLAR VOLUMES OF HALOGEN FLUORIDEHYDROGEN FLUORIDE SOLUTIONS
A . T h e o r e t i c a l A s p e c ts

A p a r t i a l m o la l q u a n t i t y i s d e f in e d as th e p a r t i a l d e r i v a t i v e o f
an e x te n s iv e q u a n t i t y w ith r e s p e c t t o th e number o f m oles o f a p a r t i c u l a r
s u b s t i t u e n t , when ta k e n a t c o n s ta n t te m p e r a tu r e , p r e s s u r e , and c o m p o s itio n .
T hus th e p a r t i a l m o la l volum e o f s u b s t i t u e n t 1 i n a tw o-com ponent s o l u t i o n
is
u)
w here V i s th e volume o f th e s o l u t i o n , P and T a re th e p r e s s u r e and
t e m p e r a t u r e , r e s p e c t i v e l y , and n A and n 2 a re th e number o f m oles o f each
c o n s titu e n t.
T h ere a r e a number o f g e n e r a l r e l a t i o n s b etw e e n p a r t i a l m o la l quan­
t i t i e s w h ich a p p ly t o t h e s e q u a n t i t i e s f o r any e x te n s iv e p r o p e r t y .

In

g e n e ra l

w here G i s t h e e x te n s iv e p r o p e r ty and t h e same r e s t r i c t i o n s and d e f i ­
n i t i o n s g iv e n above h o l d .
S in c e i n e a c h o f th e above e q u a tio n s th e c o n c e n tr a tio n o f th e re m a in ­
i n g c o n s t i t u e n t s re m a in s c o n s t a n t , f o r a change i n G a t c o n s ta n t te m p e r­
a tu r e and p r e s s u r e
13)

73

or

dG = Gxdnx

+ G2dn 2

+

. .

(i±)

I f th e r e l a t i v e p r o p o r t i o n s o f th e c o n s t i t u e n t s rem ain u n ch an g ed 3 th e n
i n t e g r a t i o n from nx = n 2 = 0 and G - 0 t o nx - n x , n 2 - nz , and G = G
y ie ld s
G = G-jnx

+

G2n 2

+

.

.

(5 )

F o r any i n f i n i t e s i m a l change i n c o m p o sitio n
dG

=

n 1 c)G1 + Gx c)nx

+

n 2 ^G 2

+

G2 c?n2

+

.

.

.

and s u b t r a c t i n g (,£) from (6 )
n A <) Gj_ + n 2

'd

G2

+

.

.

+
+

n
113

.

= 0

(7)

and d i v i d i n g b y c* n x
'd

tii

(5,
_
nx

375
'd n x

0

Cb)

When d e a l i n g w ith one mole o f s o l u t i o n we may d e f in e th e av erag e
v a lu e o f th e e x t e n s iv e p r o p e r t y p e r m ole as
gi

=

and s in c e n 1 + n 2

-— 2
nx + n2
+ . .

+

(9 )

. = 1 , and w1 + n 2 + .

.

.

- 1,

(10)

from E q u a tio n 5>
gi *
D iv id in g E q u a tio n

G^ n x +
7b y

G2n 2 +. .

+ n2 +

+
and d i v i d i n g th e above by 3 N j

+

.

*

. .w e
. .

^ ll)

o b ta in
.

-

0

U 2)

C6)

714

Ni

1

d Nx

•

]\t

Wa

i.

2^3

.

+

*

*

*

= o

(i

J

U 3;

W ith a tw o-com ponent s o l u t i o n i t i s p o s s i b l e t o p l o t the- a v e ra g e
v a lu e o f th e e x t e n s iv e p r o p e r t y p e r m ole ,

, v e r s u s m ole f r a c t i o n ,

The t a n g e n t t o th e c u rv e o b ta in e d a t any p o i n t w i l l i n t e r s e c t th e o r d i ­
n a t e s o f e a c h p u r e com ponent a t p o i n t s w h ich a r e th e p a r t i a l m o la l
volum es o f t h e s u b s t i t u e n t s i n q u e s tio n a t th e c o m p o sitio n o f th e p o i n t
a t w hich t h e t a n g e n t to u c h e s th e c u rv e .
B.

A p p a ra tu s and M ethod

To c a l c u l a t e th e a p p a r e n t m o la l volum es and e q u iv a le n t c o n d u c ta n c e s
o f t h e h a lo g e n f l u o r i d e - h y d r o gen f l u o r i d e s o lu t i o n s a t 2£°C , i t was
n e c e s s a r y t o d e te rm in e th e d e n s i t i e s o f th e s o l u t i o n s a t 23>°C.

The

p y cn o m eter i l l u s t r a t e d i n F ig u r e 26 was c o n s tr u c te d f o r t h i s p u r p o s e .
S in c e i t was e x tr e m e ly d i f f i c u l t t o f i l l th e pycnom eter t o a g iv e n
m ark w h ile i t was on t h e vacuum l i n e , i t was c a l i b r a t e d s e p a r a t e l y f o r
ea ch s o l u t i o n , a c c o r d in g t o th e f o llo w in g p r o c e d u r e .
w eighed and p la c e d on th e vacuum l i n e .

The pycnom eter was

S o lu tio n s w ere p r e p a re d and

w e ig h ts o f ea ch com ponent were d e te rm in e d i n th e same m anner as w i l l be
d e s c r ib e d f o r t h e c o n d u c ta n c e c e l l , e x c e p t t h a t each s o l u t i o n was p r e p a r e d
from a new sam ple o f h a lo g e n f l u o r i d e .

I t was n e c e s s a r y t o have th e u p p er

l e v e l o f t h e s o l u t i o n come up i n t o th e n a rro w neck o f th e p y c n o m e te r.
The p y c n o m e ter was th e n p la c e d i n a w a te r b a th a t 25>°C and when e q u i­
l ib r iu m was re a c h e d t h e h e ig h t o f th e s o l u t i o n i n th e n e c k was m arked.
The p y c n o m e te r was t h e n c le a n e d and r e -w e ig h e d .

Benzene a t 25°C was

75

added t o t h e m ark and i t was w eighed a g a in .

Knowing th e d e n s it y o f th e

b e n zen e , t h e volume o f s o l u t i o n w hich th e p y cn o m eter had c o n ta in e d c o u ld
b e d e te r m in e d .
A somewhat s m a lle r p y cn o m eter was u se d f o r t h e io d in e p e n t a f l u o r i d e
s o l u t i o n s , b u t t h e p ro c e d u re fo llo w e d was th e sam e.
C.

D ata and C a lc u l a tio n s

S in c e th e d a t a r e q u i r e d f o r th e c a l c u l a t i o n o f th e d e n s i t i e s o f th e
s o l u t i o n s a ls o was s u f f i c i e n t t o c a l c u l a t e th e av e ra g e m o la l volume o f
th e s o l u t i o n b y t h e u s e o f
v*
1

*

Volume o f S o lu tio n M easured
T o ta l number o f moles’ ’ '

where v i i s t h e a v e ra g e m o la l v o lu m e, t h i s q u a n t i t y h a s b e e n c a l c u l a t e d
f o r e a c h s o l u t i o n and i s g iv e n i n th e t a b l e on page 7 7 .

The i d e a l m o la l

volume o f th e s o l u t i o n was a ls o c a l c u l a t e d from
vi

-

« X VX +

N2f a

w here v i i s t h e i d e a l m o la l volume o f th e s o l u t i o n ,
m ole f r a c t i o n s o f c o n s t i t u e n t s 1 and 2 , and

and Na a re th e

and V3 are th e m o la l

volum es o f t h e p u re c o n s t i t u e n t s .
I n o r d e r t o g iv e a b e t t e r p i c t u r e o f th e change i n volume due to
n o n - i d e a l i t y , t h e p e r c e n t change i n ^

A v-j/ ( p e r c e n t)

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------------ — t-------A—

76

R > yyyy

F ig u r e 2 6 # The p y c n o m e te r; a l l p a r t s a re o f
f lu o r o t h e n e e x c e p t th e clam p in g d e v i c e .

77

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70

S in c e t h e d e n s i t i e s a r e e s tim a te d t o be a c c u r a te to ab o u t one p e r ­
c e n t , i t i s o b v io u s t h a t if* th e v a lu e s o f

a re low th e y w i l l o n ly

b e i n d i c a t i v e o f t h e o r d e r o f m ag n itu d e o f th e e f f e c t .

D.

D is c u s s io n o f th e R e s u lts

The p r im a r y r e a s o n f o r th e d e te r m in a tio n o f th e d e n s i t i e s o f th e
h y d ro g en f l u o r i d e s o l u t i o n s o f some o f th e h a lo g e n f l u o r i d e s was to
o b t a i n d a t a f o r th e c a l c u l a t i o n o f th e e q u iv a le n t c o n d u c t i v i t i e s w hich
a r e d is c u s s e d i n t h e n e x t s e c t i o n .

The v a lu e s o b ta i n e d , w hich a re g iv e n

i n T a b le XI and p l o t t e d on F ig u re 2 7 , were s u f f i c i e n t f o r t h a t p u r p o s e .
The v a lu e s o b ta in e d f o r p e r c e n t

a re s m a ll, n e g a tiv e , and

o f th e o r d e r o f m ag n itu d e o f f i v e p e r c e n t o r l e s s .

T h is i n d i c a t e s t h a t

f o r t h e s e s o l u t i o n s t h e r e i s alw ays a s m a ll d e c re a s e i n th e a v e ra g e m o la l
volum es o f th e s o l u t i o n s , and th u s th e r e i s alw ays a s m a ll d e c re a s e in
th e p a r t i a l m o la l volum es o f th e c o n s t i t u e n t s upon m ix in g .

T h is m ig h t

i n d i c a t e t h a t t h e p u re s u b s t i t u e n t s have a more open s t r u c t u r e i n th e
liq u id s ta te .

The h y d ro g en bonded s t r u c t u r e o f h y d ro g en f l u o r i d e , f o r

e x a m p le , may be b ro k e n up i n th e s o l u t i o n .
may o c c u r i n th e m ix tu r e .

A ls o , some ty p e o f a s s o c i a t i o n

B o th o f th e s e e f f e c t s m ig h t o c c u r.

T h e re i s o n ly one p r e v io u s r e p o r t on p a r t i a l m o la l volum es i n a
h a lo g e n f l u o r i d e s y s te m .

S t e in and V ogel

have s tu d ie d th e system

b ro m in e t r i f l u o r i d e - b r o m i n e p e n t a f l u o r i d e and have r e p o r te d a d e c re a s e
o f l e s s th a n one p e r c e n t i n th e p a r t i a l m o la l volum e.

79

3 .0

D e n s ity

25

2 .0

1.0

o

25

5o

75

loo

W eig ht P e r c e n t H ydrogen F lu o r id e
F ig u re 2 7 . D e n s i t i e s o f h y d ro g en f l u o r i d e s o l u t i o n s o f some
h a lo g e n f l u o r i d e s : A , io d in e p e n t a f l u o r i d e ; B , brom ine p e n ta ­
f lu o r i d e ; C , c h lo r in e t r i f l u o r i d e .

80

V II

CONDUCTANCE STUDIES OF THE HALOGEN FLUORIDES AND
THEIR HYDROGEN FLUORIDE SOLUTIONS
A.

T h e o r e t i c a l A s p e c ts 61
M easurem ent

When an e l e c t r i c a l p o t e n t i a l d i f f e r e n c e i s a p p lie d t o a l i q u i d con­
t a i n i n g i o n s , t h e io n s w i l l be s u b je c te d t o an a c c e l e r a t i n g f o r c e w hich
w i l l g iv e r i s e t o an e l e c t r i c c u r r e n t .

G e n e ra lly i t i s fo u n d , h o w ev er,

t h a t when d i r e c t c u r r e n t m easurem ents a r e made th e r e s i s t a n c e o f th e
l i q u i d d oes n o t s t r i c t l y obey Ohm*s law b e c a u s e o f e l e c t r o d e p r o c e s s e s
w hich may te n d t o i n c r e a s e th e a p p a re n t r e s i s t a n c e o f th e l i q u i d .
T h is e f f e c t i s l a r g e l y o f f s e t b y th e u s e o f an a l t e r n a t i n g e l e c t r i c
fie ld .

T hus th e m easurem ent becom es an im pedance r a t h e r th a n a r e s i s t a n c e

m ea su re m e n t.

The c u r r e n t w hich r e s u l t s from t h e u se o f an a l t e r n a t i n g

f i e l d stem s from two s o u r c e s .

The f i r s t , and t h e one w hich i s o f m a jo r

im p o rta n c e h e r e , i s th e m ig r a tio n o f io n s i n th e f i e l d .
r e o r i e n t a t i o n o f th e c h a rg e d i s t r i b u t i o n .

The second i s

At f r e q u e n c ie s i n th e au d io

ra n g e th e c u r r e n t com ponent w hich I s due t o r e o r i e n t a t i o n i s n o t con­
d u c tiv e s in c e no n e t lo n g ra n g e m ig r a ti o n c an o c c u r and th e r e d i s t r i b u t i o n
c a n ta k e p l a c e i n a v e r y s h o r t t im e .
When c o n d u c ta n c e m easu rem ents a r e made i n th e ra n g e o f a u d io f r e ­
q u e n c ie s i t h a s b e e n found® 2 t h a t p a r t o f th e m easu red Impedance i s n o t
due to t h e s o l u t i o n i t s e l f , b u t as i n th e d i r e c t c u r r e n t m easu rem en ts,
i s due t o e l e c t r o d e p r o c e s s e s .
and a r e a c t i v e com ponent.

T h is e f f e c t may have b o th a r e s i s t i v e

G e n e r a lly t h e s e e f f e c t s c a n be e lim in a te d , by t h e u se o f p l a t i n i z e d —
p la tin u m e l e c t r o d e s , th e v e r y la r g e s u r f a c e a r e a o f w hich re d u c e s th e
e l e c t r o d e r e a c t a n c e s t o a n e g l i g i b l e m a g n itu d e .

I n t h i s w o rk , how ever,

th e n a t u r e o f t h e s o l u t i o n s whose c o n d u c ta n c e was b e in g m easu red made i t
n e c e s s a r y t o u s e u n p l a t i n i z e d p la tin u m e le c t r o d e s s in c e a f i n e l y d iv id e d
s u r f a c e w ould h av e b e e n c h e m ic a lly a t t a c k e d .
I n o r d e r to overcom e th e above d i f f i c u l t i e s u se h a s b een made o f th e
f a c t t h a t t h e r e s i s t i v e and r e a c t i v e com ponents o f th e e l e c tr o d e p r o ­
c e s s e s h av e b e e n fo u n d t o v a ry a p p ro x im a te ly l i n e a r l y w ith th e in v e r s e
s q u a re r o o t o f th e f r e q u e n c y .13

Thus i f th e sum o f th e r e s i s t i v e com­

p o n e n ts o f t h e s o l u t i o n and o f th e e le c tr o d e p r o c e s s e s a r e p l o t t e d a g a in s t
th e i n v e r s e s q u a re r o o t o f th e fre q u e n c y and e x tr a p o l a te d t o i n f i n i t e
f r e q u e n c y , th e r e s i s t i v e com ponent o f th e s o l u t i o n a lo n e i s o b ta in e d .
S p e c i f i c and E q u iv a le n t C on d u ctan ces
The s p e c i f i c c o n d u c ta n c e o f a c o n d u c to r i s d e f in e d a s th e r e c i p r o c a l
o f th e r e s i s t a n c e o f a cube w ith s id e s one s q u a re c e n tim e te r i n a r e a , and
h a s u n i t s o f r e c i p r o c a l ohms p e r cm.
S in c e i t i s o b v io u s ly v e ry d i f f i c u l t and i m p r a c t i c a l to d e s ig n a
c e l l o f e x a c t l y th e s e d im e n s io n s , a g iv e n co n d u c ta n c e c e l l i s c a l i b r a t e d
b y th e u s e o f a s o l u t i o n o f known c o n d u c ta n c e .
The r e s i s t a n c e o f any c o n d u c to r o f c o n s ta n t c r o s s s e c t i o n a l a r e a v a r i e s
d i r e c t l y w ith i t s l e n g t h (d ) and i n v e r s e l y w ith i t s a r e a (.&) •

That i s

b2

w here R i s t h e t o t a l r e s i s t a n c e and

<p i s th e s p e c i f i c r e s i s t i v i t y .

Jn

t h i s work we s h a l l d e s ig n a te th e s p e c i f i c c o n d u c ta n c e by L and th u s
L

1

ohms

cm

By Ohm*s law

where I i s t h e c u r r e n t , S i s th e a p p lie d p o t e n t i a l and K i s a c o n s ta n t
known as th e c e l l c o n s ta n t and h a s u n i t s o f r e c i p r o c a l c e n t i m e t e r s .
K c a n be d e te rm in e d f o r any c e l l i f R i s m easured when th e c e l l c o n ta in s
a s o l u t i o n o f known s p e c i f i c c o n d u c ta n c e .
F o r a g iv e n e l e c t r o l y t e th e q u a n t i t y o f e l e c t r i c i t y w hich a s o l u t i o n
ca n c a r r y d ep en d s upon t h e number o f c u r r e n t c a r r y in g p a r t i c l e s c o n ta in e d
i n a g iv e n volum e and th u s upon t h e c o n c e n tr a tio n o f th e c u r r e n t c a r r y in g
s p e c ie s .

I n o r d e r t o d e te rm in e th e c u r r e n t c a r r y i n g a b i l i t y o f a l l th e

io n s p ro d u c e d b y a s o l u t e a q u a n ti ty c a l l e d th e e q u iv a le n t co n d u ctan ce i s
d e fin e d .

I t i s a m easu re o f th e c u r r e n t c a r r y in g power o f a l l th e io n s

r e s u l t i n g from th e d i s s o c i a t i o n o f one g ra m -e q u iv a le n t o f t h e s o l u t e .

In

a c t u a l p r a c t i c e t h i s q u a n t i t y i s o b ta in e d from th e s p e c i f i c co n d u ctan ce
by m u l t i p l y i n g th e s p e c i f i c c o n d u c ta n c e b y th e volume o f s o lu t i o n o c c u p ie d
b y one gprarn e q u i v a l e n t o f th e s o l u t e .

The e q u iv a le n t co n d u ctan ce / \ i s

t h e r e f o r e o b ta in e d from
/\

=

L V

-

1000 L

E q u iv a le n t c o n c e n tr a tio n

The e q u i v a l e n t c o n d u c ta n c e o f s t r o n g e l e c t r o l y t e s g e n e r a lly ap p ro ach es a
l i m i t i n g v a lu e a t i n f i n i t e d i l u t i o n .

T h is i s p resu m ab ly a m easure o f

t h e c o n d u c tin g pow er o f one g r a m -e q u iv a le n t o f th e e l e c t r o l y t e when i t

63

i s c o m p le te ly d i s s o c i a t e d .

V ery o f t e n t h e m o lar co n d u c ta n c e M i s u s e d .

F o r u n i - e q u i v a l e n t s u b s ta n c e s M and A

a re i d e n t i c a l .

The e q u i v a l e n t c o n d u c ta n c e s o f weak e l e c t r o l y t e s depend upon th e
d e g re e o f i o n i z a t i o n , and th u s as th e c o n c e n tr a tio n becom es v e r y low
t h e i n c r e a s i n g i o n i z a t i o n c a u s e s a s h a rp in c r e a s e i n c o n d u ctan ce so
t h a t an e x t r a p o l a t i o n t o i n f i n i t e d i l u t i o n i s p r a c t i c a l l y im p o s s ib le i n
a c tu a l p r a c t i c e ,
I n g e n e r a l , f o r w a te r s o l u t i o n s , th e e q u iv a le n t co n d u c ta n c e i n c r e a s e s
w ith i n c r e a s i n g te m p e r a tu re owing t o d e c r e a s in g v i s c o s i t y o f th e medium.
W ith weak e l e c t r o l y t e s , ho w ever, t h i s i s n o t alw ay s t r u e .

The c o n d u c t­

an ce o f weak e l e c t r o l y t e s depends p r i n c i p a l l y upon th e d e g re e o f i o n i z a ­
t i o n o f t h e e l e c t r o l y t e and s in c e weak e l e c t r o l y t e s p ro b a b ly have a
d e f in ite h e a t o f io n iz a tio n in s o lu tio n t h i s can cause a d e crease in
i o n i z a t i o n w ith i n c r e a s i n g t e m p e r a tu r e .

I n p r a c t i c e th e e q u iv a le n t con­

d u c ta n c e s o f weak e l e c t r o l y t e s a r e o f t e n o b s e rv e d t o in c r e a s e to a
maximum and th e n d e c r e a s e as th e te m p e ra tu re i s in c r e a s e d .
h o n -aq u e o u s S o lu tio n s
The above d i s c u s s io n a p p l ie s p r i n c i p a l l y t o s o lu t i o n s i n w a te r .
A c tu a lly o t h e r s o lv e n t s c o v e r a w ide ra n g e o f s i m i l a r i t y o r d i s s i m i l a r i t y
t o w a te r d e p e n d in g upon t h e i r i o n i z i n g power and th u s upon t h e i r d i ­
e le c tr ic c o n s ta n t.

A lth o u g h s o lv e n ts o f h ig h d i e l e c t r i c c o n s ta n t v e ry

o f te n show c o n d u c ta n c e b e h a v io r s i m i l a r t o t h a t o f w a te r s o l u t i o n s , a
c a s e i n p o i n t b e in g h y d ro g en f l u o r i d e s o l u t i o n s , 1®^>®s w ith s o lv e n ts o f

bh

low d i e l e c t r i c c o n s t.a n t i t i s v e r y o f t e n fo u n d t h a t th e r e i s a minimum
i n t h e e q u i v a l e n t c o n d u c ta n c e a t some c o n c e n t r a t i o n .

I n aqueous s o lu ­

t i o n s th e e q u i v a l e n t c o n d u c ta n c e r i s e s s t e a d i l y as d i l u t i o n i s i n c r e a s e d .
The c o n d u c ta n c e minimum a p p e a rs t o move to h ig h e r c o n c e n tr a tio n s as th e
d i e l e c t r i c c o n s ta n t o f th e medium i n c r e a s e s .
The e q u i v a l e n t c o n d u c ta n c e s o f s tr o n g e l e c t r o l y t e s a t i n f i n i t e d i ­
l u t i o n i n s o l v e n t s su c h a s a l c o h o l s , n i t r i l e s o r n i t r o - d e r i v a t i v e s can
b e o b ta in e d b y m ethods s i m i l a r t o t h a t f o r w a te r .

F o r m ed ia o f low d i ­

e l e c t r i c c o n s ta n t s u c h a p r o c e d u re i s n o t p o s s i b l e .

B.

A p p aratu s and M ethod

The C onductance B rid g e
The c o n d u c ta n c e b r id g e u s e d i n t h i s work h a s been d e s c r ib e d i n d e t a i l
e l s e w h e r e .13

The b r id g e c o n s is te d p r i n c i p a l l y o f an a u d io -fre q u e n c y

g e n e r a t o r , a s e l e c t i v e d e t e c t o r , and th e b r id g e c i r c u i t ; th e l a t t e r i n ­
c lu d e d a r a t i o b o x , s ta n d a r d r e s i s t o r s and s ta n d a r d c a p a c i t o r s .

B alan c e

was d e t e c t e d on an o s c il l o s c o p e b y means o f L issa jjo u s f i g u r e s , and a
r e f e r e n c e s i g n a l was u s e d t o g iv e t h e h o r i z o n t a l d e f l e c t i o n .

The o s c i l l o ­

sco p e was u s e d i n su c h a m anner t h a t b o th th e m agnitude and t h e r e l a t i v e
p h a se o f t h e b r id g e o u t p u t c o u ld b e o b s e rv e d .

Thus i t was p o s s ib le to

o b s e rv e b o th Rs and C s , th e r e s i s t a n c e and c a p a c ita n c e s e t t i n g s a t b a l a n c e ,
on th e s ta n d a r d d e c a d e s .
shown i n F ig u r e 2 8 .

A s i m p l i f i e d c i r c u i t diagram o f th e b r id g e i s

65

F ig u r e 2 8 . S im p lif ie d b r id g e c i r c u i t : Rj. and Ra a r e 1 :1 r a t i o
r e s i s t o r s ( R ^ R a ) ; Rs 1S a s ta n d a r d d ecad e r e s i s t a n c e b o x , Cs
i s a s ta n d a r d d ecad e c a p a c ita n c e b o x ; Rx and Cx a r e th e r e ­
s i s t i v e and c a p a c i t i v e com ponents o f th e unknown im pedance;
D i s t h e d e t e c t o r ; a / i s th e s i g n a l g e n e r a t o r .

The b r id g e i s a t b a la n c e when Cx and Rx a r e e q u iv a le n t t o th e p a r a l l e l
c o m b in a tio n o f Rs and Cs .

I t h a s b e e n shown12 t h a t
Rs

Rx

”

1

+ Cl>x Cs 2 Rs a

Thus i t i s s e e n t h a t i t i s n e c e s s a r y t o know th e fre q u e n c y i n o rd e r t o
c a l c u l a t e Rx .

The s i g n a l g e n e r a to r p ro d u ced f i v e f ix e d f r e q u e n c ie s .

T hese w ere UOOO, 2 0 0 0 , 1 0 0 0 , 6 0 0 , and U00 c y c le s p e r s e c o n d , r e s p e c t i v e l y .
I n o r d e r t o o b t a i n a p l o t o f Rx v e r s u s 1/V T “ > m easurem ents o f Rx were
made a t e a c h o f th e above f r e q u e n c ie s f o r a g iv e n co n d u ctan ce m easu rem en t.

86

The C o n d u ctan ce C e ll s
C e ll d e s ig n .
u s e d i n t h i s w o rk .

The tw o c e l l s i l l u s t r a t e d i n F ig u r e s 29 and 30 were
They w ere b o th c o n s tr u c te d e n t i r e l y o f f lu o r o th e n e

e x c e p t f o r t h e p la tin u m p l a t e s , p la tin u m l e a d s , and c o p p e r - c o n s ta n ta n
th e rm o c o u p le s *

C e l l I was u se d f o r p u re io d in e p e n t a f l u o r i d e and f o r

i o d i n e p e n ta f lu o r id e - h y d r o g e n f l u o r i d e m ix tu r e s .

C e l l I I was u s e d f o r

p u re c h l o r in e t r i f l u o r i d e , p u r e brom ine p e n t a f l u o r i d e , and f o r t h e i r
h y d ro g e n f l u o r i d e s o l u t i o n s .
The o n ly m a jo r d i f f e r e n c e b etw een th e two c e l l s was t h a t i n C e l l I
f lu o r o th e n e wax was u s e d e x t e n s iv e ly f o r s e a l i n g p u r p o s e s .

The u se o f

wax was a v o id e d i n C e l l I I b e c a u s e i t s h ig h s o l u b i l i t y i n brom ine
p e n t a f l u o r i d e and i n c h l o r i n e t r i f l u o r i d e gave t r o u b l e .

C e ll I I was a ls o

d e s ig n e d t o have a much lo w er c e l l c o n s ta n t th a n c e l l I b e c a u se o f th e
v e ry low c o n d u c t i v i t i e s o f b rom ine p e n t a f l u o r i d e and c h l o r in e t r i f l u o r i d e .
I t was n e c e s s a r y t o change th e wax i n C e l l I a f t e r each u s e w ith
h y d ro g en f l u o r i d e .

Such a p ro c e d u re was n o t n e c e s s a r y w ith C e l l I I .

As can b e s e e n i n th e i l l u s t r a t i o n s , th e c e l l s a r e o f th e d ip p in g
e l e c t r o d e ty p e and were c o n s tr u c te d so t h a t th e e n t i r e e l e c tr o d e assem bly
i s a p a r t o f th e ta p e r e d p lu g w hich f i t s i n t o th e t u b e .

In b o th c e l l s

th e p la tin u m l e a d s w ere s h i e l d e d so t h a t th e l e v e l o f th e l i q u i d d id n o t
e f f e c t th e c e l l c o n s t a n t .

B oth c e l l s w ere f i t t e d w ith v a lv e s so th e y

c o u ld b e a tta c h e d d i r e c t l y t o th e vacuum l i n e and th e s o lu t i o n s p r e p a re d
d i r e c t l y i n th e m .

P l a t e 5* C onductance c e l l I I

a?

F ig u r e 2 9 , C o n d u ctan ce c e l l i ; A, f lu o r o th e n e th erm o co u p le
w e l l ; B and C , t lu o r o th e n e wax s e a l s ; D , f lu o r o th e n e
in s u la tio n .

88

Bottom v ie w o f
e l e c t r o d e assem b ly

S ide v iew

F ig u re 3 0 . C o n d u ctan ce c e l l I I ; A , f lu o r o th e n e tu b e s ;
B , T e f lo n p a c k in g p lu g ; C , f lu o r o t h e n e wax p a c k in g ;
D, th e rm o c o u p le w e ll (shown o n ly i n lo w e r p a r t o f s i d e
v ie w ) ; B, p la tin u m p l a t e s .

Ce11 c a l i b r a t i o n .

B o th c e l l s w ere c a l i b r a t e d p e r i o d i c a l l y t o d e­

te r m in e w h e th e r any change had o c c u rre d i n th e c e l l c o n s ta n ts due to
h a n d lin g .

The d a t a and p r o c e d u re s f o r some o f th e s e c a l i b r a t i o n s a re

g iv e n h e r e .
C e l l I was i n i t i a l l y c a l i b r a t e d o v e r th e ra n g e o f te m p e ra tu re from
a b o u t 0 t o 30°C u s in g a v e ry d i l u t e p o ta ss iu m c h lo r id e s o l u t i o n .
p o ta ss iu m c h l o r i d e s o l u t i o n c o n ta in e d O.3663
1000 c c . o f w a t e r .

The

p o ta ss iu m c h l o r id e p e r

The d a t a o b ta in e d a r e g iv e n i n T a b le X I I .

S in c e t h e c o n c e n t r a t i o n o f th e s ta n d a r d s o l u t i o n was lo w e r th a n
t h o s e f o r w h ich c o n d u c ta n c e d a t a i s g iv e n i n s ta n d a r d c o n d u c ta n c e t a b l e s ,
t h e d a t a o f B re n n e r64 and S h edlovsky66 were u se d t o c a l c u l a t e th e s p e c i f i c
c o n d u c ta n c e o f t h e p o ta s s iu m c h l o r id e s o l u t i o n o v e r th e te m p e r a tu re ra n g e
in d ic a te d .

B re n n e r t a b u l a t e d th e c o e f f i c i e n t s b e lo w v e r s u s te m p e r a tu re and

p o ta s s iu m c h l o r i d e c o n c e n t r a t i o n .
e ffic ie n ts

d A
yv d V -----

p e r l i t e r o f w a te r.
T em pnature °C
d A

A dt

o b ta in e d

f o r O.3663 gm p o ta ss iu m c h lo r id e

The u n i t s o f A

0
0298

U sin g h i s d a t a th e f o llo w in g c o -

5

a r e cm2 e q u iv ^ o h m " 1 .

10

.0272

15

. 021*9

.0229

20
.0212

25
.0197

S h ed lo v sk y d e te rm in e d th e e q u iv a le n t c o n d u c ta n c e s o f p o ta ssiu m
c h l o r id e s o l u t i o n s a t 18 and 2 5 °C .

The e q u iv a le n t c o n d u c ta n c e o f th e

above p o ta s s iu m c h l o r i d e s o l u t i o n i s 1 2 1 .0
11*3.6 ohm"1 cm" 1 a t 25°C .

ohm**1 cm"1 a t 18°C , and

The e q u iv a l e n t c o n d u c ta n c e s o f th e above

p o ta ss iu m c h l o r i d e s o l u t i o n a t v a r io u s te m p e r a tu re s w ere d e te rm in e d from
th e s e d a t a by a m ethod o f s u c c e s s iv e a p p ro x im a tio n .

90
TABLE XII
CALIBRATION OF CELL I USING A SOLUTION CONTAINING 0 . 3663 GRAMS OF'
POTASSIUM CHLORIDE PER LITER OF WATER

T e m p e ra tu re
Cs
2 9 .5

R«
y **
Ex

23.U

cs
Rs

y

Rx

c s

20.3

Rs
y

^X

18.1

cs
Rs

r

Rx

17.3

1 5 .1*

20b0

F re q u e n c y
1000

0 .0 0 8
216
0 .0 0 2
216

0 .0 3 0
219
0 .0 0 7
218

0 .0 0 7
21a
0 .0 0 2
21*0

600

1|00

0 .0 8 7
225
0 .0 1 3
222

0 .3 0
230
0 .0 7
216

0.1*0
2b7
0 .6 6
233

208

0 .0 2 7
2U3
0 .0 0 7
21a.

0 .0 9 0
25U
0 .0 1 8
2h9

0 .1 8
259
0 .0 3
251

0 .3 5
275
0 .0 6
260

229

0 .0 0 7
256
0 .0 0 2
255

0 .0 2 1
258
0 .0 0 5
257

0 .0 7 8
268
0 .0 1 5
26b

0 .1 6
273
0 .0 3
266

0 .3 0
286
0 .0 5
273

2h7

0 .0 0 6
270
0 .0 0 2
269

0 .0 1 7
272

0 .0 5 b
280
0 .0 0 7
278

0 .1 0
28b
0 .0 1
281

0 .2 0
293
0 .0 2
287

0.11*
286
0 .0 2
279

0 .2 5
300

o.ool*
271
0 .0 1 8
27b

Rtohm s)*

260

k
K

0 .0 0 7
272
0 .0 0 2
271

o.ool*
272

0 .0 6 7
28b
0 .0 1 2
280

c3

0 .0 0 5
287
0 .0 0 1
287

0 .0 1 5
291
0 .0 0 3
290

0 .0 5 3
300
0 .0 0 9
297

0 .1 0 0
303
0 .0 1
299

0 .2 0
31b
0 .0 3
306

279

0 .0 0 5
306
0 .0 0 2
306

0 .01U
309
0 .0 0 3
308

0 .0 5 1
318
0 .0 0 9
315

0 .1 0
323
0 .0 1
319

0 .2 0
335
0 .0 3
326

296

RS

y

Rx
c s

1 2 .8

boob

Rs
y
Rx

0.01*

261*

290

C o n tin u e d n e x t page

91

TABLE XII - continu ed

liOOO

2000

F re q u e n c y
1000

600

LOO

^s
Rs
X
Rx

0 .0 0 5
322
0 .0 0 2
322

0 .0 1 3
32U
0 .0 0 3
323

0.01*7
333
0 ,0 0 9
330

0 .0 1
336
0 .0 1 5
331

0 .1 b
3^8
0 .0 2 9
338

31i4

Rs
X
Rx

0 .0 0 3
U5
0 .0 0 1
Ui5

O.OOti
L i8
0 .0 0 2
1*17

0 .0 3 0
U28
0 .0 0 6
bZS

0 .0 6
h33
0 .0 1
U29

0 .1 2
U+5
0 .0 2
h37

L05

T e m p e ra tu re

9 .7

0 0

RCohms)*

* R i s o b ta in e d b y e x t r a p o l a t i n g a p l o t o f Rx v e r s u s 1 / sfT~ t o i n f i n i t e
fre q u e n c y .
** X = Cj2 Rs 2 Cs 3
Cs i s i n m i c r o f a r a d s .
Rs i s i n ohm s.

92

A sam p le c a l c u l a t i o n o f th e e q u i v a le n t c o n d u c ta n c e a t lij.0C i s g iv e n
h ere.

The mean v a lu e o f d A /

A d t b etw een 11° and 18°C i s e s tim a te d

t o be 0 .0 2 3 3 cm*1 from a p l o t o f B r e n n e r 's d a t a .
F i r s t a p p r o x im a tio n :

d A

* 0.0233 X b X 1 2 b .0 cm ^equiv-^-olun” 1
= 1 1 .6 cm2e q u iv ~ 1ohm"''1

S eco n d a p p r o x im a tio n :

d

A =
A »

1 2 lu 0 - 1 1 . 6 = 1 1 3 .0

A «

I 2b .0 - 1 0 .5 = 1 1 3 .5

0 .0 2 3 3 X b X 113

« 1 0 .5

T h is was r e p e a t e d a t 1 0 ° , 5 ° and 0 ° C u s in g i n e a c h c a s e th e v a lu e o f
A

o b ta in e d a t th e p r e c e d in g te m p e ra tu re as a f i r s t a p p ro x im a tio n .

The

s p e c i f i c c o n d u c ta n c e (L) was th e n c a l c u l a t e d from th e e q u a tio n

L

= ~!C65S------- .

oton"1™ - 1

The v a lu e s o f L v e r s u s T f o r th e s o l u t i o n o f O.3663 gm p o ta ss iu m c h lo r id e
p e r l i t e r o f w a te r a re p l o t t e d i n F ig u re 31..
U sin g th e c o n d u c ta n c e s c a l c u l a t e d i n t h i s m anner th e c e l l c o n s ta n ts
ilU w ere c a l c u l a t e d from
K

= ^KCl * ^

w here th e v a lu e s o f R a re o b ta in e d from p l o t s o f Rx v e r s u s th e in v e r s e
sq u a re r o o t o f th e fre q u e n c y .
v e r s u s te m p e r a tu r e .

F ig u re 32 i s a p l o t o f th e c e l l c o n s ta n t

S in c e we a r e m a in ly i n t e r e s t e d i n th e c e l l c o n s ta n t

a t 25°C th e s l i g h t e r r o r s c a u s e d by th e above a p p ro x im a tio n s a t lo w er
te m p e r a tu r e s a r e n o t c o n s id e r e d to b e im p o r ta n t.
A se c o n d c e l l c o n s ta n t r u n was made a t 2 lj.9 0C a f t e r s e v e r a l io d in e
p e n t a f l u o r i d e s o l u t i o n s had b e e n m e a su re d .

F o r t h i s d e te r m in a tio n a

s o l u t i o n o f 0.7U 59 gm. p o ta ss iu m c h l o r id e p e r l i t e r o f w a te r was u s e d .

20

10

7 .5

3 .5
S p e c i f i c C onductance (L)

X lO 4

F ig u r e 3 1 . S p e c i f i c c o n d u c ta n c e v e r s u s te m p e r a tu re f o r a
s o l u t i o n c o n t a i n i n g 0 . 3663 grams o f p o ta ss iu m c h lo r id e p e r
l i t e r o f w a te r.

9k

0

20

10
T em p e ratu re

F ig u re 3 2 .

The c e l l c o n s ta n t o f c e l l I a t v a r io u s te m p e r a tu r e s .

30

95

The s p e c i f i c c o n d u c ta n c e o f t h i s s o l u t i o n h a s b e e n fo u n d t o be 0.0011*10
cm"1 ohm"1 . 42

The p e r t i n e n t d a t a a re g iv e n i n T a b le X I I I .

The c e l l con­

s t a n t o f 0 .1 5 9 cm "1 i s i n c l o s e ag reem en t w ith t h a t o b ta in e d ab o v e .
TABLE X III
CALIBRATION DATA FOR CELL I USING A SOLUTION CONTAINING 0.71*59 GRAMS
POTASSIUM CHLORIDE PER LITER OF WATER AT 2l*.9°C
F re q u e n c y
1000

600

1*000

2000

1*00

Gs

0 .0 2 1

0.01*3

0.11*3

0 .2 7

o .5 3

Rs

120

122

127

125

13U

0

o.ool*

o.ool*

0 .0 1 3

0 .0 2

0 .0 3

Rx

119

121

125

123

130

R
ohm

K
cm*’1

111*

0 .1 5 9

C e l l I I was f i r s t c a l i b r a t e d o v e r a ra n g e o f te m p e r a tu re from 6 t o
21°C u s in g t h e s o l u t i o n c o n ta in in g 0.71*59 gm. p o ta ssiu m c h lo r id e p e r
l i t e r o f w a te r .

The p e r t i n e n t d a t a a r e g iv e n i n T a b le XIV.

F ig u re 33 i s

a p l o t o f s p e c i f i c c o n d u c ta n c e v e r s u s te m p e ra tu re f o r a p o ta ssiu m c h l o r id e
s o l u t i o n o f t h i s c o n c e n t r a t i o n . 42

F ig u re 3U shows a p l o t o f th e c e l l

c o n s ta n t (K) v e r s u s te m p e r a tu re f o r t h i s c e l l .
A f te r t h i s c e l l was u s e d f o r th e co n d u ctan ce ru n s w ith th e h alo g en
f l u o r i d e s and t h e i r h y d ro g e n f l u o r i d e s o lu t i o n s i t was n e c e s s a r y t o r e ­
p la c e th e b o tto m f lu o r o t h e n e s u p p o r t.
th e c e l l c o n s ta n t.
m a te ly -7 8 ° C .

T h is cau sed a s l i g h t change i n

The c e l l was th e n r e c a l i b r a t e d a t 25 0 and a t a p p ro x i­

S in c e th e c e l l c o n s ta n t a t -78°C was d e s ir e d f o r th e c e l l

96

TABLE X IV

CALIBRATION DATA FOR CELL I I

l*06 o

2000

0.15U

0 .3 6 0

0 .9 9

—

2 .7 4

Rs

UT .3

50 .u

59.0

—~

6 2.0

5

0 . 03 U

0.052

0 .1 3 5

US.7

U7 .6

5 2 .0

---

62.2

0.1 5 3

0 .3 6 3

0 .9 6

1 .7 5

2.7 5

UU.8

50.0

60.0

66*0

86.0

V

0 .0 3 5

0.052

0 .131

0 .1 9

0 .3 4

Rx

U7.2

U7.0

53.0

5 5 .5

64.0

Cs

0 .1 3 5

0 .3 0 0

0 . 6U0

1 .4 9

2.42

Rs
V

5U.1

55.5

65.5

7 2 .0

9 1 .0

0 . 03U

0 . 0W1

0.119

0 .1 6

0.31

RX

5 2 .3

53.2

5 5 .0

61.7

69.6

Cs

0 .1 0 0

0.220

0 .6 5 0

1 .1 4

1.88

Rs
v/
it

6 6 .6

69.0

80.1*

65. 4

1 0 4 .4

0 .0 2 0

0.036

0 .1 0 0

0.134

0 .2 4 4

6U.8

6 6 .6

7 2 .6

7 6 .6

83.9

T em perature

25.0

22 A

RS
V

1 6 .2

6.1

Frequency
1000
600

Rx

4<&

R
ohms

K
cm-1

h k .o

0.0622

4 6 .5

0.0623

5 2 .0

0 .0614

63 .h

O.O506

0 .3 2

0 #0010

5

10

15

20

Temperature °C
F igu re 3 3 . S p e c if ic conductance versus tem perature fo r O.OOlw
potassium c h lo r id e . Data from th e Handbook o f Chemistry and
P h y s ic s .

cm-1

20

10

Temperature
F igure

3h.

°c

C e ll con stan t o f c e l l I I a t d if fe r e n t tem peratures.

99

b e f o r e th e s u p p o r t was c h a n g e d , i t was assumed t h a t th e p e r c e n t change
a t 25°C was t h e same as th e p e r c e n t change a t -7 8 ° C .

The d a t a f o r th e

r e c a l i b r a t i o n a t 2£°C a r e g iv en i n T a b le XV.
The p ro c e d u re f o r th e c a l i b r a t i o n o f c e l l 11 a t - 78°C was as
f o llo w s :

s o l u t i o n s o f two grams o f p o ta ssiu m h y d ro x id e p e r l i t e r o f

e t h a n o l , two m i l l i l i t e r s o f c o n c e n tr a te d h y d r o c h lo r ic a c id p e r l i t e r o f
e t h a n o l , and two m i l l i l i t e r s o f c o n c e n tr a te d h y d r o c h lo r ic a c id p e r l i t e r
o f a c e to n e , w ere p r e p a r e d .

The c o n d u c ta n c e s o f th e s e s o lu t i o n s a t - 78°C

w ere d e te rm in e d a p p ro x im a te ly b y u s in g t h e g la s s c e l l i l l u s t r a t e d i n
F ig u re 3 5 ,

The m easu rem en ts were made w h ile t h i s c e l l was im m ersed i n

a D ry l c e - a c e t o n e m i x t u r e .

The c e l l c o n s ta n t o f th e g la s s c e l l has

p r e v i o u s l y b e e n shown t o b e 0 .8 8 8 a t 2 £ ° C .1:l

The t o t a l d is t a n c e betw een

t h e p l a t e s o f ' t h i s c e l l i s 3&nm. a t 2£°C and ch an g es by l e s s th a n one mm.
on c o o lin g t o - 78° C .

I t i s t h e r e f o r e r e a s o n a b le to assume t h a t th e

c e l l c o n s ta n t o f th e g l a s s c e l l changed l e s s th a n two p e r c e n t on c o o lin g .
M easurem ents w ere th e n made on th e same s o lu t i o n s i n c e l l I I a t -7 8 °C .
The d a t a f o r th e s e r u n s a r e t a b u l a t e d i n T a b le XVI.
i t c a n be s e e n from th e d a ta o f T a b le XVI t h a t when th e c e l l con­
s t a n t a t 25°C i s 0 . 05U cm"”1 , t h e a v e ra g e v a lu e f o r th e c e l l c o n s ta n t
o
a t -7 8 C i s 0 .0 6 0 „ 0 .0 0 £ .

Assum ing t h a t th e change due t o re p la c e m e n t

o f t h e s u p p o rt was t h e same a t e a c h te m p e r a tu r e , th e c e l l c o n s ta n t was
0 .0 7 1 t 0 .0 0 6 cm"1 a t -78°C when i t was 0 .0 6 2 2 cm" 1 a t 25°C .

100

TABLE XV
RECALIBRATION OF CELL I I AT 25°C
F re q u e n c y

1*000

2000

1000

600

Cs

0 .0 3 3

0 .0 6 3

0.360

0.666

Rs

3 9 .0

3 9 .2

Uo.o

1*0.0

*

0.001

0.002

0 .0 0 8

0.010

Rx

3 9 .0

3 9 .1

3 9 .7

3 9 .6

R
oftm

K
cm“ i

38.6

0.05U 1

101

F igu re 3 5 . The g la s s conductance c e l l ; A, mercury co n ta ct;
B , platinum e le c tr o d e s .

102

TABLE XVI
CALIBRATION OF CELL I I AT -?0°C
F req u e n c y
C e ll

iiOOO

2000

1000
olims

D
600

1*00

ohm

v
cm"1

A . Two gram s o f p o ta ss iu m h y d ro x id e p e r l i t e r o f e th a n o l
G lass
C e ll I I

30,800

31,200

31,700

32,000

32,200

29,500

1,81*0

1,850

1 ,8 5 0

1 ,8 5 0

1 ,8 5 0

1 ,8 5 0

0 .0 5 5

B . Two m i l l i l i t e r s o f c o n c e n tr a te d h y d r o c h lo r ic a c id p e r
l i t e r o f e th a n o l.
G lass

3 2 ,2 0 0

3 2 ,9 0 0

3 3 ,^ 0 0

33,6 0 0

3 3 ,7 0 0

C e l l 11

.2,250

2,250

2,260

2,260

2,260

3 0 ,5 0 0

2 , 2i*0

0.065

C . Two m i l l i l i t e r s o f c o n c e n tr a te d h y d r o c h lo r ic a c id p e r
l i t e r o f e th a n o l.
G lass
C e ll I I

2 1 ,6 0 0

22,200

22,200

22,200

22,200

1 ,5 1 0

1 ,5 1 0

1 ,5 1 0

1 ,5 1 0

1 ,5 1 0

K m ean = ° - 0 6 0 "

20,000 t o
22,600
1 ,5 1 0

0.066 t o
0.060

° * 0U 5 cm _1

Cs was fo u n d to be n e g l i g i b l e t h e r e f o r e o n ly Rx i s g iv e n ab o v e .

103

Sam ple P r e p a r a t i o n and H a n d lin g P ro c e d u re s
F o r t h e c o n d u c ta n c e work i t was fo u n d n e c e s s a r y t o c a r e f u l l y d i s t i l
th e h a lo g e n f l u o r i d e d i r e c t l y i n t o th e w eighed co n d u ctan ce c e l l .

I f th e

compound was sip h o n e d th ro u g h th e m e ta l l i n e , o r i f th e d i s t i l l a t i o n was
so r a p i d a s t o form a s p r a y , i m p u r i t i e s were in tr o d u c e d i n t o th e c e l l
and h ig h c o n d u c ta n c e v a lu e s w ere o b ta in e d .
The i o d i n e p e n t a f l u o r i d e was sip h o n e d from th e s to r a g e c o n ta in e r
i n t o an a u x i l i a r y tu b e and th e n d i s t i l l e d from th e tu b e i n t o th e c e l l .
Brom ine p e n t a f l u o r i d e was d i s t i l l e d d i r e c t l y from t h e s to r a g e c o n ta in e r
i n t o th e c e l l .

The s e tu p i s i l l u s t r a t e d i n F ig u re 36.
To vacuum l i n e
$

<8>

F ig u re 36.

The M ixing System f o r B rom ine P e n ta f lu o r i d e S o lu tio n s

10k

C h lo r in e t r i f l u o r i d e was d i s t i l l e d d i r e c t l y from a h a l f empty ta n k
s in c e i t was n o t p o s s i b l e t o f r a c t i o n a l l y d i s t i l i t w ith th e equipm ent
u s e d f o r io d in e p e n t a f l u o r i d e and brom ine p e n t a f l u o r i d e .

The c h lo r in e

t r i f l u o r i d e was assum ed t o b e f a i r l y p u r e s in c e i t s c o n d u ctan ce was v e ry
c l o s e t o c o n d u c ta n c e s p r e v i o u s l y r e p o r t e d .

.

F o llo w in g th e a d d i t i o n o f th e h a lo g e n f l u o r i d e th e c e l l was rem oved
from th e l i n e , re w e ig h e d , and r e t u r n e d t o th e l i n e .

The le a d s from th e

c o n d u c ta n c e b r id g e w ere c o n n e c te d , a b a th a t th e d e s ir e d te m p e ra tu re was
p la c e d a ro u n d t h e t u b e , and t h e th erm o c o u p le was i n s e r t e d i n t o th e
th e rm o c o u p le w e l l .

The te m p e r a tu r e - v e r s u s - tim e cu rv e was re c o rd e d b y a

Brown r e c o r d i n g p o t e n t i o m e t e r .

When th e s lo p e became z e ro th e te m p e ra tu re

o f th e i n t e r h a l o g e n was assum ed t o b e th e same as t h a t o f th e b a t h .

The

r e s i s t a n c e o f t h e c e l l was th e n m easu red a t v a r io u s f r e q u e n c ie s by u se
o f th e c o n d u c ta n c e b r i d g e .
The h y d ro g e n f l u o r i d e s o l u t i o n s w ere p re p a re d by c o n d e n sin g hydrogen
f l u o r i d e d i r e c t l y i n t o t h e h a lo g e n f l u o r i d e sam ples p r e p a re d as ab o v e .
The w e ig h in g and c o n d u c ta n c e m e a su rin g p ro c e d u re was r e p e a te d a s ab o v e.
I n t h i s m anner i t was p o s s i b l e to p r e p a r e s e v e r a l hyd ro g en f l u o r i d e s o lu ­
t i o n s from e a c h sam ple o f h a lo g e n f l u o r i d e .
F o r m o st o f t h e s e ru n s th e hydrogen f l u o r i d e was p a s s e d s lo w ly o v e r
c o b a l t i c f l u o r i d e t o remove m o i s t u r e .

M easurem ents o f th e hydrogen

f l u o r i d e c o n d u c ta n c e , h o w ev er, i n d i c a t e d t h a t i t was r a t h e r im pure from
a c o n d u c ta n c e s t a n d p o i n t .

The m ain d i f f i c u l t y ap p e a re d t o be t h a t im­

p u r i t i e s d e s o rb e d from th e s i d e s o f th e p l a s t i c tu b e i n t o th e hydrogen
f lu o rid e .

T h is d i f f i c u l t y was n o t e n c o u n te re d w ith th e h a lo g e n f l u o r i d e s .

105

B ecause o f th e above d i f f i c u l t y v e r y few m easurem ents were made a t e x ­
tre m e ly h ig h h y d ro g e n f l u o r i d e c o n c e n t r a t i o n s .
The te m p e r a tu r e b a t h was m a n u a lly c o n t r o l l e d .

T em p eratu re was re a d

on a c a l i b r a t e d m e rc u ry th e rm o m eter whose s c a le was s u b d iv id e d t o te n th s
of a d eg ree.

F o r th o s e m easurem ents done a t 0° and -7B°C an ic e - w a te r

o r Dry I c e - a c e t o n e b a t h was u s e d .

G e n e r a lly th e te m p e ra tu re was a l t e r ­

n a t e l y r a i s e d and lo w e re d t o d e te rm in e w h eth er th e e f f e c t b e in g m easured
was r e v e r s i b l e .
C.

D a ta and C a lc u l a tio n s

JLn th e f o llo w in g p a g e s th e c o n d u ctan ce d a t a f o r c e r t a i n h a lo g e n
f l u o r i d e s and t h e i r hyd ro g en f l u o r i d e s o l u t i o n s i s p r e s e n te d i n t a b u l a r
and g r a p h i c a l fo rm .

I n f o r m a tio n p e r t a i n i n g t o th e c a l c u l a t i o n o f c e r t a i n

o f th e q u a n t i t i e s p r e s e n te d i n th e t a b l e s i s g iv en h e r e .
The s p e c i f i c c o n d u c ta n c e o f hyd ro g en f l u o r i d e , re c o rd e d as
was o b ta in e d b y s u b t r a c t i n g th e c o n d u c ta n c e o f th e s t a r t i n g s o lv e n t from
t h e s p e c i f i c c o n d u c ta n c e o f th e s o l u t i o n ^L) .

L i s o b ta in e d from th e

e q u a tio n
L = K .

i

R
where K i s t h e c e l l c o n s ta n t d is c u s s e d i n th e p re v io u s s e c t i o n , and R ,
th e t o t a l r e s i s t a n c e o f th e c e l l , i s o b ta in e d by p l o t t i n g Rx v e r s u s th e
i n v e r s e s q u a re r o o t o f th e f re q u e n c y and e x t r a p o l a t i n g to i n f i n i t e
f re q u e n c y .

A c t u a l l y i n many c a s e s R

was found t o be v e ry s m a ll and Rx

a t f o u r th o u s a n d c y c le s p e r seco n d was ta k e n as R .

The s p e c i f i c

106

c ir c u m s ta n c e s u n d e r w hich t h i s was done a r e d is c u s s e d below i n th e t a b l e s
c o n c e rn e d .

Th® p l o t s u s e d to o b ta i n R from R__ a r e d is c u s s e d i n th e

s e c t i o n on th e o r y

ab o v e ) .

I n m ost c a s e s Cg was n e g l i g i b l e and t h e r e f o r e

o n ly Rx was g iv e n .
M o lar c o n d u c ta n c e s o f h y d ro g en f l u o r i d e i n th e s o l u t i o n s were c a lc u ­
l a t e d b y u se o f t h e e q u a tio n
M

ac 1000 Lnliw
r
C

where M is the molar conductance and C is the molarity defined by
C

*

number o f equivalents o f HF
total weight/density

The u n i t s o f M a r e o h m s ^ c m ^ o le s 1 and w i l l n o t be r e p e a te d i n th e t a b l e s
f o llo w in g .
The d e n s i t i e s o f some h a lo g e n f lu o r id e - h y d r o gen f l u o r i d e s o lu t i o n s
w ere d e te rm in e d i n t h i s work and t h e d a ta a re g iv e n i n T a b le XI and
F ig u re 2 7 .
I n some c a s e s t h e c o n d u c ta n c e s o f th e s o lu t i o n s a t te m p e ra tu re s
o t h e r th a n 25°C w ere d e te rm in e d i n o r d e r t o d is c o v e r w hether t h e r e was
any u n u s u a l te m p e r a tu re - c o n d u c ta n c e r e l a t i o n s h i p .

I n th e c a s e o f io d in e

p e n ta f lu o r id e - h y d r o g e n f l u o r i d e s o l u t i o n s th e v a r i a t i o n i n th e te m p e r a tu re co n d u c ta n c e r e l a t i o n s h i p a t v a r io u s c o n c e n tr a tio n s was q u ite s l i g h t and
i n o r d e r t o make th e e f f e c t o b v io u s i t was n e c e s s a r y t o p l o t th e p e r c e n t
change i n c o n d u c ta n c e a t 20°C v e rs u s c o n c e n tr a tio n o f hydrogen f l u o r i d e .
The p e r c e n t ch an g e i n c o n d u c ta n c e a t 20°C was d e te rm in e d f o r each
s o l u t i o n whose c o n d u c ta n c e had b een m easu red a t v a r io u s te m p e r a tu r e s , by
d e te r m in in g th e s lo p e o f p l o t s o f s p e c i f i c co n d u ctan ce v e r s u s te m p e ra tu re
f o r th o s e s o l u t i o n s a t 20°C and th e n u s in g th e e q u a tio n

107

p e r c e n t change a t 20°C = — -^ e f ^99---------- c o n d u c ta n c e a t 20UC
A lth o u g h some s o l u t i o n c o n d u c ta n c e s w ere d e te rm in e d i n ru n A u s in g
th e c o n ta m in a te d io d in e p e n t a f l u o r i d e and i n r u n D u s in g th e c o n ta m in a te d
brom ine p e n t a f l u o r i d e , th e s e have been o m itte d h e re b e c a u se th e c o n ta m i­
n a t i o n r e n d e r e d them m e a n in g le s s .
The p r o b a b le e r r o r f o r e a c h r u n i s p r e s e n te d w ith th e d a ta i n
q u e s ti o n .

O th e r p e r t i n e n t in f o r m a tio n r e g a r d in g e a c h s p e c i f i c t a b l e i s

g iv e n below e a c h t a b l e .
F o r th e c o n d u c ta n c e r u n s a lr e a d y p r e s e n te d th e h y d ro g en f l u o r i d e
from t h e c y l i n d e r was s lo w ly p a s s e d o v e r c o b a l t i c f l u o r i d e t o remove any
m o is tu r e w hich may have b e e n p r e s e n t .

I t was fo u n d , h o w ev er, t h a t th e

co n d u c ta n c e o f t h e h y d ro g en f l u o r i d e was r a t h e r h ig h , , 2-5 x 10
at
O
O
16b
25 C com pared to 1 .5 x 10
a t 15 p r e v io u s ly r e p o r t e d ,
and t h a t i t
d rifte d ra th e r ra p id ly .

A p p a re n tly i m p u r i t i e s d e s o rb in g from th e w a lls

o f th e f lu o r o t h e n e tu b e ca u sed t h i s e f f e c t .
I n o r d e r t o g e t some i d e a o f th e sh ap e o f th e e q u iv a le n t co n d u ctan ce
c u rv e f o r t h e io d in e p e n ta f lu o r id e - h y d r o g e n f l u o r i d e s o l u t i o n s a few
d e te r m in a tio n s w ere made s t a r t i n g w ith hydrogen f l u o r i d e w hich had been
d r ie d o v e r c o b a l t i c f l u o r i d e and s t o r e d i n a new f lu o r o th e n e t u b e .

The

co n d u cta n ce was c h a n g in g w ith tim e d u r in g th e ru n and th e r e s u l t s a re
p ro b a b ly n o t a c c u r a te t o b e t t e r th a n tw e n ty p e r c e n t .

Rx m easurem ents

w ere made a t f o u r th o u s a n d c y c le s o n ly , and th e v a lu e s o f th e s p e c i f i c
c o n d u c ta n c e o f h y d ro g en f l u o r i d e ( L ^ ) were o b ta in e d by s u b tr a c t i n g th e
co n d u c ta n c e o f th e h y d ro g en f l u o r i d e a lo n e from th e m easured co n d u c ta n c e
o f th e s o lu tio n .
The r e s u l t s a r e t a b u l a t e d i n T a b le XXI.

ic y

TABLE XVII
THE SPECIFIC CONDUCTANCE OF IODINE PENTAFLUORIDE AT VARIOUS TEMPERATURES*

T°C

F req u e n c y

booo

20 O0

1000
ohms

boo

R
ohms

6000
6501

6000
650 b

5992
6888

6563
7151
790b
8529

6567
7157
7905
8531

6559
71U0
7893

600

L
X

Run A**

30.1

5993

2 5 .2
2 5 .0

6b91
6562

20.3
15.1
11 .b

71U7
7897
8532

599b
6b98
6563
71b9
7899
8530

5998
6500

6563
7151
7901

8529

8529

2.67
2 .8 7
2 .8 8
2 .2 7
2 .0 1
1 .8 6

-SHSr-K-

Run B

25.8
2 3 .6
1 7 .9

13.0

30320
32250

32250

35200

35270

38750

38775

30350

3O36 O
32280

30370

35310

30365
32300
35320

38800

38820

38830

32310

35320

3O33 O
3223 O
35200
38700

0 .5 3 8
0 .5 1 6
0.1460
0 .lily

27800

0.572
0 . 5I4U
0.898
0.1i87

Run C
2 5 .0

21.9
1 6 .9

15 .b

28020
29290
31820
32730

28080

29380
31880
32790

251bO
29b20
31910
32820

28150
29bb0
31930
32830

28160
29b50
31935
328bO

29200

31800
32700

* Cs was n e g l i g i b l e f o r a l l tn e s e r u n s . The v a lu e s given a re f o r
Rx ( i n ohms) a t th e v a r io u s f r e q u e n c i e s .
-JHt- The i o d i n e p e n t a f l u o r i d e i n t h i s r u n was d i s t i l l e d i n t o t h e c e l l
v e r y r a p i d l y and a p p a r e n tly c a r r i e d o v er some im p u r i tie s .
*** The c e l l c o n s ta n t f o r t h i s r u n was 0 .1 6 3 cm” 1 , th e s l i g h t change
b e in g due to a change i n h e ig h t o f th e i n s u l a t i o n around th e
p la tin u m le a d s o f c e l l I .
-Stshbj- I n t h i s ru n th e a v e ra g e e r r o r f o r R i s '100 ohms , and th e av erag e
e r r o r f o r L i s 0 .0 0 2 X 10”* . T h is e r r o r i s due to e r r a t i c p l o t s
o f Rx v e r s u s 1 / fT* .

109

2.7

2.1

10

20

30

Temperature °C
F igu re 3 7 . S p e c ific conductance as a fu n c tio n o f tem perature
fo r io d in e p e n ta flu o r id e (ru n A) .

110

12

22

16
T e m p e ra tu re

26

o
C

F ig u r e 38 # S p e c i f i c c o n d u c ta n c e a s a f u n c t io n o f te m p e r a tu re f o r
i o d i n e p e n t a f l u o r i d e ( ru n B ) ,

Ill

o MB

15

18

22

25

F ig u r e 3 9 . S p e c i f ic c o n d u c ta n c e a s a f u n c t i o n o f te m p e ra tu re
f o r i o d i n e p e n t a f l u o r i d e ( r u n C) .

112
TABLE m

il

THE SPECIFIC CONDUCTANCES OF BROMINE PENTAFLUOR1DE AND
CHLORINE TRIFLUORIDE AT VARIOUS TEMPERATURES
F re q u e n c y
T°C

"Vobo

2OXf”

^

io o b
60U
k ilo h m s

S66~

X 1 0 “ 3ohms

^
X lO ’ cm"1
o h m s'1

Run D
2 5 .0
1 9 .1
1 2 .2
5 .8

122
13^
137
iia

122
135
138
1U3

122
135
139
1 hh

122
135
139
114

122
136
139
114

122
133
136
139

800

680

625
629
900

5.08
U.73
U.U5
a . 2i

Run E
2 5 .0

736

772

800

790

v

0 .9 1

Run F
2 5 .0
0 .0
60

626
629
900

627

629

630

630

—

...

—

—

—

—

—
—

C h lo rin e T r i f l u o r i d e 3
R
Rx X 10” 6 ohms
X 10" ohms
2 5 .0
‘78

1 2 .8
1 0 .8

—
—

—
—

—
—

—
—

1 2 .8
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0 .9 9 1
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cm"1
U.86
6 .5

The b ro m in e t r i f l u o r i d e f o r t h i s r u n was r a p i d l y d i s t i l l e d , and
p r o b a b ly c o n ta in e d some im p u r ity from th e m e ta l vacuum l i n e .
T h e re i s an e r r o r o f p l u s o r m inus_one th o u sa n d ohms i n R due to
e r r a t i c c u r v e s f o r Rx v e r s u s 1 / \[f . The c o rre s p o n d in g e r r o r in
L i s a b o u t p l u s o r m inus one p e r c e n t .
F o r ru n s B and C th e brom ine p e n t a f l u o r i d e was v e ry c a r e f u l l y
d i s t i l l e d . The e r r o r h e r e i s a b o u t p lu s o r m inus f i v e p e r c e n t due
m a in ly t o t h e u se o f a u x i l i a r y r e s i s t o r s o f d o u b tf u l a c c u r a c y .
The v a lu e a t -60°C i s ap p ro x im a te s in c e th e c e l l c o n s ta n t f o r
-78°C i s u s e d . Where f re q u e n c y v a r i a t i o n i s o m itte d i t i s n eg ­
l i g i b l e com pared t o o t h e r e r r o r s .
The e r r o r a t -78°C i s a p p ro x im a te ly p lu s o r m inus te n p e r c e n t
due t o c e l l c o n s ta n t e r r o r .

113

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115

TABLE XXI
CONDUCTANCES OF IODINE PENTAFLUORINE-HYDROGEN FLUORIDE SOLUTIONS
WITH VERY HIGH HYDROGEN FLUORIDE CONCENTRATIONS*

Grams
IF e

0 .0

C
HF

-----

R ohms
Cat IjDOO c y c le s )

L
ohm s"1cm“ 1
X 10~4

LHF
ohm s"1cm”
X 10*"4

Mo
a t 25 C

5U5

2 .9

-----

-----

l .U

1*8

280

5 .7

2 .8

0 .0 6 3

3 .5

1*5

225

7 .1

h.2

0 .0 9 2

6 .2

hh

205

7 .8

a .9

0 .1 1

* S t a r t i n g w ith 1 5 .0 5 gram s o f hydrogen f l u o r i d e , and m easured a t 25 C .
See p r e v io u s p ag e f o r o t h e r in fo r m a tio n c o n c e rn in g t h i s t a b l e .

116

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117

1.0

P ercent change >
in 1 a t 20°C *

0.0

0

6

12

16

2k

C (m oles per l i t e r )
F igu re lil • P ercen t change in s p e c if ic conductance o f io d in e
p en ta flu o rid e-h yd ro gen flu o r id e s o lu tio n s versu s m olar con­
c e n tr a tio n s o f hydrogen flu o r id e (d a ta from run C1) .

118

TABLE XXII
CONDUCTANCES OF BROMINE PENTAFLUORIDE-HIDROGEN FLUORIDE SOLUTIONS
RUN E»*

T°C

Grams
HF

2 5 .0
0 .0
-60
2 5 .0
o .o
-6 0
2 5 .0
1 5-5
0 .0
2 5 .0

0 .1 9
0 .1 9
0 .1 9
0.1*0
o.i*o
0.1*0
1 .0 5
1 .0 5
1 .0 5
2.25

CHF
a t 25 C
0 .3 2
— - —

o.6U
- —
—

1.61*
—
_ —

3 .3 8

R ohms
a t 1*000
C y cles
1 8 7,000
1 6 2,000
252,000
7 8 ,3 0 0
7 6 ,0 0 0
1 3 0,000
2 6 ,0 5 0
2 6 ,1 0 0
27,5 0 0
8 ,9 0 0

L
l hF
ohms~1cm“ :L ohms-1 cm-1
X 107
X 107
3.3U
3.U3
2 .8
8 .0 5
7 .3 0
5.U 6
2 3 .8
2 3 .5
2 0 ,2
7 0 .0

2.1*3

M
X 104
a t 25°C
7 .6

--------

—

-----

-------

7 . Ill

1 1 .2

- —

-------

— -

-------

2 3 .6

1U.5

-------

--------

—

-------

7 0 .0

20 .7

* T h is r u n was s t a r t e d b y ad d in g h y d ro g en f l u o r i d e t o th e brom ine p e n ta f l u o r i d e u s e d i n r u n E . T h e re was a t o t a l o f 7 7 .0 0 grains o f brom ine
p e n ta flu o rid e in each s o lu tio n .
The c e l l was le a k i n g hy d ro gen f l u o r i d e d u r in g t h i s r u n and t h e r e f o r e
a l l v a lu e s o f c o n d u c ta n c e a t h ig h e r c o n c e n tr a tio n s a re p ro b a b ly lo w .
T h ere i s no way o f e s ti m a t in g th e e r r o r due t o l o s s o f hydrogen
flu o rid e .
T h ere i s a c o n s id e r a b le e r r o r i n th e v a lu e s a t ab o u t -60°C becau se th e
r e a d in g s w ere a c t u a l l y ta k e n as th e l a s t r e s i s t a n c e m easurem ent b e f o r e
th e s o l u t i o n b eg an t o f r e e z e . The e r r o r i s th e r e f o r e due to m aking th e
m easurem ent a t a te m p e r a tu re o th e r th a n t h a t a t wliich th e c e l l was
c a l i b r a t e d ( t h e c a l i b r a t i o n a t -78°C was u se d ) f and a ls o t o th e f a c t
t h a t th e r e a d in g s h ad t o be made r a p i d l y .
R ea d in g s w ere ta k e n a t f o u r th o u sa n d c y c le s o n ly s in c e th e v a r i a t i o n
w ith fre q u e n c y was fo u n d to be v e ry s l i g h t .

119
TABLE XXIII
CONDUCTANCES OF BROMINE PENTAFLUORINE-HYDROGEN FLUORIDE SOLUTIONS
RUN F *

T°C

Grams
HF

CHF
a t 25°C

2 5 .0
0.0
-6 0
2 5 .0
0 .0
25.0
0.0
-60
2 5 .0
0 .0
-60
25.0
0.0
- 60-70
25.0
0.0
- 60-70
2 5 .0
0 .0
- 60-70

0 .2 7
0 .2 7
0 .2 7
0.38
0 .3 8
0 .5 3
0 .5 3
0 .5 3
0 .9 3
0 .9 3
0 .9 3
2 .1 3
2 .1 3
2 .1 3
4 .2 3
4 .2 3
i t . 23
6 .8 6
6 .8 6
6 .8 6

0 .4 3
—

--0.60
—

0.83
—
—
l.U ?
—
—
3 .2 0
—
—$ .9 h
—
—
8 . dk

——
*

R ohms
a t hOuO
c y c le s

103,500
102,700
122,000
60,600
5 9 ,3 0 0
3)4,1400
30,000
8,000
13,7 0 0
12,700

L,ooo
3,000
2,700
liiO O
bho
875
1,000
h96
525
900

L
ohms~1cm 1
X 10 7
5 .9 9
5 .ia
5 .8
1 0 .2
9Sh
1 8 .0
18.8
88
U5
hh
175
190
206
500
739
635
710
1250
1080
780

lhf

ohms” 1cm~ 1
X 107

5.00
—
—
9 .2
—
17 .0
—
—
hh
—
—
190
—
—
738
—
—
1250
—
m
m
+m

M
a t 25°C
X 10 4

11.8
—

—
1 5 .4
--2 0 .5
—
—
30
—
—
60
—
—
125
—
—
15U
—

* T h is r u n was s t a r t e d b y ad d in g h y d ro g en f l u o r i d e t o th e brom ine p e n ta f l u o r i d e i n r u n F . T h e re was a t o t a l o f 7 7 .5 9 grains o f brom ine p e n ta f l u o r i d e i n ea c h s o l u t i o n .
T h e re i s a p o t e n t i a l l y l a r g e e r r o r i n th e v a lu e s f o r th e co n d u c ta n c e s
a t v e ry low te m p e r a tu re s s in c e th e c e l l was c a l i b r a t e d o n ly a t -78 C.
The o v e r - a l l e r r o r s i n t h e c o n d u c ta n c e s a re p ro b a b ly ab o u t f i v e p e r ­
c e n t f o r t h e s o l u t i o n s a t lo w er c o n c e n tr a tio n s b eca u se o f some un­
c e r t a i n t y i n th e v a lu e s f o r th e a u x i l i a r y r e s i s t a n c e s u sed w ith th e
c o n d u c ta n c e b r i d g e . P r e c i s i o n r e s i s t o r s i n th e p ro p e r ran g e were n o t
a v a ila b le .
R e s is ta n c e s w ere m ea su re d a t f o u r th o u sa n d c y c le s o n ly s in c e th e
change w ith f re q u e n c y was s m a ll.

120

12

9

6

3

O
O

2

U

6

8

C a t 25°C
F ig u r e k 2 . S p e c i f i c conduc ta n c e - c o n c e n tr a tio n r e l a t i o n ­
s h i p o f b ro m in e p e n ta flu o rid e -h g rd ro g e n f l u o r i d e s o lu t i o n s
b a s e d upon r u n F f o n ly* A , 25>°C; B , 0°C ; C , -6 0 t o - 70°C .

'IT S

Csl

'LPv

1A
O

XA

vrv

(0
o

M
2:

Figure U3. Holar conductance versus the square root of the m o la rity
of hydrogen fluoride for bromine pentafluoride-hydrogen fluoride s o lu tio n s
at 25°Cs © run
□ run E 1. The points in run E* were d riftin g due
to loss of hydrogen f lu o r i d e .

121

122

TABLE XXIV
CONDUCTANCES OF CHLORINE TKIFLUORIDE-HYDROGEN FLUORIDE SOLUTIONS'*

T°C

2 5 .0
-76
2 5 .0
-78
2 ^ .0
-7 8
25 .0
-78

Grams
HF

C
HI?
a t 2S°C

R ohms
a t 1+000
c y c le s
X 10” 3

L
oluns” 1crn“ 1
X 10 s

lhf

,
-1cm-1
ohms
X HT

H
a t 25 C
X 106

0 .6 2

1 .0

2 ,1 0 0

2 .9 6

2.1+7

2.1+7

0 .6 2

---

1 ,5 3 0

1+.5

—

—

0 .8 +

1.35

960

5.U9

6 .0 0

1+.1+5

7U0

9 .5

—

ll+2

U3.7

1+3.2

85

8 2 .5

—

0 .8 +
1 .6 2
1 .6 2

—

2 .5 7
—

3 .0 5

I+.67

18

350

3 .0 5

—

15

i+OO

350

—

1 6 .8
—

75
—

—

« T h is r u n was s t a r t e d by a d d in g hydrogen f l u o r i d e to th e c h lo r in e t r i ­
f l u o r i d e u s e d f o r th e p u re c h l o r in e t r i f l u o r i d e r u n . T here was a
t o t a l o f £ 6 .0 £ grams o f c h l o r in e t r i f l u o r i d e i n e a c h a d d i t i o n .
The o v e r - a l l e r r o r s i n c o n d u c ta n c e s a re p ro b a b ly a b o u t f i v e p e r c e n t
due t o u n c e r t a i n t y i n th e r e s i s t a n c e v a lu e s f o r th e a u x i l i a r y r e s i s t ­
a n ce s u se d on t h e c o n d u c tan ce b rid g e * P r e c i s i o n r e s i s t o r s in th e
p r o p e r ra n g e w ere n o t a v a i l a b l e .
F o r th e low te m p e r a tu r e m easurem ents t h e r e i s an u n c e r t a i n t y o f te n
p e r c e n t due t o u n c e r t a i n t y i n th e v a lu e f o r th e c e l l c o n s ta n t.
R e s is ta n c e s w ere m easu red a t f o u r th o u sa n d c y c le s o n ly f o r th e same
r e a s o n s m e n tio n e d p r e v i o u s l y .

123

ho

30
L X 10

,7

ohm*' cm

-75 c

20

10

o
0

1

2

3

k

C a t 25°C
F ig u r e hi* • S p e c i f ic c o n d u c ta n c e - c o n c e n tr a tio n r e l a t i o n s h i p s
f o r c h l o r i n e t r i f l u o r i d e - h y d r o gen f l u o r i d e s o lu t i o n s a t two
d i f f e r e n t te m p e r a t u r e s .

6

k

2

O
2 .0

Vc~
F ig u r e lif>. M o lar c o n d u c ta n c e v e r s u s t h e sq u a re r o o t o f
h y d ro g e n f l u o r i d e m o l a r i t y f o r s o l u t i o n s o f h y d ro g en
f l u o r i d e i n c h l o r i n e t r i f l u o r i d e a t 2 $ °0 .

125

D.

D is c u s s io n o f th e R e s u lts

C o n d u ctan c es o f th e H alogen F lu o r id e s
The s p e c i f i c c o n d u c ta n c e s w hich have been d e te rm in e d f o r th e h alo g e n
f l u o r i d e s i n t h i s w ork a r e i n g e n e r a l i n good agreem ent w ith , o r somewhat
lo w e r t h a n , c o n d u c ta n c e s r e p o r t e d p r e v i o u s l y .

In th e fo llo w in g t a b l e th e

r e s u l t s o b ta in e d i n t h i s r e s e a r c h a re com pared w ith th e b e s t p r e v io u s ly
re p o rte d r e s u l t .
TABLE XXV
SPECIFIC CONDUCTANCES OF THE HALOGEN FLUORIDES

Compound

L
B e s t V alue
O b ta in e d H ere
i n ohm s'^cm - 1 a t 25 C

L
B e s t P r e v io u s ly
R e p o rte d V alue
ohms*~1cm”

R eferen ce

5.3 x i c f 6

1 .9 2 X 10'® a t 25°C

12

BrFe

9 .1 X 1 0 " e

19

C1F3

k .9 x 10~9

8 .5 X 10-7 a t ? °C
_9
0
3 X 10
at ? C

13

E m eleu s, W o o lf, and S h a r p e ,20"*22 s u g g e s te d t h a t th e c o n d u c tiv ity o f
io d i n e p e n t a f l u o r i d e i s due t o s e l f - i o n i s a t io n a c c o rd in g to th e e q u i­
l ib r iu m r e a c t i o n
2XFe

= IF 4 +

+

I F S~

T h is a ssu m p tio n i s b a s e d upon r e a c t i o n s s u c h as
SbFB + 1F6

=

U F**)

SbF6” )

126

and
KF

+

IF e

=

K+.[f 6‘

e a c h o f w h ich c a u s e s an i n c r e a s e i n c o n d u c ta n c e ,

i f , how ev er, p o tassiu m

f l u o r i d e i s added t o th e an tim o n y p e n t a f l u o r i d e - i o d i n e p e n ta f lu o r id e
s o l u t i o n a n e u t r a l i z a t i o n r e a c t i o n o f th e ty p e
KlF 6

+

i f 4SbF6

-

KSbFe

+

re s u lts .
i f i t i s p o s s i b l e t o draw an an alo g y betw een io d in e p e n ta f l u o r id e
and b ro m in e p e n t a f l u o r i d e i t would seem t h a t th e c o n d u c tiv ity o f brom ine
p e n t a f l u o r i d e w ould be due to th e e q u ilib r iu m
2BrF6

*

B rF4+

+ B rF 6~

The c o n d u c ta n c e o f brom ine p e n t a f l u o r i d e h a s been fo u n d i n t h i s work
t o v a ry

o n ly s l i g h t l y w ith

te m p e r a tu r e .

P r e v io u s ly i t had

b een r e p o r te d

t o have

a n e g a tiv e te m p e r a tu re c o e f f i c i e n t , however th e p u r i t y

of

th e

m a t e r i a l u s e d p r e v i o u s l y seems to h av e b een somewhat l e s s th a n t h a t ob­
t a i n e d i n t h i s work and i t i s t h e r e f o r e somewhat d o u b tfu l w h eth er th e
r e s u l t s c an be co m p ared .

A s m a ll o r n e g a tiv e te m p e ra tu re c o e f f i c i e n t

m ig h t be assum ed to be due t o th e rm a l i n s t a b i l i t y o f th e io n s i n q u e s tio n .
The c o n d u c ta n c e o f c h l o r in e t r i f l u o r i d e i s so e x tre m e ly low t h a t i t
i s somewhat d o u b t f u l w h e th e r w hat co n d u c ta n c e i t does d e m o n stra te i s
d e p e n d e n t upon a s e l f i o n i z a t i o n , such as t h a t p ro p o se d f o r brom ine t r i ­
f lu o rid e ,
2BrF3

= h rF a+

o r th e p r e s e n c e o f i m p u r i t i e s .

+

BrF4~

I t i s i n t e r e s t i n g t o n o t e , h o w ever, t h a t

c h l o r i n e t r i f l u o r i d e a p p e a rs t o have a n e g a tiv e te m p e ra tu re c o e f f i c i e n t ,
o f c o n d u c ta n c e , a s d oes b ro m in e t r i f l u o r i d e .

127

C o n d u c ta n c es o f H alogen F lu o r id e —H ydrogen
F lu o r id e S o lu tio n s
The c o n d u c ta n c e s o f t h e h y d ro g en f l u o r i d e s o l u t i o n s o f th e h a lo g e n
f l u o r i d e s p r e s e n t a r a t h e r more c o m p lic a te d problem th a n t h a t o f th e
p u re h a lo g e n f l u o r i d e s .

I t c a n be se e n from F ig u r e s hO, h3 and kS t h a t ,

a lth o u g h th e c u rv e s f o r b rom ine p e n t a f l u o r i d e and c h lo r in e t r i f l u o r i d e
a re r a t h e r in c o m p le te , t h e r e i s p ro b a b ly a minimum i n th e m o lar c o n d u c ta n c e - c o n c e n t r a t io n c u rv e f o r e a c h o f th e s e r i e s o f s o lu t i o n s m ea su re d .
T h is i s i n f u l l ag reem en t w ith o th e r work done w ith s o l u t i o n s o f su b ­
s ta n c e s i n n o n -aq u e o u s s o lv e n ts .

The p o s i t i o n o f th e minimum i n t h i s

ty p e o f c u rv e c a n som etim es be e s tim a te d b y u se o f th e e x p r e s s io n 36

m in
w here

i s t h e c o n c e n t r a t i o n a t w hich th e minimum o c c u r s , D i s th e

d i e l e c t r i c c o n s ta n t o f th e medium, and k i s a c o n s ta n t w hich a p p lie d
t o a g iv e n e l e c t r o l y t e i n d i f f e r e n t s o l v e n t s .

U n f o rtu n a te ly th e d i ­

e l e c t r i c c o n s ta n ts o f th e m ix tu re s are n o t known and th e p o s i t i o n o f th e
minimum i s n o t known i n some c a s e s .

The m olar c o n d u c ta n c e s a t th e

minimum c a n b e ro u g h ly a p p ro x im a te d from th e f i g u r e s m e n tio n e d .

The

v a lu e s a re r o u g h ly as fo llo w s *
IF e -hF

3 X 10“ 3

BrFa -HF

7 X 10“ 4

c i f 3- h f

b X 1CT6

The r e a s o n f o r th e o c c u rre n c e o f a minimum i s o b scu re a t b e s t , b u t m ig h t
b e due t o some ty p e o f io n a s s o c i a t i o n .

128

The e q u i v a l e n t c o n d u c ta n c e o f liydrogen f l u o r i d e i n th e s e s o l u t i o n s
o v e r t h e w hole ra n g e o f c o n c e n tr a tio n s m easu red seems to be e x tre m e ly
low and th u s i t a p p e a rs t h a t h y d ro g en f l u o r i d e a c ts as a v e ry weak
e le c tro ly s e .
A n e g a tiv e te m p e r a tu re c o e f f i c i e n t , o r a te n d e n c y to w ard i t , seems
t o be q u i t e g e n e r a l as c a n be s e e n i n F ig u re s U l, h2 and UU.

The m ost

p r o b a b le e x p la n a t i o n i s t h a t th e n e g a tiv e te m p e ra tu re c o e f f i c i e n t i s
a s s o c i a t e d w ith th e rm a l i n s t a b i l i t y o f th e i o n s .
I t i s d i f f i c u l t t o s a y j u s t w hat th e c u r r e n t c a r r y in g s p e c ie s a re
i n t h e s e s o l u t i o n s on th e b a s is o f t h i s w o rk .

On a n a lo g y w ith th e

p o ta s s iu m f l u o r i d e - i o d i n e p e n t a f l u o r i d e sy stem i t m ig h t be assumed t h a t
an e q u ilib r iu m s u c h as
HF

+

IF 6

= H+

+

1F6“

e x i s t s , w h ile an a n a lo g y w ith th e antim ony p e n t a f l u o r i d e - i o d i n e p e n t a ­
f l u o r i d e sy stem m ig h t i n d i c a t e t h a t an e q u ilib r iu m su ch as
HF

+

IF6

=

HF2"

+

IF 4 +

i s m o st im p o r ta n t.
T h is work does n o t p ro v id e any way o f d i f f e r e n t i a t i n g betw een th e
two m ech an ism s.

A s i m i l a r s i t u a t i o n e x i s t s f o r th e brom ine p e n t a f l u o r i d e -

h y d ro g en f l u o r i d e and c h l o r i n e t r i f l u o r i d e - h y d r o g e n f l u o r i d e s y s te m s .

129

V III

MAGNETIC SUSCEPTIBILITIES OF THE HALOGEN FLUORIDES
A. T h e o r e t i c a l A sp e c ts

E very s u b s ta n c e p o s s e s s e s m a g n e tic p r o p e r t i e s t o some d e g r e e .

These

p r o p e r t i e s m a n i f e s t th e m s e lv e s i n one o f th r e e w ays; d ia n a g n e tis m , p a r a ­
m a g n etism , o r fe rro m a g n e tis m .

The g e n e r a l b e h a v io r o f s u b s ta n c e s p o s s e s s ­

in g t h e s e d i f f e r e n t ty p e s o f m agnetism may be d e s c r ib e d as f o llo w s :

if

two m a g n e tic p o le s d e s ig n e d as m^ and ma a re s e p a r a te d by a d is ta n c e r ,
t h e n th e f o r c e b e tw ee n t h e p o le s i s
p
w here th e q u a n t i t y

= Mi m2
a *- r a

i s assum ed t o be e q u a l t o u n i t y i n a vacuum .

q u a n t i t y r e p r e s e n t e d by

The

i s th e m a g n e tic p e r m e a b ility o f th e m edium .

I t i s a m easu re o f t h e te n d e n c y o f th e m a g n e tic l i n e s o f f o r c e to p a s s
th ro u g h th e medium r a t h e r th a n th ro u g h a s u rro u n d in g vacuum.
m a g n e tic s u b s ta n c e s

m-

F or p a ra ­

i s s l i g h t l y g r e a t e r th a n u n i t y , f o r f e rro m a g n e tic

s u b s ta n c e s i t i s much g r e a t e r th a n u n i t y ( o f th e o r d e r o f 103) and f o r
d ia m a g n e tic s u b s ta n c e s i t i s v e ry s l i g h t l y l e s s th a n u n i t y .
I f t h e s t r e n g t h o f th e m a g n e tic f i e l d i s H , th e p r o d u c t

m

H can be

shown86 t o be
/U-K <= k I f I + H
and t h e r e f o r e
^ ^

I
1

-

w here I i s th e i n t e n s i t y o f th e m agnetism in d u c e d by th e f i e l d i n th e
m edium .

V e c to r q u a n t i t i e s a r e d e n o te d by an u n d e r l i n e .

The r e l a t i o n s h i p

130

b etw een H and

i s d e f in e d by

I = KH
where K i s t h e volume s u s c e p t i b i l i t y .
I t h as b e e n fo u n d t h a t i n g e n e r a l th e d ia m a g n e tic s u s c e p t i b i l i t y
o f a s u b s ta n c e i s in d e p e n d e n t o f te m p e ra tu re o r f i e l d s t r e n g t h , w hereas
th e p a ra m a g n e tic s u s c e p t i b i l i t y o f a s u b s ta n c e h a s an in v e r s e te m p e ra tu re
re la tio n s h ip .

F e rro m a g n e tic s u s c e p t i b i l i t i e s v a r y w ith b o th te m p e ra tu re

and f i e l d s t r e n g t h .
The c l a s s i c a l t h e o r y o f diam agnetism i s due t o L angevin,® 7 who
showed t h a t when a m a g n e tic f i e l d i s a p p lie d t o a system o f e l e c t r o n s
m oving a b o u t a n u c le u s t h e r e i s a p r e c e s s io n o f th e e l e c t r o n o r b i t s .
The a n g u la r v e l o c i t y o f th e p r e c e s s io n i s e q u a l to -eH/2mc where e and m
are t h e c h a rg e and m ass o f th e e l e c t r o n and c i s th e v e l o c i t y o f l i g h t .
I t c an a l s o b e shown t h a t th e c l a s s i c a l m a g n e tic moment o f an
e le c tro n in i t s o r b it i s
2
I
2 c
w here <o i s t h e a v e ra g e a n g u la r v e l o c i t y o f th e e l e c t r o n and r ^ i s th e
mean sq u a re r a d i u s o f th e o r b i t p r o je c t e d p e r p e n d ic u la r t o th e f i e l d .
The change i n th e o r b i t a l m a g n e tic moment i n th e f i e l d H due t o th e
su p erim p o se d p r e c e s s i o n i s g iv e n by
M

e rf

( U
2c

e^H

-

eH/mc)

2

e rl
2c

F o r a. sy stem o f n o r b i t s o r ie n te d a t random to th e f i e l d , t h a t i s ,
f o r a s p h e r i c a l l y sy m m e tric a l atom

where r

i s th e m ean s q u a re r a d i u s o f th e o r b i t .

Thus f o r a s p h e r i c a l l y

s y m m e tric a l atom

^

^mc~2

and
w A M,
H

w here 9^

i s th e m o lar s u s c e p t i b i l i t y and i\i i s A v o g ad ro 's num ber.

T h is c l e a r l y shows t h a t t h e m a g n e tic s u s c e p t i b i l i t y o f a d ia m a g n e tic
s u b s ta n c e s h o u ld be in d e p e n d e n t o f te m p e ra tu re and f i e l d s t r e n g t h , t h a t
i t i s n e g a t i v e , and t h a t i t w ould be e x p e c te d t o b e p r e s e n t i n a l l atoms
o r m o le c u le s r e g a r d l e s s o f w h eth er o r n o t th e r e i s a perm anent m ag n etic
moment w hich o vershadow s i t .
The e q u a tio n o b ta in e d above can a ls o be shown to h o ld from a quantum m e c h a n ic a l v ie w p o in t e x c e p t t h a t th e v a lu e o f r 2 i s d i f f e r e n t .

Van V le c k ,6

and P a u lin g ,® 9 have c a l c u l a t e d r 2 and o b ta in e d
r2

1 _ A( A

+ 1) - j

w here n and X a r e th e t o t a l and a z im u th a l quantum numbers a 0 i s th e r a d iu s
o f th e I s o r b i t f o r h y d ro g e n , and ( Z - s ) i s th e e f f e c t i v e n u c le a r c h a r g e .
T h e re i s a ls o a p o s i t i v e term i n th e quantum m e c h a n ic a l e x p r e s s io n w hich
c a n n o t b e e v a lu a te d and w hich i s g e n e r a lly assumed to b e n e g l i g i b l e .
The e x a c t c a l c u l a t i o n o f (Z -s ) i s d i f f i c u l t b u t v a r io u s ap p ro x im ate

132
m ethods have b e e n u s e d t o e s tim a te i t .
and th u s

W. R . Angus60 has d e te rm in e d (Z -s )

f o r a l a r g e number o f atom s o r io n s .

A com parison o f th e

r e s u l t s o b ta in e d h e r e w ith th o s e o b ta in e d by Angus *s method o f a p p ro x i­
m a tio n W ill b e p r e s e n t e d i n s e c t io n V II1 -D .

B.

A p p a ra tu s and Method

The Gouy M agnetic B alan ce
The m a g n e tic s u s c e p t i b i l i t i e s o f th e h a lo g e n f l u o r i d e s w ere d ete rm in e d
b y th e Gouy m e th o d ,6 1 >63

The Gouy m ag n etic b a la n c e u sed i n t h i s work i s

i l l u s t r a t e d i n F ig u re 2*6 and h as b een d e s c r ib e d i n d e t a i l e ls e w h e r e .64
The Gouy m ethod c o n s i s t s e s s e n t i a l l y o f su sp e n d in g a c y l i n d r i c a l sam ple
o f th e m a t e r i a l t o be m easu red b etw e e n th e p o le s o f an e le c tro m a g n e t i n
su c h a m anner t h a t one end o f th e sam ple i s i n a. r e g io n o f uniform h ig h
f i e l d i n t e n s i t y and t h e o th e r end i s i n a r e g io n o f low o r n e g l i g i b l e
f i e l d i n t e n s i t y ; t h e change i n w e ig h t o f th e sam ple when a m ag n etic f i e l d
i s a p p lie d i s m e a s u re d .
The p o le p i e c e s o f th e m agnet i l l u s t r a t e d a re a d ju s ta b le a lo n g t h e i r
common a x i s .

T h e re a re lljiiO t u r n s o f co p p e r w ire aro u n d each p o l e , th e

t o t a l r e s i s t a n c e f o r b o th c o i l s i n s e r i e s b e in g a b o u t f i v e ohms.

Any

c u r r e n t from one t o tw e n ty am peres may be a p p lie d to th e c o i l s .

When

h ig h c u r r e n t s a r e u se d i t i s n e c e s s a r y to c o o l th e co;i.ls by c i r c u l a t i o n
o f o i l th ro u g h th e w in d in g s .
o p e r a t i n g a t 110 v o l t s .

The s o u rc e o f power was a D. C . g e n e r a to r

The c u r r e n t from th e g e n e r a to r was v a r ie d by means

o f s e r i e s r e s i s t o r s and c o u ld be c o n t r o l l e d t o o n e - te n th o f an am p ere.
The change i n w e ig h t o f th e sam ple i s m easured by su sp e n d in g i t i n t o
t h e f i e l d from one arm o f a sem i-m ic ro b a la n c e .

W eight changes as

133

s m a ll as tw o —h u n d re d th s o f a m illig r a m can b e d e te c te d when "this a r r a n g e ­
ment i s u s e d .
The f i e l d s t r e n g t h o f th e m agnet w ith v a r io u s v a lu e s o f a p p lie d
c u r r e n t was d e te rm in e d by m e a su rin g th e change i n w eig h t o f sam ples o f a
s ta n d a r d n i c k e l c h l o r id e s o l u t i o n ^29.20$ n i C l 2 by w e ig h t) .

The f i e l d

s t r e n g t h was c a l c u l a t e d from th e f o llo w in g r e l a t i o n s
i

- ft2)

H3A

=

g Aw

where
ftx = volume s u s c e p t i b i l i t y o f th e l i q u i d
f t3 * volume s u s c e p t i b i l i t y o f

A

= a r e a o f th e t u b e , p a r a l l e l t o th e p o le f a c e s ,
from septum t o r e f e r e n c e m ark; found t o be
1 .88

g
aw

H

a ir

cm 2.

= g r a v i t a t i o n a l c o n s ta n t
* a p p a r e n t change i n w eig h t o f th e sam ple when
p la c e d i n th e f i e l d .
* f i e l d s tre n g th

The r e s u l t s o b ta in e d a re t a b u l a t e d i n T a b le XXVII, and shown g ra p h ic ­
a l l y i n F ig u re 1*8.
The c a l i b r a t i o n o f th e f i e l d s t r e n g t h b y t h i s method i s o n ly a p p ro x i­
m ate s in c e i t assum es t h a t th e s u s c e p t i b i l i t y tu b e c o n ta in s a unifo rm
s a m p le , and t h a t th e septum i s p e r f e c t l y f l a t .

T h is m ethod a c t u a l l y g iv es

a q u a n t i t a t i v e c a l i b r a t i o n o f a p a r t i c u l a r m ag n etic s u s c e p t i b i l i t y tu b e
so t h a t th e e x a c t m a g n e tic s u s c e p t i b i l i t y o f any o th e r m a t e r i a l p la c e d
i n i t may be d e te r m in e d .

u k

The S u s c e p t i b i l i t y Tube
The s u s c e p t i b i l i t y tu b e which was u se d i n t h i s work i s i l l u s t r a t e d
i n F ig u re 5 3 .

I t was c o n s tr u c te d e n t i r e l y o f V y co rV t o r e s i s t th e c o r ­

r o s i v e a c t i o n o f th e h a lo g e n f l u o r i d e s .

The tu b e i s a d o u b le o r

com pensated tub© w ith t h e h a lv e s s e p a r a te d by a sep tu m .

T h is red u ced

th e change o f w e ig h t o f th e tu b e i t s e l f i n th e f i e l d to n e a r ly z e r o .
C o r r e c tio n v a lu e s f o r t h e empty tu b e a re g iv en i n T a b le XXVI.
The tu b e was r e c a l i b r a t e d a f t e r e a c h ru n t o c o r r e c t f o r th e c o r r o ­
s iv e a c t i o n o f t h e compounds u s e d .
are f o r th e i n i t i a l c a l i b r a t io n .

The c a l i b r a t i o n d a t a m en tio n ed above
S u b seq u en t c a l i b r a t i o n d a ta were

e s s e n t i a l l y t h e sam e.
F o r e a c h c a l i b r a t i o n t h e tu b e was f i l l e d t o a s p e c i f i c r e f e r e n c e
m ark a b o u t f o u r in c h e s above th e se p tu m .

When th e s u s c e p t i b i l i t y o f th e

h a lo g e n f l u o r i d e s was d e te r m in e d , h o w ev er, th e tu b e was f i l l e d above th e
m ark s in c e i t i s v e ry d i f f i c u l t t o t r a n s f e r an e x a c t q u a n ti ty o f h alo g en
flu o rid e .

T h is d id n o t m a t e r i a l l y e f f e c t th e r e s u l t s b ecau se th e f i e l d

s t r e n g t h a t t h a t p o i n t was n e g l i g i b l e and th e d e n s i t i e s o f th e s u b s ta n c e s
were known.
Sample P r e p a r a t io n and P ro c e d u re s
I t was fo u n d t h a t th e h a lo g e n f l u o r i d e s c o u ld n o t be d i s t i l l e d
d i r e c t l y from th e m e ta l vacuum l i n e i n t o th e m ag n etic s u s c e p t i b i l i t y tu b e

* C o rn in g G la ss C o.

135

w ith o u t i n t r o d u c i n g m in u te <3uaj* t i t i e s o f p a ra m a g n e tic m a t e r i a l .

F or

t h i s r e a s o n th e s m a ll V ycor a p p a ra tu s i l l u s t r a t e d i n F ig u re 1+7 was con­
s tru c te d .

The h a lo g e n f l u o r i d e s were d i s t i l l e d o r sip h o n ed d i r e c t l y

from th e s to r a g e c o n t a i n e r s i n t o th e a p p a ra tu s i l l u s t r a t e d and d i s t i l l e d
from t h e r e i n t o t h e s u s c e p t i b i l i t y t u b e .
I n th e c a s e o f brom ine t r i f l u o r i d e a sam ple was d i s t i l l e d d i r e c t l y
from t h e ta n k i n t o an aluminum tu b e on th e vacuum l i n e and th e n r e d i s ­
t i l l e d from th e aluminum tu b e t o th e Vycor a p p a r a tu s .
th e n r e d i s t i l l e d I n t o th e s u s c e p t i b i l i t y t u b e .

The sam ple was

The brom ine t r i f l u o r i d e

th u s o b ta in e d was p r o b a b ly c o n ta m in a te d w ith brom ine m o n o flu o rid e s in c e
th e sam ple had a b ro w n ish c o l o r .

A s m a ll amount o f c o n ta m in a tio n w ith a

d ia m a g n e tic s u b s t a n c e , h o w ev er, would n o t m a t e r i a l l y a f f e c t th e r e s u l t
o f t h e m e a su re m e n t.

The e l i m i n a tio n o f p a ra m a g n e tic o r fe rro m a g n e tic

m e t a l l i c s a l t s was a c c o m p lish e d by t h i s p r o c e d u r e .

The c o n s ta n c y ob­

s e rv e d f o r th e s u s c e p t i b i l i t i e s o f a g iv e n s u b s ta n c e a t d i f f e r e n t f i e l d
s t r e n g t h s showed t h a t f e rr o m a g n e tic m a t e r ia ls were a b s e n t.
S u s c e p t i b i l i t y m easu rem ents w ere made on e a c h s u b s ta n c e a t

H f

15 and 20 a m p e re s, c o r re s p o n d in g t o a ra n g e i n f i e l d s t r e n g t h from UOOO
t o 1 2 ,0 0 0 O e r s te d s .
A f t e r e a c h sam ple had b e e n m easured th e r e s i d u a l m agnetism o f th e
p o le p i e c e s was rem oved b y s lo w ly re d u c in g th e c u r r e n t and r e p e a t e d ly
r e v e r s i n g i t s d i r e c t i o n by m eans o f a r e v e r s i n g s w itc h .

136

t—

F igu re 1*6.

The Qcmy magnetic b a la n ce.

137
To vacuum lin e

e and rubber
bands

To balance

Gold ch ain

[Copper
wire

Septum

D i s t i l l i n g apparatus w ith
s u s c e p t ib ilit y tube attached

S u s c e p t ib ilit y
Tube as su s­
pended from
balance

F igure hi • Diagram o f th e Vycor s u s c e p t ib ilit y tube and
d i s t i l l i n g apparatus*

13d
TABLE XXVJ.
APPARENT WEIGHT CHANGES FOR THE EMPTY SUSCEPTIBILITY TUBE
— CALIBRATION I -

C u rren t
Amp.

W eight
(gm)

0

15.26255

5

1 5 . 2621*7

- 0 .0 0 0 0 8

8

15.26235

0 .0 0 0 2 0

11

15.26217

0 .0 0 0 3 0

15

15.26205

0 .0 0 0 5 0

20

1 5 .2 6181*

0 .0 0 0 7 0

A W eight
Cgm)

TABLE XXVII
FIRST CALIBRATION OF THE SUSCEPTIBILITY TUBE WITH NICKEL CHLORIDE

C u rre n t
Amp.

W eight
Cgm.)

A W eight
C o rr.

.*

H calc
O e rs te d s

H
O e rs te d s

0

17 .83925

5

17.86585

0.0267

1*770

1*780

8

17 .90310

0 . 061*1

7325

7360

11

17.93580

0 . 0961 *

9080

9060

15

17.96825

0.1295

10500

101*70

20

17.9973

0.1587

11600

—

# U n p u b lish e d w ork o f R o b e rt E . V&nder Vennen

139

12000

2*000
10

o

15

Amperes
F ig u r e 1*8,

C a l i b r a t i o n c u rv e f o r t h e Gouy b a la n c e .

20

liiO

C.

D ata and C a l c u la tio n s

I n t h e f o llo w in g p a g e s th e m a g n e tic s u s c e p t i b i l i t y d a ta f o r c e r t a i n
h a lo g e n f l u o r i d e s w i l l b e p r e s e n te d i n t a b u l a r fo rm .

In fo r m a tio n p e r ­

t a i n i n g t o t h e c a l c u l a t i o n o f c e r t a i n o f th e t a b u l a t e d q u a n t i t i e s w i l l
be p re s e n te d f i r s t .

The m a g n e tic s u s c e p t i b i l i t y o f a s u b s ta n c e may be

d e te rm in e d w ith o u t a know ledge o f H by a r e l a t i v e m eth o d .

The a p p a re n t

c h a n g es i n w e ig h t o f b o th a s u b s ta n c e o f known, and o f unknown s u s c e p t i ­
b i l i t y a re m e a su re d u s in g t h e same v a lu e s o f c u r r e n t , and th e same s u s ­
c e p t i b i l i t y tu b e .
From t h e r e l a t i o n g iv e n on p ag e
H2 *

2g

Aw

Ki " K2
Thus f o r two s u b s t a n c e s , one o f known m a g n etic s u s c e p t i b i l i t y , and one o f
unknown m a g n e tic s u s c e p t i b i l i t y , whose a p p a re n t w e ig h t change h as b e e n
m ea su re d a t th e same f i e l d s t r e n g t h
_
*

*1 - Ka
K,

2g Awx
Kx - Ka

=

t f X

-

Ka)

+

Ka

AWX
w here Kx , K3 , g , and

have b e e n d e f in e d p r e v i o u s l y , Kx i s th e volume

s u s c e p t i b i l i t y o f th e unknown, and

a p p a re n t change i n w e ig h t

o f th e unknown when p l a c e d i n t h e m a g n etic f i e l d .
The s p e c i f i c s u s c e p t i b i l i t y o f th e unknown {
volum e s u s c e p t i b i l i t y d iv id e d by th e d e n s i t y .
th e se c a lc u la tio n s i s th e re fo re

)

i s d e f in e d as th e

The f i n a l e q u a tio n u s e d i n

where X w i s t h e gram s u s c e p t i b i l i t y .

M olar s u s c e p t i b i l i t i e s ( %

a re

c a l c u l a t e d by m u l t i p l y i n g th e s p e c i f i c s u s c e p t i b i l i t y by th e m o le c u la r
w e ig h t o f t h e s u b s t a n c e .
A ll

aw

v a lu e s g iv e n a r e c o r r e c t e d f o r th e a p p a r e n t change i n

w e ig h t o f t h e s u s c e p t i b i l i t y tu b e when p la c e d i n th e m a g n etic f i e l d .
I n t h e f o llo w in g t a b u l a t i o n o f r e s u l t s th e f i r s t c a l i b r a t i o n h a s
b e e n o m itte d s in c e i t h a s a lr e a d y b e e n p r e s e n te d i n th e p re v io u s s e c t i o n .

1U2

TABLE XXVIII
THE MAGNETIC SUSCEPTIBILITY OF IODINE PENTAFLUOftIDE AT 25°C

C u rren t
Amperes

W eight
Grams

^ w ( c o r r e c te d )
Grams

X v x

10®

0 .0

2 1 . 351*20

5 .0

2 1 .35220

-0 .0 0 1 9 2

-0 .2 6 6

8 .0

21.31*91*5

o.ooi+55

0 .2 6 2

1 1 .0

21.31*695

0 .00695

0 .2 6 5

1 5 .0

21.31*1*55

0.00915

0 .2 6 1

2 0 .0

21.31*21*5

0.0 1 1 0 5

0 .2 5 7

A verage % w = -0 .2 6 2 X 10"®
A verage d e v ia t io n = 0 .0 0 3 X 10

_6

X M = - 5 8 .1 X 1 0 - 6
The d e n s i t y a t 25°C was ta k e n t o be 3 ,1 9 g?n. p e r c c . 18b

1h j

TABLE XXIX
THE MAGNETIC SUSCEPTIBILITY OF BROMINE PENTAFLUGRIDE AT 25°C*

C u rren t
Amperes

W eight
Grams

c o r r e c te d )
Grams

"X w x 106

0 .0

2 1 .50600

5 .0

2 1 . 501+50

- 0 .0011+2

- 0 .2 5 6

6 .0

2 1 . 502U0

0 .0031+1+

0 .2 5 7

1 1 .0

2 1 .5 0 0 5 0

0 .0 0 5 2 6

0 .2 5 9

1 5 .0

21.1+9870

0 .00699

0 .2 5 6

2 0 .0

21.1+9705

0 .0 0 6 6 1

0 .2 6 0

A verage

^

* - 0 .258 X 1 0 “

A verage d e v ia tio n = 0 .0 0 1 X 10

•v
A

h

_6

= -ii5 .1 X 106

■K" The c a l i b r a t i o n d a t a on th e f o llo w in g ps-ge was u sed f o r t h i s r u n .
The d e n s i t y a t 25°C was ta k e n as 2 .hi gm. p e r c c . 16b

lUi

TABLE XXX
apparent weight changes for t h e m p t y s u s c e p t ib il it y tube

FOR THE SECOND CALIBRATION

C u rren t
Amperes

W eight
Grams

0 .0

16.2*8971

5 .0

16.1*8963

-0 .0 0 0 0 8

8 .0

16.1*8955

0 .0 0 0 1 6

1 1 .0

16.1*891*7

0 .00021*

1 5 .0

1 6 . 1*891*0

0 .0 0 0 3 1

2 0 .0

16.1*8937

0.000314

^ w
Grams

TABLE XXXI
SECOND CALIBRATION OF THE SUSCEPTIBILITY TUBE
WliH NICKEL CHLORIDE

C u rre n t
Amperes

W eight
Grams

1 c o r r e c te d )
Grams

H c a lc .
O e rste d s

H*
O e rste d s

0 .0

19.01*710

5 .0

1 9 .0 7 3 3 5

0 .0 2 6 3

U7U5

1*780

8 .0

1 9 .1 1 0 3 0

0 .063I*

7380

7360

1 1 .0

19.11431

0 .0 9 6 0

9060

9060

1 5 .0

1 9 . 171+9

0 .1 2 8 1

101*80

101*70

2 0 .0

1 9 .2 0 3 5

0 .1 5 6 7

11610

----

lh $

TABLE XXXII
THE MAGNETIC SUSCEPTIBILITY OF CHLORINE TRIFLUORIDE AT 30°C

C u rren t
Ajnperes

W eight
Grams

0 .0

2 1 .01*250

5 .0

21.01*130

-0 .0 0 1 1 2

-0 .2 7 2

8 .0

2 1 .0391*7

0 .0 0 2 8 7

0 .2 8 9

1 1 .0

2 1 .0379$

0 .001*31

0.281*

1 5 .0

21.0361*5

0.00571*

0 .2 8 6

2 0 .0

21.03515

0.0 0 7 0 1

0.2 8 7

A verage

-V
A* W =

- 0 .2 8 6 X 10“ 6

Aw ^ c o r r e c te d )
Grams

X 106

(5 am pere ru n o m itte d ) •

A verage d e v i a t i o n ** 0 .0 0 2 X 10“ 6
-26.1* X 10*e
The d e n s i t y a t 30°C i s ta k e n as 1 .8 0 gm p e r c c . 1613

116

TABLE XXXIXI
APPARENT WEIGHT CHANGES FOR THE EMPTY SUSCEPTIBILITY TUBE
FOR THIRD CALIBRATION

C u rre n t
Amperes

W eight
Grams

0 .0

16.^2760

5 .0

16.U2750

-0 .00010

8 .0

1 6 .U27U0

0 .0 0 0 2 0

1 1 .0

I6 .li2 7 3 0

0.00030

1 5 .0

1 6 .1*2720

0 .0001*0

2 0 .0

16.U2710

0 .0 0 0 5 0

^ w
Grams

TABLE XXXIV
V

THIRD CALIBRATION OF THE SUSCEPTIBILITY TUBE
WITH NICKEL CHLORIDE

scxt? ^ c o r r e c te d )
Grams

H e a le .
O e rs te d s

H1
O e rs te d s

C u rren t
Amperes

W eight
Grams

0 .0

1 9 .0 1 7 2 5

5 .0

19.010*1

- 0.0268

U770

U780

8 .0

19.0610

0.0 6 3 7

736u

7360

1 1 .0

1 9 .1 1 3 7

0 .0 9 6 5

9080

9060

1 5 .0

19.11x65

0 .1 2 9 3

10300

10L70

2 0 . 0

1 9 .1 7 5 3

0 .1 5 8 1

11600

TABLE XXXV
THE MAGNETIC SUSCEPTIBILITY OF BROMINE TRIFLUORIUE AT 2Q°0

C u rren t
Amperes

W eight
Grams

0 .0

2 1 .2 9 0 6 0

5 .0

2 1 .2 8 8 8 0

-0 .00170

-0 .2 6 7

8 .0

21.2 8 6 6 0

0.00380

0.250

1 1 .0

21.281+65

0 .0 0 5 6 5

0.2+ 6

i5 .o

2 1 .2 8 2 7 0

0.00730

0.236

2 0 .0

2 1 .2 8 1 0 0

0.00910

0.21l0

A verage 'JC w

=

-0.21+8 X 10“ 6

A verage d e v ia tio n = 0 .0 1 0 X 10
^

%

(c o rre c te d )
Grams

—6

M = - 3 3 .9 X 10”6

The d e n s i t y a t 28°C i s ta k e n as 2 .7 9 grains p e r c c . ^

■W

X IO6

1 Lb

D.

D is c u s s io n o f th e R e s u lts

The p r e d i c t i o n o f m a g n e tic s u s c e p t i b i l i t i e s h as m et w ith v a ry in g
d e g re e s o f s u c c e s s d e p en d in g upon th e m ethod w hich h as oeen u s e d .
P ascal

d e v is e d an e m p ir ic a l t a b l e o f ato m ic m ag n etic s u s c e p t i b i l i t i e s

freon e x p e r im e n ta l d a t a f o r o r g a n ic com pounds.

H is t a b l e s have p ro v en

to be q u i t e s u c c e s s f u l i n p r e d i c t i n g th e s u s c e p t i b i l i t i e s o f m ost o rg a n ic
compounds b u t n o t th o s e o f in o r g a n ic com pounds.

The m ost s u c c e s s f u l

t r e a t m e n t o f t h i s problem from a t h e o r e t i c a l p o i n t o f v iew i s due to
A ngus60 who c a l c u l a t e d a s e t o f io n ic s u s c e p t i b i l i t i e s .
I n t h i s w ork we a r e i n t e r e s t e d i n Angus*s i o n i c s u s c e p t i b i l i t i e s
fo r Cl

Br

, h r* 6 , I* 8

F \

h i s v a lu e s f o r - ^ ^ X 106 a r e 8 .3 9 ,

1 7 .6 7 , 1 1 . 8U, 2 2 .1 7 , and 7 .2 5 , r e s p e c t i v e l y .

The t a b l e on th e f o llo w ­

in g p ag e shows a c o m p ariso n betw een th e e x p e r im e n ta l and c a l c u l a t e d
m a g n e tic s u s c e p t i b i l i t i e s f o r th e compounds whose s u s c e p t i b i l i t i e s were
d e te rm in e d h e re and f o r a few o th e r l i q u i d f l u o r i d e s .
T h e re i s an a p p r e c ia b le d if f e r e n c e b etw een th e c a l c u l a t e d and e x p e ri
m e n ta l v a l u e s .

T h is i s n o t s u r p r i s i n g when one c o n s id e r s t h a t th e c a lc u ­

l a t i o n s a r e b a s e d upon th e a ssu m p tio n t h a t th e a c t u a l io n s m en tio n ed do
e x is t.

S in c e th e compounds l i s t e d a re u n d o u b te d ly c o v a le n t i n c h a r a c te r

t h i s a s su m p tio n w ould c a u se some e r r o r .

Angus has shown t h a t h i s v a lu e s

w i l l g e n e r a l l y p r e d i c t th e m a g n e tic s u s c e p t i b i l i t y o f io n ic compounds
v e ry a c c u r a t e l y .

I t i s a l s o p o s s i b l e t h a t th e p o s i t i v e term o f th e

quantum m e c h a n ic a l e q u a tio n i s n o t n e g l i g i b l e i n th e s e c a s e s and con­
t r i b u t e s t o th e d i f f e r e n c e s betw een th e c a l c u l a t e d and e x p e r im e n ta l
v a lu e s .

1 19

TABLE XXXVI
MAGNETIC SUSCEPTIBILITIES FOE SOME LIQUID FLUORIDES

%

Compound
O bserved
sf6

x 106

C a lc u la te d
-w

SeF6

-51*

-51

TeF6

-66»

-61

MoF6

-26*'

wf 6

-liO»

-6 6

g if3

-2 6

-3 0

BrFa

-3U

-39

BrFB

-U5

-55

-58

-6 6

* R e fe re n c e

62

150

IX

SUMMARY

P ro c e d u re 3 eq u ip m en t^ and "techniques f o r h a n d lin g th e h a lo g e n
f l u o r i d e s and t h e i r h y d ro g en f l u o r i d e s o l u t i o n s y and f o r m e a su rin g t h e i r
vapor p re s s u re s

f r e e z i n g p o i n t s y a p p a re n t m o la l volum es9 c o n d u c t i v i t i e s

and m a g n e tic s u s c e p t i b i l i t i e s , have b een d e v e lo p e d and a re d e s c r ib e d in
d e ta il.
New v a lu e s were o b ta in e d f o r th e c o n d u c t i v i t i e s and f r e e z i n g p o in ts
o f c e r t a i n r e l a t i v e l y p u re h a lo g e n f l u o r i d e s .

The p u r i t i e s were e s t i ­

m ated from t h e c o o lin g c u rv e s o b ta in e d .
The v a p o r p r e s s u r e c u rv e s f o r th e hydrogen f l u o r i d e s o l u t i o n s o f
i o d i n e p e n t a f l u o r i d e , brom ine p e n t a f l u o r i d e and c h l o r in e t r i f l u o r i d e were
d e te rm in e d and th e te m p e ra tu re v a r i a t i o n o f th e p o s i t i v e d e v ia tio n from
R a o u l t 's law i s i n t e r p r e t e d i n term s o f v a r io u s p r o c e s s e s w hich m ig h t
o c c u r i n th e l i q u i d p h a s e .
P h ase d iag ram s f o r th e sy stem s io d in e p e n ta f lu o r id e - h y d r o g e n f l u o r i d e
and brom ine p e n ta f lu o r id e - h y d r o g e n f l u o r i d e were o b ta in e d ,

f iu te c tic p o in ts

w ere o b s e rv e d i n t h e r e g i o n o f h ig h hydrogen f l u o r i d e c o n c e n tr a tio n i n b o th
cases .

D i s c o n t i n u i t i e s i n th e f r e e z i n g p o i n t c u rv e s a re d is c u s s e d i n term s

o f p o s s i b l e s o l i d - s t a t e t r a n s i t i o n s and u n s ta b le compound f o rm a tio n .
The a p p a r e n t m o la l volum es o f some o f th e s o l u t i o n s were m easured
and fo u n d t o be s l i g h t l y s m a lle r th a n w ould be e x p e c te d i f th e s o lu t io n s
w ere i d e a l .

A more open s t r u c t u r e i n th e p u re l i q u i d s th a n i n th e s o lu ­

t i o n s i s p o s t u l a t e d t o e x p l a i n th e s e o b s e r v a tio n s .

151

C o n d u ctan ce m easu rem en ts o f th e Iiydrogen f l u o r i d e s o l u t i o n s o f
s e v e r a l h a lo g e n f l u o r i d e s w ere made a t v a r io u s te m p e r a tu r e s .

The d a ta

o b ta in e d i n d i c a t e d t h a t h y d ro g en f l u o r i d e a c ts as an e x tre m e ly weak
e l e c t r o l y t e i n s o l u t i o n w ith th e h a lo g e n f l u o r i d e s and t h a t th e c o n d u c t­
in g s p e c i e s a r e th e r m a lly u n s t a b l e .
The m a g n e tic s u s c e p t i b i l i t i e s o f s e v e r a l o f th e p u re h alo g en
f l u o r i d e s w ere m ea su red and com pared to v a lu e s p r e d i c te d by A ngus.

The

o b s e rv e d v a lu e s a r e , i n g e n e r a l, lo w e r th a n c a l c u l a t e d , th e d e v ia tio n s
becom ing l a r g e r th e h e a v ie r th e m o le c u le s .

T h is was t o b e e x p e c te d

s in c e t h e c a l c u l a t i o n s a r e b a s e d upon an io n i c m o d el.

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