THE MEASUREMENT OF THE THICKNESS

0F ELECTROLYTIC CHROMIUM WITH
THE RECORDING INTERFEROMETER

THESIS FOR THE DEGREE OF M, S.

Roger CIark Dawes
1932

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m WT 0? THE THICUESS 0F ELECTROLYTIC CHROHIUH
WITH THE RECORDING INTERFEROMETER.

A THESIS

SUBMIT'LED T0 m FACULTY
OF
MICHIGAN STATE COLLEGE
LS
PARTIAL FULFILIMENT OF THE
REQUIREMENTS FOR m DEGREE
0F
MASTER OF SCIENCE

BY

ROGER CLARK DAWES

JUNE 1932

LGKHOWEEDGMENT

To Doctor Dwight Tarbell Ewing for his aid and suggestions
in the overcoming of the obstacles encountered in the work.
to Doctor Clark Wells Chamberlain for the use of his
"Recording Interferometer" and his many suggestions as to

its most accurate use.

95465

IIBEE OF CONTENTS

- Considerations
Introduction
Aymaratus
Experimental Procedure
Data

Conclusions

Bibliographies

Page
Page
Page
Page
Page
Page
Page

1
3
10
13
21

49

C O N S I D E R A T I O N S

The purpose of this problem.was to find, by the use
of a very accurate measuring device, the thickness of
electrolytic chromium at various points on a block of flat
plated steel. .

The steel used in this investigation was made as
nearly optically flat as possible, to aid in the measure-
ment of the various points. A steel surface is not satis-
factory to plate the chromium upon because of the labor
involved in obtaining a smooth and highly polished surface.
To overcome these objections, the block of steel was plated
with alternate plates of copper and nickel. The nickel was
made the outer plate. This nickel was very highly polished.
as invisible scratches on the nickel show up markedly on
the chromium plate. For the conditions of the problem
the nickel plate was worked down Optically flat. The block
was then ready to be plated with the chromium, the thick-
ness of’which was measured with the recording interferometer
designed by Doctor Chamberlain.

The plunger of the interferometer was let down at
a point on the chromium plate. ‘A series of readings were
obtained and a mean taken of the number of bands present in

the field of view. Then the plunger was raised until it

was possible, by protecting the plunger with a glass plate.
to take off the chromium plate with a wad of cotton wetted
with hydrochloric acid. After cleaning off the acid thorough-
1y. the plunger was let down at exactly the same point, and
the number of bands in the field of view were observed.
The difference represented, when multiplied by the correct
factor. the thickness of the chromium plate at the point.

The temperature effect was taken into account, as
with such small measurements, this would be large in
amount.

The specimen. with the optically flat surface up-
#

wards, was placed on the platform of the interferometer
with a firm twisting motion. This was done to exclude as
much air as possible between the specimen and the platform.
According to the work of Doctor Chamberlain (Phys. Rev..§;,
170 (1910).) the air film would have a constant thickness.
The bath in which the plating was done had parallel
sides so as to give a uniform cross-section of the plating
bath all the way from.the anode to the cathode. Also the

specimen was lacquered at all points except where the plate

was desired, so as to give no stray eddy currents.

# The word platfomm is used throughout this thesis.
to designate the part of the interferometer on which the

block was placed to be measured.

I N T R O D U’C T I OiN

In 1901 W. Pfanhauser, Jr., (Z. Electrochem.'1, 895
(1901).) stated a relation between conductivity. cathode
potentials and current distribution. He was the first to
make any statement regarding the fundamentals of throwing
power. In 1922 the following statements were made in the
work of’Kurt Arndt and Oskar Clemens (Chem. Ztg. fig, 925
(1922). ). It was the first published work on the factors
affecting the throwing power of solutions.

”There are two resistances Opposing the flow of
current, one, the ohmic of the bath and the other. an
electrode surface resistance. When the plating begins the
tendency is toward more deposition on the parts nearest the
anode, but this decreases the ion concentration near those
parts and gives rise to a concentration polarization that
diminishes the current there. Relatively more current can
then flow to those parts farther away from the anbde. This
viewpoint leads to the conclusion that the throwing power
will increase the fewer metal ions there are in solution to
begin with and the better the bath.conducts; for with in-
creasing conduction the differences in the resistance of
the different paths becomes less.” Also the throwing power
is influenced by the temperature as well as by the agitation
of the plating bath. That is to say the higher the temper-

ature or the greater the agitation the less is the throwing
power of the given bath.

'Horsch and Fuwa (Trans. Am. Electrochem. Soc.‘gl,
363 (1922).) made a study of the throwing power of four
different zinc plating baths. which resulted in the develop-
ment of a plating bath of high throwing power. Their
statements were to the effect, that in order to have a bath
of high throwing power, it was necessary to have in solu~
tion a large number of conducting ions and to have a rela-
tively small number of free metal ions plated out. To
accomplish this, salts which are slightly ionized or fans
complex ions with the metal ions present are used. In this
type of a plating solution, polarisation will take place
very readily.

In their work the following statement regarding
their calculations may be found: '--, simple calculations
give, (I) the current efficiency of the three cathode
plates as a whole, and (2) the throwing power. eXpressed in
terms of the percentage of the total theoretical weight of
zinc deposited on the three plates, which was deposited
upon each of the three plates at varying distances from the

anode.o--.'

A ---

 

 

ILLUSTRATION OF THROWING POWER #

Anode [C -- Cathode
unit area of the cathode nearest the anode.

unit area of the cathode farthest from the anode.
effective resistance through the solution from the

anode to n.

-~KR£ -- effective resistance through the solution

from.the anode to f; where Kiis any definite
numerical factor, such as 2, 5, etc.

current density at n. I

current density at f.

cathode single potential at n.

cathode single potential at f.

potential drOp through solution only, from anode to n.

potential drOp through solution only. from anode to f.

Current Distribution and Throwing Power -Haring and.Blum.

Trans. Am. Electrochem. Soc. g, 317 (1923).

The anode and cathode are both good conductors as
compared to the bath and we can assume that all points of
the anode and cathode are at the same potential.

It is possible to measure directly during the
electrolysis the following:

(1) The potential of the anode against the solu-
tion, which is conventionally expressed as having the same
sign as the potential that must be applied to cause the
anode to go into solution. This. of course. includes the
static potential and the potential due to polarization.

(2) The potential drop through the solution which
is expressed with the sign indicating the flow of a positive
current.

(3) The potential of the cathode against the solu-
tion, which is equal to the static potential, minus the
potential due to polarization.

From.the same article as mentioned in the footnote
on the preceding page, the following equations were obtain-
ed:

During electrolysis the total potential dr0ps be-
tween the anode and the two points on the cathode are equal

to each.other, that is,

.e+e «- En 2 e - Ef - cf (1)

If the anode potential ea is uniform. it may be eliminated

and therefore.

 

but En : Ian (5)
and Er .-.- 11.1:f . IfKRn (4)
Ian - en : IfKRn - er (5)
.—£5r-IK — e - e
If ‘ 4—— ”
IfRn (6)
I 2K -e - e
n 2 f n (7)
If
lf/K
In'
: K (1 - e1, - en )
f n" ' ' (8)
, f
The metal ratio 1! I D
n _. n n (9)

 

If ‘Ifo

In/If is the ratio of the current densities at 'n'
and 'f'. and is therefore a measure of the current distri-
bution. As above defined. Kiis a measure of the primary

current distribution.
From equation (8). if the cathode efficienOes at

I'n" and 'f' are equal and T'is the throwing power.

T 3 100 (9 0 e ) (10)

..1LEETIL.

If however the cathode efficiences at 'n' and “f“

are not equal, it may be shown that,

 

T=lOO(l-Dn(l-ef-cn)) (11)
'15; s,

where Dh_/'Df is the ratio of the cathode efficiences at 'n'
and 'f'.

Haring (Trans. Am. Electrochem. Soc. 39, 10? (1924)
found that the chief factor in throwing power in nickel
plating is the cathode efficiency. This is for the most
part determined by the ratio of the effective nickel and
hydrogen ion concentrations in the cathode film. All
conditions which increase this ratio improve the throwing

power according to his experiments.

The other works read were more or less of a repi-
tition of the above ideas. Work on throwing power of
chromium was carried out at washington University,- Stout
and Carol (Ind. Eng. Chem. 22, 1324 (1930). The results

were meaningless as far as this work is concerned.

- 10 -

5.? P A R A T U‘S A.N D M A.T E R I‘A L S

A.steel block obtained from the Reo Motor Car
Company was used in this investigation. The block was
one-half (f) inch thick, two (2) inches long and one and
oneéhalf (1%) inches wide. The block was smooth to within
one-thousandth.(0.001) of an inch, which was not flat enough
for this work. The side which was not to be plated was
made as smooth as possible, using 240 grinding compound on
a metallographic polishing wheel. The side to be measured
was polished in the same manner. In addition it was made
optically flat by hand polishing. The material used for
polishing was levigated alundinum. The block was plated
with thirty (30) minutes of nickel and polished very
accurately again. Then plated with three (5) minutes of
chromium.

In order to measure this very thin coat of chromium
it was necessary to have an instrument which was capable of
measuring very small variations in thickness. The Chamber-
lain Recording Interferometer was the only instrument known
and available which would meet the requirements of this
problem. It was capable. by the setting of the masks in the
field of view. to the helium red and blue lines. of measure-

ments to four millionths (0.000004) of an inch. For an

-11-

illustration of this instrwment refer to Plate 2 of this
thesis.

The cOpper and nickel plates were obtained from
plating baths made up, in liter beakers. The eight centi-
meter'measurements were carried out using a plating bath of
chromium. made up in a liter beaker and heated over an
electric hot plate. However the fourteen and twenty-eight
centimeter measurements were carried out in a chromium bath
of the same composition, only made up in the glass aquaria
as shown in Plate 1. This apparatus was built in the fol-
lowing manner:

A glass aquaria 18' x 11' x 6'. ( the six;inch di-
mension being the width), was fitted with three plates of
glass cut from.p1ate glass found around the laboratory.

Two of these glass plates (16} x:9) inches were used as
sides, and the other (16% lefi) inches was used to form
a bottom to the box. The above was done to make a glass
box conforming more closely to the block.-and not let any
eddy current get around the edge of the block.

A lead anode was cut to fit into the end of the box
formed by these plates. and was fixed solidly at this
point by bending over the end of the aquaria. The block to
be plated was wound with one turn of copper wire. This was

soldered securely to the block at all points. The block

was suspended from a movable cathode rod. also of capper,
which could be moved along the top of the glass box formed
by the glass plates mentioned on the preceding page.

A.coil of pyrex glass was used to pass steam into
the chromium plating bath to heat it to the desired temp-
erature. (between forty and fifty degrees centigrade).

The lower temperature being the most satisfactory. The coil
was made from.five feet of pyrex tubing. The time required
to heat the bath from twenty degrees to forty-six.degrees
centigrade. was about three quarters of an hour.

The capacity of the aquaria. when filled to within

about two inches of the top, was about twelve liters.

-13-
E.X P E R I MiE N TQA L P R O C E D U'R E

A.block of steel two (2) inches by one and one—half
(1%) inches by one-half (f) inches was used for most of the
experiments. The steps of preparing it for plating and
measuring were as follows:

The block of steel was ground flat on the side of a
fine emery wheel. Then.the piece was polished on a regular
*metallographic polishing table. using three different
grinding compounds, namely; 240. 360 and levigated alundin-
mm. This polishing operation was performed with a great
deal of care, to keep the surface flat. or course with
such a large surface to be worked down, the time required
to complete the polishing operation was very long.

After obtaining this smooth and flat surface, the
block was plated. as will.be described a little farther on.
A.pad of pitch was used in the first few attempts of polish-
ing these plates. The pad was made by taking a pitch of a
consistency slightly less rigid than sealing wax and melt-
ing it in a sand bath dish. Upon cooling. the pitch was
cut into squares having about a centimeter to the edge.

The cuts were made deep enough so as to form little pads of
pitch which would give slightly upon the block passing over
them. This pitch pad made an excellent buffing material.

but it required nearly twenty-four hours of polishing move—

ments over the surface in order to give even a fair polish
to the plated surface of the block.

Finally a piece of plate glass. flat to within five
ten-thousandths (0.0005) of an inch was substituted for the
pitch pad.and levigated alundinum was used as the abrasive
material. The possibilities are that the work was not as
well finished as in the case of the pitch pad, but the
time that was saved was very great. The results which were
obtained from.plates prepared in this manner were entirely
satisfactory.

It must be noted here that in all of the polishing
operations, the only force acting down upon the piece was
the attraction of gravity for the block of steel.

The block was now ready for the first plate. In
the early runs the block was cleaned well in a sodium
hydroxide (100 grams per liter) electrolytic cleaning bath;
washed well in running water, and then immersed in the
copper cyanide plating bath where it remained for two mine
utes, at two amperes per square decimeter and forty-five
degrees centigrade. However in the later experiments with
this same block, nickel was plated directly on the steel.
The cyanide cOpper was buffed. the plate cleaned once more
and about twenty to thirty minutes of acid cOpper, at one

ampere per square decimeter and twenty-one degrees centi-

-15-

grade, was put on. The acid capper was buffed to a very
highly polished surface, much more easily than the original
stee1.block. After the acid c0pper plate was all buffed
and optically flat, the surface was again cleaned electro-
lytically and the block immersed in a nickel plating bath.
The nickel was plated from.a bath running at one-half an
ampere per square decimeter and at a temperature of about
thirty-five degrees centigrade. Several different nickel
baths were used for plating. They were all used at the
same current density and temperatures as mentioned above.
with fairly consistent results. After the nickel bath was
used for some time. trouble was had with pitting. A cubic
centimeter or two of hydrogen peroxide was added to each
liter of nickel bath, to take care of the excessive gassing
at the cathode.

For the composition of the various plating baths
used in this work refer to pages 43 to 45 inclusive.

After plating several times with copper and nickel.
alternately, the block was ready to have the final
chromium plated upon it for measuring. Before the block
was placed in any plating bath, a trial was made with.a’-
other piece of steel. nickel plated, of the same size and
shape to be sure that the plating bath was in the best of
working order. Previous to these trials, however. many

runs were made to determine the best conditions and the

-16-

best compositions of plating baths for the various plating
operations. It was very essential that all of the factors
influencing the plating of chromium be carefully recorded
at the time of each plating attempt. from a study of
chromium.plating the following factors were listed as in-
fluencing the plating of chromium; composition of the bath.
this factor was more or less constant. as the same bath was
used for all trials; the current density used; the distance
from.the anode to the cathode; length of time of plating
and the temperature of the bath. From.this data the con-
clusion could be drawn as to Just what the relative order
of importahce of these factors would be.

After the block was plated with chromium.it was
placed in a bath of clean, running water for several min-
utes and then the block was dried with a towel. The spec-
imen was then placed in a dessicator and remained there for
at least a half hour or perhaps over night.

As mentioned under-the introduction, the instrument
used to make these accurate measurements was the “Chamber-
lain Recording Interferometer“. An illustration of this
instrument is found on Plate 2. The platform was cleaned
free of dust particles. as well as the block and tip of the
plunger. The dust was removed with a camel's hair brush.
After this removing of dust particles. the block was placed

with a twisting motion and using considerable force. upon

the platform. Then the interferometer was slipped down the
supporting post until the tip of the plunger just touched
the surface of the block. This could be observed by the re-
flection in the highly polished surface of the block.

When the instrument was in this position and a
source pf white light was placed in front of the colimat-
ing lens, (the telescopic looking projection at the lower
right hand end). a spectra characteristic of white light
could be seen by looking through the eye-piece of the tele-
scope at the upper left hand corner of the instrument. At
the same time streaks could be noticed running vertically in
the field of view. These streaks were caused by dust
particles in the slit of the colimating telescope. so we
will call them dust lines. The dust lines make possible a
very good means of adjusting the interferometer. When the
interferometer was in proper adjustment, these dust lines
were straight, but when it was out of adjustment, the lines
were bent. If the lines were bent, the upper adjusting .
screw was turned until the lines were straight, which took
only a very slight movement of the adjusting screw, some-
times just touching it would change the lines from bent to
straight. At this point the interference bands appeared
very faintly in the field of view. By turning the other
adjusting screw with the same degree of care it was possible

to bring the bands out into sharp contrast with the light

back ground.

Upon obtaining these sharp dark bands, the inter-
ferometer was prepared for the next adjustment.

The next adjustment consisted in setting the two
masks so as to make the instrument read in even decimals of
an inch. With these masks set in this manner the appear-
ance of each new band signified a certain even decimal of an
inch change. This also applied if a band vanished from the
field of’view. For these measurements, the masks were set
on the red and blue lines of helium. This was accomplished
in the following manner; the helium tube was placed in front
of the slit of the collimator. The current for the helium
tube was furnished by a transformer connected on one side
to the lighting circuit, of one hundred and ten volts. and
the other side connecting with a Ford spark coil. Looking
into the eye-piece, the spectra of helium was observed, a
red line at the top and two blue lines at the bottom.were
the only lines that were of interest for this adjustment.
The upper mask was slipped down until it,just began to e-
clipse the red line. Then the lower mask was slipped up
until it just began to eclipse the upper blue line or the
brightest blue line. The instrument was then in adjust-
ment for reading to even decimals of an inch.

The source of white light was placed again in front
of the collimator. Then the plated block was placed under

- 19 -

the plunger. The block was placed on the platform in the
manner that has been described. so as to make the air film
below it as nearly uniform as possible and also to make the
block firm, so that constant measurements of the same point
could be made. The plunger was let down with a force of
sufficient amount. so that a distinct click could be heard.
This same force was duplicated in each case that the plunger
was let down. Four readings of the number of bands present
in the field of view were taken and averaged. Fractions of
bands were read to within one tenth of a band.

After the readings were taken at a point on the
plate, with the chromium.plate still on, the plunger was
lifted out of the way by the means of a thin glass plate
and the plate was left there to protect the plunger from
any acid fumes or spray. Then a thin glass rod. with a
small swab of cotton soaked in hydrochloric acid twisted
onto it, was inserted between the glass plate and the block
thus removing the chromium plate at that point. The block
was washed well with water, using a cotton swab and seeing
that the block was not disturbed the least bit. Finally
the water was dried off with a piece of cotton. Then wait-
ing for at least fifteen minutes, to be sure that the
temperature of the block was back to that of the room tem»
perature, the plunger was let down at the exact spot where

it had rested before the plate had been removed. The plate

- 20 -

being off, the number of bands in the field of view this
time were different. The difference between the average
reading before removing the plate and after removing the
plate gave, of course. the number of bands representing the
thickness of the chromium plate at that point. The
difference multiplied by 0.00004, (the number of inches rep-
resented by a change of one band in the field of view).

gave the thickness of the chromium.plate in inches at the
point measured. This procedure was followed for the remain-

der of the points on the block and for each trial.

1 W3
4‘ * "42A

3"
“an -
- . . ~‘

Dh'

 

 

Q

ov'-’.

 

 

 

 

Trial
1 - 60
61
62
63
64
65
66
67
68
69
70
'71
72

74
75
76
77
78
79
80
81
82

Plate Amps ./dm2
Cu-Ni

Cr-l

. .A

16
10

10

DATA
Time

30 min.

GUUUUUUUUGUUQQUGUUUGUW

Temp.

40
49°
49.5
49.5
51

49.5
49.5
49.5

49.55

41.0
49.5
49.5
49.5
49.8
50.0
50.0
50.0
51.0
51.0
51.0
51.0

Results

Good.

No good.

3311‘.

Good.

Poor.

No good.

Trial
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101

Plate Amps./dm2

Cr-l

8
8
1
.5
16
10

-22..

DATA 2

Ol 03 03 (A 01 01 0! M 03 01 0‘ 0| 0' 0' 0'
I

Temp 0

45.9
48.0
21.0
41.0
46.0
47.0
45.5
46.0
46.0
46.0
46.0
46.0
46.0
47.0
46.6
46.0
47.5
48.8
48.6

Results
Good

I

s

s

w
HO”good
w w
w w
w w
w w
w s
s w
w w
s s
Fair

I

w
Good

Plating Trial 61.

Before removing plate.

Trial 1
Point

1 43
2 36
3 36
4 59
5 49
6 -I6
7 -7
8 ll
9 53

After removing plate.

Trial 1

Point

38
29
33

46
-23
-10

IOQQOOUIUFOINH

43

2

- 23 -

DATA 3

3

4

Number of bands in view.

2

41
37
36
58
47
-16
-7
10
53

3

4

41
38
36
57
48
-16

11
53

Mean

41
37
36
58

48 «

~16
-7
12
53

Before

Mean

Number of bands in view.

38

31

33

44

~23

-10

45

37
3O
33

45
-23
-12

6

44

38
3O
33

45
-23
-IO

7

44

38
30
33

Due to slip no data here.

45
-23
-10

44

41
37
36

48
-16
—7

11

53

Measurement No.

8 cme

Mean.

41
37
36
58
48
-16

ll
53

Diff.

‘OOIO’QOJ

Thickness.

0.000120“

0.000280.

0.000120“

0.000120"

‘ 0.000280”

0.000120-
0.000200-
0.000360“

Measurement No. l

8 cm.

.000280'

 

.000120' c o 0 .000120'

”.000360"

.ooozoo- 0 0/0 Slip

 

 

.000120',”9 o 0 .000120'
.000280'

-25-

DATA 4 8 cm.

Plating Trial 69. Measurement No. 2.

Before removing plate
Trial 1 2 3 4 mean.
Point number of bands in view.
1 70 71 70 70 70
2 -22 -22.5 -22.3 -22.3 _ -22.3
3 -10.3 -10.3 -10.2 .10.4 ~10.3
4 -15.3 .15.6 .15.4 -15.4 .15.4
5 -12.4 -l2.4 -l2.5 ~12.4 -12.4
6 39.2 39.3 39.1 39.2 39.2
7 -l5.l ~15.l -15.2 ~15.l -15.1
8 6.9 7.0 7.1 7.0 7.0
9 -38.5 -38.4 -38.5 -38.5 -38.5

After removing plate
Before

Trial 1 2 3' 4 Mean ZHean Diff. Thickness
Point Number of bands in view.
1 69 69 69 69 69 70 1 0.000040"
2 -26.8 -26.7 -26.8 -26.8 -26.8 -22.3 4.5 0.000180"
3 -12.8 ~12.7 -12.9 -12.8 -l2.8 -10.3 2.5 0.000100"
4 -l7.8 -17.8 ~17.7 -l7.8 -l7.8 -l5.4 2.4 0.000096“
5 -15.4 -l5.4 -15.4 -15.5 ~15.5 ~12.4 3.1 0.000124“
6 37.5 37.5 37.5 37.4 37.5 39.2 1.7 0.000068"
7 -17.3 -l7.3 ~17.3 -l7.2 -17.3 -15.1 2.2 0.000088“
8 3.6 3.6 3.6 3.5 3.6 7.0 3.4 0.000136“
9 —40.0 -40.l -40.l -40.l ~40.l o38.5 1.6 0.000064"

measurement No. 2

.000180'

 

.000040' 0 o 0 ‘.000100'

2.000064”

.000136' c 0/ .000096"

.000088' 0 o 0 .000124“

 

 

 

.000068‘

Plating Trial 70.

Trial
Point

$7 CD '4 0t (3 lb 0' 00 i4

- 27 -

DATA 5

Before removing plate
I 2 3 4
Number of bands in view.

32.0 32.2 32.1 32.1

-24.4 —24.5 -24.3 -24.4

21.4 21.3 21.3 21.2

15.9 16.0

14.9

16.0
14.9

16.1

14.9 14.8

-31.3 -31.3 -31.2 -31.3

31.5 31.5 31.6 31.5

36.3 36.4 36.3 36.2

6.5 6.5 6.5 6.5
After removing plate
Before
1 2 3 4

lhan» Mean
Number of bands in view.
27.? 27.7

27.6 27.7 32.1

-28.3 -28.4 -28.3 .28.3 ~24.4

18.3 21.3
16.0
14.9

-31.3

18.3
12.5

18.2 18.3

12.4 12.5 12.5
10.3 10.1

~35.4 -35.3

10.2
-35.3

10.2
—35.3
31.5

27.8 27.8

32.7

27.8
32.8

27.8

32.6 32.7 36.3

9.3 9.3 9.2 9.3 6.5

Measurement No.

Mean

8 cm.

3.

32.1

~24.4
21.3
16.0
14.9
-31.3
31.5
36.3
6.5

Diff.

4.4
3.9
3.0
3.5
4.7
4.0
3.7
3.5
2.8

Th1 cm... 0

0.000176“
0.000156“
0.000120“
0.000140“
0.000188“
0.000160“
0.000148“
0.000144“
0.000112“

 

Measurement No. 3
8 cm.
.000156'
.000176“ 0 0 .000120'
”.000112'
.000144' o/o .000140"
.000148' c 0 .000188“

 

 

 

.000160“

DATA 6 8 cm 0
Plating Trial 78 iHeasurement No. 4.
Before removing plate

Trial 1 2 3 4 . Mean
Point Number of bands in view.

1 11.5 11.4 11.5 11.5 11.5
2 No plate at this point.

3 13.9 14.0 14.1 14.0 14.0
4 9.0 9.1 9.0 9.0 9.0

5 5.3 5.2 5.3 5.4 5.3

6 10.2 10.3 10.2 10.2 10.2
7 3.8 3.9 3.7 3.8 3.8

8 6.7 6.7 6.6 6.7 6.7

9 8.0 8.0 8.1 8.0 8.0

After removing plate
Before
Trial 1 2 3 4 ‘Mean IMean Diff. Thickness

Point Number of bands in view.

I 9.5 9.7 9.6 9.6 9.6 11.5 1.9 0.000076“
2 no plate at this point

3 10.6 10.6 10.6 10.5 10.6 14.0 3.4 0.000136“
4 5.3 5.4 5.3 5.3 5.3 9.0 3.7 0.000148“
5 3.2 3.1 3.2 3.2 3.2 5.3 2.1 0.000084“
6 7.0 7.0 6.9 7.0 7.0 10.2 3.2 0.000128“
7 1.6 1.5 1.6 1.6 1.6 3.8 2.2 0.000088“
8 6.7 6.6 6.7 6.6 6.7 6.7 0.0 0.000000“
9 7.2 7.2 7.2 7.2 7.2 8.0 0.8 0.000032“

-30..

Measurement No. 4

 

8 mm.
.ooooooIt
.000076“ c o 0 .000136“
”.oooo3sw
.000000' c 0”///5/ .000148“
.000083" c o 0 .000084”

 

 

 

.000128"

- 31 -

DATA 7 14 cm.
Plating Trial 79 measurement No. 5

Before removing plate

Trial 1 2' 3 4 Mean
Point Number of bands in view.

1 6.4 6.5 6.5 6.6 6.5
2 ~17.5 ~17.5 -l7.5 -17.5 -17.5
3 5.6 5.4 5.4 5.4 5.4
4 5.0 5.0 5.0 5.0 5.0
5 8.0 7.8 7.9 8.0 7.9
6 12.1 12.1 12.2 12.0 12.1
7 Blisters.

8 Blisters.

9 Blisters.

After removing plate
Before

Trial 1 2 3 4 Mean Mean Diff. Thickness

Point Number of bands in view.

1 4.0 4.2 4.2 4.3 4.2 6.5 2.3 0.000092“
2 -19.7 -19.8 -19.7 -19.7 -19.7 -17.5 2.2 0.000088“
3 This not obtained due to slip of interferometer.

4 This not obtained due to slip of interferometer.

5 5.4 5.5 5.5 5.5 5.5 7.9 2.4 0.000096“
6 9.9 9.8 9.8 9.8 9.8 12.1 2.3 0.000092“
7 Blisters.

8 Blisters.

9 Blisters.

-32 ..

Measurement No. 5-

14 cm.

.000088“

 

.000092" c - o o Slip

/. Blisters

Blisters o o A Slip

Blisters o o o .000096“

 

 

 

.000092“

-33-

DATA 8 14 One
Plating Trial 83 Measurement N0. 6

Before removing plate

Trial 1 2 3 4 Mean.
Point‘ Number of bands in view.

1 13.8 14.0 13.9 14.0 13.9

2 10.0 I 9.8 9.7 9.9 9.85
3 7.5 7.2 7.4 7.0 7.3

4 7.8 7.9 8.0 7.9 7.9

5 4.0 3.9 4.1 4.0 4.0

6 7.0 6.9 6.8 6.8 6.9

7 7.0 7.0 7.0 7.0 7.0

8 7.0 6.9 7.1 7.0 7.0

9 6.9 7.1 7.1 7.0 7.0

After removing plate
Before

Trial 1 2 3 4 mean JMean Diff. Thickness

Point Number of bands in view.

1 6.5 7.5 7.0 7.0 7.0 13.9 6.9 0.000276“
2 8.0 8.0 8.0 7.9 8.0 9.85 1.85 0.000074“
3 5.2 5.0 5.2 5.1 5.1 7.3 2.2 0.000088“
4 6.3 6.2 6.4 6.3 6.3 7.9 1.6 0.000064“
5 1.9 2.0 2.0 2.1 2.0 4.0 2.0 0.000080“
6 4.0 4.1 3.9 4.0 4.0 6.9 2.9 0.000116“
7 5.0 5.0 5.0 5.0 5.0 7.0 2.0 0.000080“
8 4.3 4.6 4.5 4.8 4.5 7.0 2.5 0.000100“
9 6.2 6.1 6.3 6.2 6.2 7.0 0.8 0.000032“

.. Measurement No. 6

14 cm.

.000074'
.000276 “ o o 0 .000088“

 

”.000032“

.000100- c e/o .000034-

.000030' 0 O 0 .000080“
.000116'

 

 

 

DATA.9 14cm.

Plating Trial 84 Measurement No. 7

Before removing plate
Trial 1 2 3 4 Mean
Point Number of bands in view.
1 11.5 11.6 11.2 11.2 11.4
2 10.0 10.0 10.2 10.1 10.1
3 6.6’ 6.5 '6.5 6.5 6.5
4 8.0 8.0 8.0 8.0 8.0
5 7.2 7.1 7.0 7.0 7.1
6 8.0 8.0 8.0 8.1 8.0
7 8.9 9.0 8.8 8.9 8.9
8 8.0 8.3 8.5 8.3 8.3
9 8.5 9.0 9.0 8.5 8.8

After removing plate
Before

Trial 1 2 3 4. Mean Mean Diff. Thickness

Point Number of‘bands in view.
10.2 10.5 10.4 10.2 10.3 11.4
9.0 9.1 9.0 8.9 9.0 10.1
4.5 4.4 4.6 4.5 4.5 6.5
7.0 6.9 6.7 7.0 6.9 8.0

QQQQOIIFMNH

6.9 6.9 6.9 6.9 6.9 8.0
6.2 6.3 6.2 6.5 6.3 8.9
7.1 7.3 7.3 7.0 7.2 8.3
6.2 6.3 6.5 6.4 6.3 8.8

1.1 0.000044“

1.1 0.000044“

2.0

0.000080“

1.1 0.000044“

1.1
2.6

Poor nickel at this point, no measurement.

0.000044“
0.000104“

1.1 0.000044“

2.5

0.000100“

- 35 -

Measurement No. 7

14 cm.

.000044'

 

.000044“ 0 o 0 .000080“

’a.000100“i

.000044' c o/o .000044"

.000104“ 0 o o Poor Nickel

 

 

 

.000044“

Plating Trial 8?

Trial

Point

tom-COOMIFMNH

1

-37-

DATA 10

14 cm.

Measurement No. 8

Before removing plate

2

3

Number of bands in view.

6.0
8.9
5.6
5.8
7.0
7.9
8.0
9.8
6.2

Trial 1

Point

‘OQQODQIFUNH

5.9
6.0
4.0
3.0
4.0
7.0
8.0
8.5.
6.0

6.1
9.0
6.0
6.0
7.0
8.0
8.0
10.0
6.3

5&9
9.0
6.0
6.0
6.9
8.0
8.0
9.8
6.2

After removing plate

2

3

’4

6.0
8.9
5.8
6.0
7.0
8.0
8.0
10.0
6.1

Before

Mean

6.0
9.0
5.9
6.0
7.0
8.0
8.0
9.9
6.2

Mean Diff. Thickness

Number of bands in view.

6.1
6.0
4.0
3.0
4.0
7.0
8.0
8.5
6.0

6.1
6.0
4.1
3.1
4.0
7.0
8.0
8.9
6.1

5.8
6.0
4.0
3.0
4.0
7.1
8.0
8.5
6.2

5.9
6.0
4.0
3.0
4.0
7.0
8.0
8.6
6.1

6.0
9.0
5.9
6.0
7.0
8.0
8.0
9.9
6.2

0.1 0.000004“
3.0 0.000120“
1.9 0.000076“
3.0 0.000120“
3.0 0.000120“
1.0 0.000040“

0.0 0.000000“

1.3 0.000052“
0.1 0.000004“

Measurement No. 8

l4 Clue

.000120“

 

.000004“ c o 0 .000076“

. .000004~
.000052- o 0/0 .000120-

 

 

.000000“ 0 o 0 .000120“

 

.000040“

Plating Trial 100

Trial
Point

OmdmmhMNl-J

Trial
Point

'OODQOOOInbuNH

DATA 11

Before removing plate

28 cm.

Measurement No. 9

1 2 3 4 Mean
Number of bands in view
6.0 6.2 6.1 6.0 6.1
8.9 9.0 9.0 9.1 9.0
10.0 10.0 10.0 10.0 10.0
6.3 6.2 6.3 6.3 6.3
6.0 6.0 6.0 6.0 6.0
9.0 9.0 ' 9.0 9.0 9.0
8.0 8.0 8.0 8.0 8.0
3.0 6.0 6.0 6.0 6.0
5.1 5.2 5.0 5.2 5.2
After removing plate
Before
1 2 3 4 Mean Mean. Diff. Thickness
Number of bands in view.
3.5 3.6 3.5 3.5 3.5 6.1 2.6 0.000104“
8.2 8.0 8.0 8.1 8.1 9.0 0.9 0.000036“
9.1 9.2 ' 9.0 9.1 9.1 10.0 0.9 0.000036“
5.5 5.3 5.4 5.4 5.4 6.3 0.9 0.000036“
4.5 4.3 4.5 4.5 4.5 6.0 1.5 0.000060“
Specimen was moved at this point. no reading.
7.1 7.1 7.1 7.1 7.1 8.0 0.9 0.000036“
5.1' 5.1 5.2 5.0 5.1 6.0 0.9 0.000036“
4.9 5.1 5.0 5.0 5.0 5.2 0.2 0.000008“

- 4o -
measurement No. 9

28 cm.

.000036'

 

.000104“ 0 'f o 0 .000036“-

a.oooooa-
.000035- To o/o .ooooae-

 

 

.000036' 0 0 0 .000060'

 

Slip

-41-

DAIA 12 28 em.
Plating Trial 101 measurement No. 10

Before removing plate

Trial 1 2 3 4 Mean
Point Number of'banda in view

1 7.0 7.2 7.1 7.1 7.1
2 7.9 8.0 8.0 7.9 8.0
3 8.5 8.6 8.3 8.5 6.5
4 6.0 5.9 5.9 6.1 6.0
5 12.0 12.0 12.0 12.0 12.0
6 5.9 5.8 6.0. 6.0 5.9
7 6.2 6.3 6.1 6.1 6.2
8 13.5 13.1 13.2 13.3 13.3
9 8.0 7.9 8.1 8.0 8.0

After removing plate
' Before
Trial 1 2 3 4 Mean Mean Diff.Thiekneea

5.3 5.2 5.3 5.3 5.3 7.1 1.3 0.000072-
6.1 6.2 6.2 6.1 6.2 8.0 1.8 0.000072-
6.5 6.6 5.4 6.5 5.5 3.5 2.0 0.000080“
4.0 4.1 4.0 3.9 4.0 6.0 2.0 0.000080“
10.0 10.1 10.0 10.0 10.0 12.0 2.0 0.000080“
4.0 4.0 4.0 3.9 4.0 5.9 1.9 0.000076“
4.8 5.0 5.0 4.9 4.9 6.2 1.3 0.000052-
12.0 11.9 12.0 12.0 12.0 13.3 1.3 0.000052-

‘OQQOOOUIDOINH

5.0 5.0 5.0 5.0' 5.0 8.0 3.0 0.000120"

-42-

Measurement No. 10

.000072'

.000052'

.000052'

28 cm.

.000072'

 

 

O O

,»

b

 

 

.000076'

.000080‘

.000120"
.000080'

.000080'

-43..

DATA 13
SulphateTest Using Kocour Sulphate Test Set.
Trial Ppt. Tube 1 Ppt. Tube 2 Difference Grams per Liter

1 5.5 O 5.5 4.125
2 5.2 0 5.2 3.900
5 5.5 0 5.3 3.975
4 5.6 0 5.6 4.200
5 5.7 0 5.? 4.275

Mean - 4.095

Reading on Baume Scale.

30° at 21° 0.

Composition of Chromium Bath.
Chromic Acid 240 grams per liter
Sulphuric Acid 1.2 grams per liter

Composition of AcidCopper Bath.
Capper Sulphate 200 grams per liter
Sulphuric Acid 50 grams per liter

-44-

COMPOSITION OF NICKEL BATHS.

NICKEL NO. 1
Boric Acid ‘ 15.46 g/L.
Nickel Sulphate 140. g/L.
Ammonium Chloride 13. g/L.

NICKEL NO. 2
Boric Acid 15.46 g/L.
Nickel Sulphate 70. g/L.
Ammonium Chloride 13. g/I...

NICKEL F0. 3
Boric Acid 15.46 g/L.
Nickel Sulphate 270. g/‘L.
Amhanium Chloride 13. g/L.

NICKEL HO. 4
Boric Acid 15.46 g/L.
Nickel Sulphate 14o. g/L.
Sodium Chloride 15. g/L.

NICKEL NO. 5
Boric Acid 15.46 g/L.
Nickel Sulphate 100. g/L.
Nickel Chloride 30. g/L.

-44-

COMPOSITION OF NICKEL BATHS.

NICKEL NO. I
Boric Acid . 15.46 g/‘L.
Nickel Sulphate 140. g/L.
Ammonium Chloride 13. g/L.

NICKEL NO. 2
Boric Acid 15.46 g/L.
Nickel Sulphate 70. g/L.
Ammonium Chloride 13. g/L.

NICKEL NO. 3
Boric Acid 15.46 g/L.
Nickel Sulphate 2'10. g/L.

Amonium Chloride 13. g/L.

NICKEL N0. 4
B‘oric Acid 15.46 g/L.
Nickel Sulphate 140. g/L.
Sodium Chloride 15. g/L.

NICKEL NO. 5
Boric Acid 15.46 g/L.
Nickel Sulphate 100. g/L.
Nickel Chloride 30. g/L.

NICKEL N0. 6
Boric Acid 15.46 g/L.
Nickel Sulphate 140. g/L.
Magnesium.0hloride 25. g/L.

NIGICEL NO. 7
Boric Acid 15.46 g/L.
Nickel Sulphate 140 g/L.
Ammonium Sulphate 1'7. g/L.

NICKEL NO. 8

Boric Acid 15.46 g/L.

Nickel Sulphate 140. g/L.

Sodium.Fluoride 11. g/L.
NICKEL NO. 9

Boric Acid 15.46 g/L.

Nickel Chloride 119. g/L.

NICKEL N0 . 10
Boric Acid 15.46 g/L.
Nickel Chloride 119. g/L.
Ammonium Ghloride 13. g/L.

-46-
G O N G L U S I O N'S

After working with the apparatus and using the '
same point on the block. it was found unnecessary to have
the surface of the block Optically flat. In the measure-
ments recorded in the data, the block was placed on the
platform and not moved during the time that a certain point
was being measured. Therefore any irregularities in the
block would not affect the measurements as long as the block
was smooth enough to rest firmly upon.the platform.

The later data shows the number of bands in the
field of view as being considerably less than in the early
measurements. The reason for this is two-fold:- First. the
fewer the number of bands the more rapidly the readings can
be made. Second, the fewer and the wider the bands the
more accurately they record the thickness of the chromium
plate. That is because even a fraction of a band change in
the larger and broader bands can be readily observed.

By a series of emperiments it was found that with
the wiping off of the block with water after the acid had
reacted, the block was cooled sufficiently to allow it to
come back to the room temperature in a period of less than
five minutes. In these trials the length of time takeawas
fifteen minutes, so as to be absolutely certain that no

error due to the expansion of the block. by the heat of re-

-47-

action, would be present.

From a study of the graphic representation of the
data, the following conclusions can be drawn:

(1) The thickness of the plate varies directly with
the current density used.

(2) The higher the temperature of the bath, the
higher the current density must be ih order to give the same
thickness to the plate.

(3) The metal distribution over the block is better
at the greater distances from the anode.

(4) The throwing power is very poor. For at the
greater distances the plate becomes thin as compared with
the plates received closer to the anode.

(5) One cause for the extremely poor throwing power
of this bath is the high.sulphate content, which has been
verified by other workers in the field.

(6) The difference in thickness of the plates at
various distances from.the anode. was used to determine the
throwing power.

(7) The throwing power of this bath measured by the
thickness of plates is -31.4% .

(1)

(2}

(3')

('4)

(5)

-49-

B’I B L I 0 G R.A.P H I E S .

Throwing Power.
The Throwing Power of Plating Baths-Arndt and Clemens.
Chemo Ztg. _4_§.. 925 (1922).

A Study of the Throwing Power and Current Efficiency
of Zinc Plating Solutions - Horsch and Fuwa.
Trans. Am. Electrochem. Soc. _4_1_. 363 (1922).

Current Distribution and Throwing Power in Electro-
deposition --- Blum, I. and Haring, H. 3.
Trans. Am. Electrochem. Soc. .44, 313 (1923).

Throwing Power, Cathode Potentials and Efficiences
in Nickel Deposition - Haring. H E.
Trans. Am. Electrochem. Soc. 56;. 10? (1924).

Cavity Scale for Measuring Throwing Power-Pan. L. C.
Metal Industry. 28. 271 (1930).

(6)

('7)

(8)

(1)

(2)

-50-

The Effect of Various Metallic Sulphates upon the
Throwing Power of a Chromium Plating Bath - Stout and
afirole

Industrial Eng. Chem. 22 . 1324 (1930).

The Throwing Power of Chromium Baths ~Farber and Blum.
Bur. Standards 3'. Research 4. 27 (1930).

Throwing Power of Plating Solutions with Particular
Reference to Certain Zinc Plating Solutions - Braund.

Trans. Faraday Society. 31. 661 (1931).

Measurements .

The Radius of Molecular Attraction-Chamberlain, C. W.
Physics Review A a, 170 (1910).

Gauges and Pine Measurements -- Bolt, 1‘. H.
McMillan 8: Co. London 2 Volumes (1929).

 

 

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