HEGH FREQUE CY T§?M?EGN OF SGL‘éE
MGNGBASSC A59?) WEASSC A5233 3%
NOR-AQUEWS MEDRA

Thai: for fho Dogma of M. S.
MICHIGAN STATE UNWERSRTY

Lawrenco La Roy Fleck
1958

 

LIBRARY

Michigan State
University

 

 

HIGH FREQUERCY TITRATION OP SOL‘EE MCI-EOBASIC
AND DIBASIC ACIDS IN ROE-AQUEOUS KLEIA

BY

Len-once Laney Fleck

Submitted to the College of Science and Arts of Michigan
State University of Agriculture and Applied Science
in partial fulfillment of the requirements
for the degree of

RA STISR OF SC I MTCE

'Department of Chemistry

1958

AC KN OJJIEEG-MEZNTS

The euthor ie deeply indebted to
Dr. Andree Timnick for hie guidance and
hie help given throughout the entire

inveetigetion and preparation of thie
mCII. e

Acknoeledgment ie eleo extended to .
Er. Dente A. Conetenzo for hie helpful
euggeetione in the oonetruction or the
high frequency titration epparetue.

fl iii-#19112 iii-{8341'

ii

VITA

Heme: Lawrence LeRoy Fleck
Born: February 24, 1931 in Kalemezoo. fiichigan

St. Augustine High School, Kalemezoo,

Acedemic Cereer:
iicbigan (1945—1949)

Western Kichigen College, Kelemeeoo,
Kichig en (19 51-19 55)

fiichigen State University, East Leneing,
Elohigen (1955- )

Degreee Held: AB. 3. Western Eichigan College (1955)

111

HIGH FREQUENCY TITRATION OF SOME MONOBASIC
AND DIBASIC ACIDS IN NON-AQUEOUS MEDIA

3!

Lawrence LeRoy Fleck

AN ABSTRACT

Submitted to the College of Science end Arts of Hichigen
State University of Agriculture and Applied Science
in partial fulfillment of the requirements
for the degree of

MASTER OF SC IENCE

Department of Chemistry

Year 1958

Approved W

 

A {13 '33 AC '1’

A eteble high frequency titration epperntue wee
eonetructed. Thie instrument, utilising e plete type
cepecitence cell, was employed for all high frequency
titretione conducted in this investigation.

ihe high frequency titration resulte obtained in
thin investigation eere evaluated by comparing these
reeulte with those obtained by conductimetric end
potentiometric methods. The ehepe of the high frequency
and conductimetric titration curvee eere eimiler for’ell
eoide titrated.

Tetrobutylommoniun hgdroxide wee tested on e titrant
for the high frequency titration of come monobaeic and
dibeeic acids diesolved in non-aqueous colvente. The
beet over-e11 titration rcaulte were obtcincd for acid:
dieeolved in 60% benzene-20S methanol. chcr solvents
examined were dimcthyl forwamide, methyl isobutyl ketone,
Bofi'bennene-lofi methanol. and so; benzene-fioj'methanol.

The high frequency titration: of benzoic and
eelioylic ecid dieeolved inmemhyl isobutyl ketone were
uneuoceeeful due to poorly defined titration and points.
Phenol, however. eee eucaeeefully titrated in methyl
ieobutyl ketone eith tetrebutylemmonium hydroxide.

The following monobeeic end polybeeic ecide dieeolved
in 80% benzene-20% methanol were successfully titrated

V

with tetrabutylemmonium hydroxide: adipic, bencoic,
citric. fumaric, maleic, malonic, oxalic, salicylic,
eebacic, and auccinic acids and vanillin. Tuo end
points in the titration curves, corresponding to the
neutralization of both carboxyl groups, were obtained
for the dibaeic ecide. The second titration end point
for these acids was sharper than the first. Citric
acid, a tricarboxylic acid, gave two good and pointe.
The third end point for citric acid was poorly defined.

The titration of fumaric and maleic acid mixturea
dieaolved in 80% benzene-20% methanol with tetrahutyl-
ammonium hydroxide resulted in four distinct and points.
The mean percentage purity value for the total acid

content was found to be 96.3 i 2.5% for four trials.

vi

TABLE OF COETENTS

INfiiODUCTICNOOOOO0.0.00....0..ODOOOOOOOOOOOOOOOOOOOO
’iISTORICAL BACKGROUHDOOOOOOOIOOCOIOOOOOOO0.0...0....

Ron‘.qu00u. Q‘itPIMCtYYeeeeeeeeeeeeeeeeeeeeeeeeege
Eon-aqueoue High Frequency Titrimetry............

EXPERIMERTALDeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

R..g.nt.eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee
APP‘PIWIeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee
Titration PPOOOdur03eeeeeeeeeeeeeeeeeeeeeeeeeeeee
Fotentiometric Titretione........"nun...“
Conductimctrio Titrationl...u.Human"...
High FPOQUODOy Titration.......o"no...o..."

r‘ISCE'SSION OF RESULTSOOCO0.0IOOOOOOCCOOOOOOOOOOOOOOO

Inetrument Response Curvee.......................
High Frequency and Conductimetric Titretione.....
nonobaaic Acids in Retnyl Isobutyl Ketone.....
fionODOSIO ACidfl 1n Benzene-335613113110]...o........
Polybasic Acids in Benzene-Methanol...........
Potentiomotrio Titratimfloeeeeeeeeeeeeeeeeeeeeeee
Comparison of Titration Results..................
Titration of 301‘! fugixcurefleeeeeeeeeeeeeeeeeeeeee.

SUB-1*:ARY AED COEJCLITSI‘QLIOCIOOO.OOOOOOOOOOOOOOOOOOOOOOO

LITLRATLRE CITEDeoeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee.

vii

 

LIST OF TABLES

TABLE Page
I Titration. of Monobeeic Acid. with
TCtr3bUtyI-‘mmonim Hydroud.e e e e ee e e ee e e e ee e e ee 29
II Titreticne or Polybaeic Acid: uith
Totrabutylemmonium Hydroxide. e e e e e ee 0 e e e co e e e e e 31
III High P’requency Titration Result: for Fumeric
36

and ”31.10 Aflid antmleeeeeeeeeeeeeeeeeeeeeee

viii

 

LI ST OF FIGURES

FIGURE 1’ '8'
Schematic Diagram of fiodified fligh Frequency

1.
Titration ApparItUIeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

14

2. High.Frequency end Conductimctric Response
Curvee for Tetrabutylammonium,fiydroxide.......... 19

3. High Frequency Titratione of Benzoic Acid in
Several Beneene-Eethenol Mixed Sclvcnte.......... 22

4. High Frequency Titration Curves for Salicylic
Acid end Some Dicerboxylic Acids in Benzene-

u.th‘n°10eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

24

6. High Frequency end Potentiometric Titretione cf
Citric Acid in Benzene-methanol, Tetrebutyl-

”112110211113 Hydroxide Titl'.nteeeeeeeeeeeeeeeeeeeeeee 25

6. Potentiomctric Titration of Melonic Acid in
Benzene-methanol and Adipic Acid in Hethyl
Ieobutyl Ketcne, ictrebutylemmonium Hydroxide

Tltl‘mteeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

27

7. High Frequency Titration of Fumaric Acid end
Heleic Acid mixtures in Benzene-Kethcnol,

?ctrabutyammonium Hydroxide Titrant.............. 35

ix

INTRODUCEIGE

Jensen and Parrack (34), who pioneered high
frequency titratione in the United States, greatly
enlarged the scope or high frequency titrimetry by
conducting titrations in non-aqueous media.

High frequency titrations conducted in non-aqueous
solvante offer several advantages over those conducted
in aqueous solutions. The main advantages are: 1) non-
equeoue solvents can be chosen which increase the
apparent acidity or baaicity of teak acids or bases
dissolved in them and, 2) these solvents dissolve many
organic acids or bases which are not ordinarily soluble
in water.

The choice of titrant depends on the characteristics
of the solvent, the apparent acidity or basicity of the
material being titrated, and the strength of the titrant.
These are the main factors that are considered when
choosing a suitable titrant-solvent system for non-
equeous high frequency titrinctry.

Several investigators (7,11,12,25,25,25) hflVB shown
that tetrabutylammonium hydroxide in non-aqueous solvents

is a good basic titrant for potentiomctric titration and

differentiation of strong, seek, and very soaks acids in
non-aqueous media. These workers used tetrsbutylammonium
hydroxide successfully as a titrsnt for acids dissolved
in a variety of solvents including methyl isobutyl
ketone, dimethyl formsnide, cthylsnediamine, lxl benzene-
isopropyl alcohol, benzene-methanol, acetonitrile,
pyridine and others.

Wyld, 215;. (23) foxmd that tetrabutylantnonium
hydroxide dissolved in isopropyl alcohol compared favor»
ably in performance with alcoholic potassium hydroxide
for the potentiometrie titration of phenol in several
non-aqueous solvents. In vies of this work a study eas
undertaken to test the performance of tetrabutylammonium
hydroxide as the titrant for non-aqueous high frequency

titretions or some monobasic and dibasic acids.

cihroughout this thesis acids similar in strength to
mineral acids are designated as "strong acids , those
similar in strength to unsubstituted csrboxylic acids
are designated as "weak acids", and those similar in
strength to phenol are designated as ”very seek acids”.

HISTORICAL BACKGROUND

Several reviews (18.20.54.61) of fundamental
developments in non-aqueous analysis have appeared in the
recent literature. Skolik (58) reviewed the roles of
solvents and standard solutions, the determinations of
endpoints, applications and sources of errors in non-
aquecus titrimetry. Higuchi, 3.5.31... (28) discussed the
results of spectrophotometric and potentiometric studies
mo 13 indicators in anhydrous acetic acids Van der Heine
and Dahmen (60) determined an empirical acidity potential
scale of 12 solvents by potentiometric titrations of
strong acids aith strong bases. Eilpatrick (41) dis-
cussed the theoretical and practical problems of acidity
measurements in non-aqueous media. flooser (51) included
a brief review of nonoaqueous titrations and listed a
complete bibliography of non-aqueous high frequency
titrations reported through 1954.

The {aliasing extensive revise is for the period
from 1954 through the November 10, l957 issue of Chemical

Abstractg.

Non-agneousgitrimetrz

Perchloric acid in glacial acetic acid has been used
extensively for potentiomctric titrations (4,9,15,16,17,
30,39,40,45.47) and for photometric titrations (17,28)

of a large variety of organic bacea diacolvad in glacial

acetic acid. Titration of some organic bacec using
dioxane (29,53), acetonitrilc, and nitromcthanc (9). and

chloroform (10} aa aolvonte have been performed poten-
'tiomatrically with a atendard.perchlcrio acid solution.
Blake (5) back titrated a measured exceca or perchlorio

acid in glacial acetic acid with sodium acetate for the
Tao ditterant typos

determination or come organic baaea.
of electrode ayatema (53.5?) were characterized by

neutralization titrationa with parchlcric acid.
Kolthofr (42) interpreted acid-baae titrationa in glacial

Palit and Singh (51) investigatcd phenol

acetic acid.
aa a coaolvont with glycola for organic bases tibratcd

with atandard pcrchloric acid.
Eiaukami and Eirni (50) titrated 5-acotamidoaethy1-

4-amino-9-mcthylpyrimidino in glacial acetic acid with

atandard periodic acid using a mdxcd indicator composed

of methyl violet and bromophcnol blue.
Bumerouc titrationa of acida dissolved in dimcthyl

formamide (4,14,45) benzene-methanol (3,4,4?) ethylene-
diamdne (14) or pyridina with sodium methoxide have been

performed.
Strculi (59) titrated heterocyclic amino cult: of

polymora diaaolvod in dimothyl formamide with 1,5-di-o-

tolylguanidino in 139 methanol-chloroform.
Chatton (8) titrated Eraminooalioylic acid and ita

aodium aalt with alcoholic potassium hydroxide in

methanol using acetone as the non-aqueous medium. Deal
and Wyld (12) used alcoholic potsenium.hydroxide as a
basic titrent for the titration of very weak acids using
ethylenediemine and dimethyl formamide as solvents.

Martin (48) titrated peracids, hydrogcn peroxide
and hydroperoxides as weak ecids in anhydrous ethylene-
diamine with sodium aminoethoxide using antimony
electrodes in a potentiometric titration procedure.

Kcrchmer (3?) determined mercaptane in the presence
of elemental sulfur by titration with an alcoholic
silver nitrate solution. two types of solvents were
employed in this study. One, a "regular" solvent,
contained sodium acetate trihydrate in a small amount or
water, benzene and isopropyl alcohol, and the other, an
I'aciclic" solvent contained sodium acetate trihydrste,
glacial acetic acid, methanol and bensene.

Brummet and Hollweg (6) demonstrated the applica-
bility of using chelating agents in non-aqueous titrimetry.
They determined the concentrations of several metal ions
in bensene-methsnol by adding a cheleting agent and
titrating the liberated hydrogen ions with sodium
nethoxide.

wyld,‘g§.gl, (24) compared the performance of
polarised pletinumpcelomel electrodes with glass-calomel
electrodes in titretions in which potassium hydroxide or

sodium aminoethoxide in ieopropyl alcohol was the titrent.

Henry, _e_§ 2;. (£7) titrated organic bases conduc-
tinstricslly with boron tribromide in aprotic solvents.

Several recent articles {7.11.12.19.23.25.2e)
reported the titrations of acids using tetraalkylammoniun
hydroxides as the basic titrants. dyld and Bruce (7)
found that methyl isccutyl ketone see a good differ-

entiating solvent for the titration of acids.

Non-agueous High Freguencl Titrimetr;

 

hooser (31) compared high frequency titration
results with corresponding conductimetric and poten-
tiometric titratione. He successfully titrated esak
acids dissolved in dimethyl formnmide or bensene-nethanol
sith alcoholic potassium hydroxide. Excellent results
sere reported for high frequency titrations of some very
seek acids such as‘g—hydroxydiphcnyl,phenol, pybromov
phenol, Q-nephthol and for week diccrboxylic acids such
as edipic acid. Only one endpoint was reported in the
titration of the dicsrboxylic acids.

Hell, 33,3}. (21) successfully titrated boric acid
in methanol in the presence of glycerol with sodium
hydroxide in methanol.

Iehidate and Masui (32) titrated some salts of
organic acids with perchloric acid or sodium acetate in
acetic acid.

Dean and Gain (13) titrated salicylic acid,

potassium.acid phthalete, beneoic acid, gynitrOphenol,

boric acid, ammonium bromide and ammonium iodide in
diasthyl formamide with sodium methoxide. They also
reported that gybutylamine was a suitable non-aqueous
titrant for ”stronger acids”.

Lane (43) determined the equivalent weights of a
large number or organic bases dissolved in glacial acetic
acid eith perchloric acid. Lone (dd) also reported the
determination of mercury (11) by the precipitation of
copper dipropylenediamine mercuric iodide. The precip-
itate was dissolved in glacial acetic acid and mercuric
acetate and titrated with perchloric acid in glacial
acetic acid. In the cane report Lane also describes the
determinations of some metal ions by chelation and
subsequent titration of the liberated hydrogen ions with
a standard solution of potassium methoxidc.

Young (62) titrated lithium halides and other salts
with a standard solution of silver nitrate in a pyridine
solution. he also reported that high frequency methods
can be used to determine alkali metal acetates by titra-
tion with perchloric acid.

Lippincott and Timnick (as) determined aniline,
substituted anilines, and mixtures of substituted anilines
in glacial acetic acid with a standard perchloric acid
titrant.

Karrman and Johaneson (38) used potassium methoxidc

in 10:1 benaene-methanol for the titration of nonohydroxy-,

dihydroxy-and trihydroxy phenols dissolved in benzene-
methanol or benzene-dimcthyl formemide. They also
reported that when mixtures of phenols were titrated,
each component gave a titration break in the order of
decreasing dissociation conatant.

81010 and Maroon (55) reported that titrations of
dihydrOphenazine with potassium diohronate in glacial
acetic acid gave sharp high frequency endpoints. They
also titrated organic bases dissolved in glacial acetic
acid with a standard pcrchloric acid solution (56).

Allen and co-workers (1) employed a Q-Meter for non-
aqueous titration of sulfonamidcs and the sodium and
potassium salts of organic acids.

Hera and test (22) successfully titrated a number
of organic acids, bases, and chelating grours in non-
aqueous solvents. Titrationa of lactic, tartaric,
succinic, citric, formic, or propionic acids dissolved
in pyridine with alcoholic potassium hydroxide were
carried out. The bases dissolved in glacial acetic acid

were titrated with pcrchloric acid.

EXPERIMENTAL

Reagents

The chemicals used in this investigation were not

repuriried unless otherwise noted. Repurification of the

organic acids was not considered necessary, since the

high frequency titrations were evaluated by comparing

these results with those obtained by conductimetric and

potentiometric titrations.

The compounds titrated, labeled purity, and source

are 8

Organic Acids:

Adipic acid
Citric acid
Fumaric acid
Haleic acid
Malonic acid
Oxalic acid
Phenol
Salicylic acid
Sebacic acid
Succinic acid
Vanillin

Recrystallised from acetic‘acid
Fisher, Certified Reagent
Practical

Eastman, practical

Dow Company

Reagent grads

Eastman White Label

Colemmn and Bell, C.P.
Eastman, Practical

Baker's Analysed Reagent
Retort Pharmaceutical, U.S.P.

Other chemicals used were:

Primary Standards:

Bensoic acid dried over

sulfuric acid

Potassium acid phthalate ovendried.for tso

Other Chemicals:

hours at 105°

Amberlite I.R.A.-4OO resin analyticalgrade
Tetrabutylammonium iodide fiatheson, Coleman

and Bell or
Eastman Kodak

10

Solvents: Benzene,“ C. P. and methanol, herck,
absolute were used as received. Bethyl
isobutyl ketone was freed of acid by
passing it through an activated alumina
column. Anhydrous isopropyl alcohol was
prepared by distillation from calcium
metal turningc. An ee-oe° boiling point
fraction was collected. ”imethyl fornamide
was purified by distillation.

Tetrabutylammonium.hydroxide in isopropyl alcohol nil
prepared by the method or hyld and co-aorkers (23). In
this method an AMberlite 1.8.A. ion exchange resin was
used to convert the tetrabutylammonium iodide to tetra-
butylammoniun hydroxide. The ion exchange column, 62
centimeters long, was made from 4 centimeter glass tubing.
The column was conditioned by passing slowly 10 liters of
l H potassium hydroxide through the column. The column
was then washed with 5 liters of distilled water followed
by 5 liters of anhydrous isopronyl alcohol. Seven
hundred milliliters of isopropyl alcohol containing 100
grams of tetrahutylanmoniun iodide were passed through
the column. The throughput was kept at a rate less than
5 milliliters per minute to insure maximum conversion to
the hydroxide form. Seven hundred milliliters of anhy-
drous isopropyl alcohol were then passed through the

column and these washings were combined with the reagent.

11

The 1400 milliliters of tetrahutylammonium hydroxide
were stored in a 2 liter pyrex bottle equipped with an
escsritooanhydrono absorption bUIb to insure maximum
reagent stability. Reagent.solution was withdrawn from
this bottle through an all-glass siphon.

The tetrabutylannonium hydroxide was standardised
against primary standard benzoic acid by'a visual titra-
tion procedure. Five drops of thymol blue dissolved in
isOpropyl alcohol was used as the indicator. methyl
isobutyl kctone or 80% benzene-20% methanol was used as
the solvent for the standardization. The indicator
blank for 50 milliliters of the solvents was less than
0.08 milliliters. To check the adequacy of thymol blue
as the standardization indicator, several potentiouetric
standardization titrations were performed. Coed agreement

between the two standardisation methods was observed,
Apparatus

A Ecckman Kodel B~2 p5 hater, equipped with a glass
eleatrode and a sleeve type saturated calomcl electrode
pair, was used for the potentiomctric titrations.

The conductance titrations were performed with a
Serfasa hodel ROE 15 Conductivity Bridge. Flatinizcd
platinum immersion electrodes (cell constant of 0.1) were
employed.

Preliminary high frequency titrations were conducted

with the high frequency titration apparatus designed and

12

constructed by Johnson and Tinnick (56). It was found,
howevcr, in the course of the preliminary titration:
curried out, that the apparatus was affectod at timee by
line voltage fluctuationc which resulted iu erratic
instrument rcsponee. To eliminate or greatly reduce
this erratic behavior a aocond stare voltage regulator
unit was incorporated in the circuit.

Figure 1 show: the circuit diagram of the modified
high frequency titration apparatus utilizing a R.C.A.
voltage regulator circuit. ihic voltage regulator
circuit (52) includes a 5651 voltage reference tube.
Only two major modifications were required for the adap-
tion of the voltage regulator circuit. Two voltage
reference tubes (typo 023) in curios were required to
supply the 300 volt Operation level of the second stage
voltage regulator. A potential divider at the output of
the regulated power supply was added to provide 150 volt-
to the 955 oscillator tube.

A new instrument, including the second stage voltage
regulator circuit, was constructed. Very stable instru-
ment cpcretion was attained. fly tests in which line
voltage to the instrurent was varied from 120 to 60 volts,
only very email changes in instrument response were
observed. Zhe real test of satisfactory stable perform-
ance was made during titratione. Vary little scattering

of points in the titration curve: was detected.

High Frequency Circuit Diagram Code
(Eor Figure 1)

0.. Cell assembly

61, Cg, Ca, C4. 133 micromicrofarads, mica
C5, C5. 20 microfarads, 450 volts

07. 0.1 microfarads, 400 volts

L1. HG E/U coaxial half-wave line, approximately 85
centimeters total length

L2. 10 turns No. 22 wire wound around R4

L3. Filter choke, Stancor C-1709, any, 85ma. DC.
Bl, R4. 15,000-ohm, 1-watt

R2. loco-ohm, l-watt

H5. loo-ohm, S-Iatto

R5. 12,030-ohm, 2-watts

85, R7. 4?,OOO-ohm, 0.5ouatta

R3. 12,000-ohm, 2-watts

R9. 68,000-ohm, 2-inch:

R10. 1,009,000-0hm, 0.5-wutts

R11. 15,0CO-Ohm, 2-watta

R12. 10,000-ohn output voltage-control potanttometer
813. 5000-0 m, wire wound

314. ISO-ohm, 10-watts, plate current balancing
potentiometer

T. 350-0-550, QOma.x 5 volts, 3:; 6.5 volts. 58.

V2. 5Y3

V3: V4. ODS. va lsq/so
V50 6AS7‘GT

V6. PSL7-GT
V7. 5651

 

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15

The operating frequency of the titration apparatus
was moanurod with 3 Signal Corps Signal Generator
Eodol l-ZEZ-A and Signal Lorpa Notorodyno flonitor
fiodoloBC-l755oA. Tho Operating frequency employed
throughout this study out 148.5 no.

A Sargant fiodol XXI Polarograph, connoctod across
n fixod resistor in series uith the grid leak resistor
of tho oscillator tuba, Ill used to detect grid current
charges (38).

The half-wave coaxial line and tho plate typo
capacitativo coll employed were flhoso constructed by
Hooaor (31).

A 250 milliliter polyethylene bottle was employed
as o titration vessel. A motor driven glass stirring
paddle oxtended through a amall hole in the cap of the
bottle. Continuous stirring was used throughout tho
titration. The tip of n semi-micro burst, extending
through a amnll hole in the shoulder or the bottlo, Ill
immersed in the solution being titrated. Through appro-
priate port: a nitrogen atmosphere could to maintained
in tho bottlo.

Tho rocponso curve for totrabutylammonium hydroxide
in the rclatively basic dimethyl formamide was obtained
with the solution in the vessel under a nitrogen atmos-
phere. A nitrogen atmosphero was not maintained nhilo
titration: in which methyl isobutyl ketono or bonzono-

mothnnol nerved as solvents.

16
Titration Procsduroo

Potontiomotrig Titrations

Tho weighsd ommplos IOPO dissolved in 50 milliliters
of oithor 805 bonsano-QOfi'mothnnol or methyl ioobutyl
kotono. The choics of the solvent depended on the
apparent acidity of the acid.

The standardization control on tho pH motor was
adjusted until the lowest pH valuo, usually one, was
indicated on the motor. Titrant'uaa added in 0.5 mil-
liliter incrcmonts to the stirred solution. Hear the
endpointrthc increments were reduced to 0.03 millilitor.

Some of the stronger dibasic acids could not be
titrated in methyl iaobutyl kctono using the godol 3-2
pH Motor, because the motor noodle went off scale before

tho titration was completed.

Conductimotric T trationa

Tho weighed samples were dissolved in 50 milliliters
of solvent. Titront was added through the buret tip
which was immoraod in the solution being titrated.
Conductance volues were moaaurcd during the course of the
titration with the oscillator or the conductivity bridge
Operating at 60 cycles per second.

A nitrogen atmosphcrc was maintained in the titra~
tion 708381 only while the rccponso curve was being

obtained for the dinothyl fornamido system.

17

High Freguencz Titretions
The high frequency titration apparatus and the

 

polsrozrspb eere sllosed to warm up for at least 15
minutes prior to titretions.

Weighed samples were introduced into the titration
vessel and dissolved in 150 milliliters of solvent.

Folsrogrepb edjustments were made so that the
recorder indicetor assumed some desirable initisl velue.
This was sttsined by selecting s 1.0 volt spen, s 20%
bridge setting and s sensitivity or 0.06 microemperes

 

per millimeter. Doenscsle compeneetion ees employed for
the final adjustment. when the indicator moved too fer
upscale during s titration, it was returned to the
initial value by adjusting the downscale compensator.
The reagent burst tip extended below the surfsce

of the solution being titrated. Reagent see added in

.25 to 0.50 milliliter measured portions. Instrument
readings were made 30 seconds after each portion of

reagent had been added.

18

{1
H
(’3
(‘1
’3
(.4
(x)
H
'J
«3
C)
ijfi
A
‘ a
L:
(—0
f—J
~ 1
U1

Instrument fiespon§g_Curves

To obtain the information for constructing response
curves. measured increments of titrsnt were added to a
known volume of solvent contained in the titration
vessel of the instrument being used. Instrument readings
for various concentrations were recorded.

High frequency and conductimetric response curves

a.

sore constructed by plotting the molar concentration of
the titrant in the solvent being studied against the
instrument readings. inosc curves served as useful
guides in the selection of suitable solvent-titrent
systems and of the Optimum concentration level in the
solution to be titrated. The test solvent-titrant system
is one ehich yields relatively high and lineer instrument
response for slight on ngss in concentration. The
optimum concentration level in the solution being titrated
is that which yields linear and relatively high instru-
ment response when the concentret on changes in the
solution.

Figure 2 shows the high frequency roeponse curves
for tetrebutylsmnonium hydroxide in 80% benzene-205 meth-
anol, methyl isobutyl ketone, and dimothyl fornsnido.

The greatest instrument response was obtained ehen the

9
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tetrabutylammonium hydroxide concentration was varied

in 80% benzene-20%.methsnol. Dimcthyl formamide as the
solvent gave the least instrument response, and thus was
not considered an adequate solvent for titrations vith
tetrabutylammonium.hydroxide.

For comparison purposes a conductimetric response
curve for tetrabutylammonium hydroxide in 80$ benzene-
20; methanol is included in Figure 2. The shapes of the
curves are similar. This is to be expected since high
frequency response is related to specific conductance.
Greater relative response was obtained with the high
frequency apparatus than with the conductimstric
apparatus in the concentration range 0.001 to 0.01 molar

totrabutylammonium hydroxide.
High Frequenc1_And Conductimetric Titration!

Monobssic égi§£_i§|lothzl Isobutzl Kctons

filtration of several weak and very weak acids
dissolved in methyl isobutyl kotone with tetrabutyl-
ammonium.hydroxide were performed by high frequency
titrimstric procedures. Very little change in slope at
the endpoint was observed for these acids. The acids
titrated were bensoic, salicylic, and phenol.

Several conductimetric titrations of benzoic acid
in methyl isobutyl kctona with tetrabutylammonium
hydroxide resulted in titration curves which vere compar-

able in shape to those obtained by high frequency methods.

21

The results of these titretions indicate the unsuit-
ability of using tetrahutylammonium.hydroxide as the
basic titrent for high frequency titrations of weak and

very weak nonobssic acids in methyl isobutyl ketone.

tonobssic Acids i§,Bensene~Methanol
High frequency and conductimetric titrations of
benscic acid in three different bensene~methsnol mixed

 

solvents indicate that 80% bensene-BO% methanol is the
best solvent for titrations conducted with tetrabutyl- é
ammonium hydroxide. Figure 3 shows the high frequency
titration curves obtained for bensoic acid dissolved in
50% benzene-50$ methanol, 80% benzene-20% methanol, or
90% benzene-10% methanol. The titration curve A,
Figure 3, indicates that relatively high.instrument
response was obtained when 50% benzene-50% methanol was
employed as the solvent. Conductimetric titrations of
bensoic acid conducted in these solvents clearly show
that the best defined endpoints were obtained for the
80% bensene-QOX methanol solvent. The Bofl'bensene-
zoflnethanol, therefore, was chosen as the solvent.for all
high frequency and conductimstric titrations conducted
in the remainder of this investigation.

Bensoic acid, salicylic acid, and vanillin dissolved

in benseneomethanole were successfully titrated with

 

GThroughout the remainder of this thesis the term benzene-
methanol refers to 80% bensene-ZOfi methanol solvent
unless otherwise stated.

 

 

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25

tetrabutylanmonium hydroxide by high frequency and
conductimetric titration methods. Figure 4. curve c,
shows the high frequency titration results obtained for
salicylic acid in this solvent.

i single conductance titration of phenol dissolved
in bensene-methanol with tetrabutylsmnoniun hydroxide
resulted in a poorly defined titration endpoint.

Polybasic m in denizens-methanol

Several dicsrboxylic acids were successfully titrated
in benzene-methanol with to trabutylammonium hydroxide.
The saturated dibssic acids titrated were adipic, malonic,
oxalic. sebacic, and succinic acids. The unsaturated
dibaeic acids titrated were fumaric and maleic acids.

the titration of dicarboxylic acids with tetrabutyl-
ammonium hydroxide resulted in distinct endpoints for
each carboxyl group present. fitration curves A and B
of Figure 4 show the results obtained for succinic and
sebacic acid respectively. Much sharper endpoints were
obtained for the shorter chain dicarboxylic acids than
for the longer chain members. An exception was maleic
acid. Very little change in the slaps of the successive
titration curve segments was observed for this acid.

Excellent firstlend second endpoints were obtained
in the high frequency titration of the tricarboxylic
citric acid. A slight indication of a third endpoint was

observed. Curve B of Figure 5 shows the complete
titration curve.

 

 

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26

or all the nonobasic and polyoasic acids titrated
with tetrebutylammonium hydroxide, adipic acid was the
only acid which fave a precipitate during the titration.
The precipitate, which formed before the first endpoint,
completely dissolved before the second endpoint was
reached.

The shapes of the conductinetric titration curves
for all of the polybaaio acids titrated were similar to

those obtained by the high frequency titration methods.
Potentiomotric Titrations

Potentiometric and conductimetric titrations were
performed to compare the results obtained by these
methods with those obtained by the high.frequency method.

By the potentiometric titration method the following
acids dissolved in methyl isobutyl kctone or benzene-
methanol sere successfully titrated with tetrabutyl-
ammoniunfihydroxide: adipic, benzoic, citric, fumaric.
maleic, malonic, oxalic, salicylic, sebccic, succinic,
and vanillin. Figure 6 shove the titration curves
obtained for adipic acid and malonic acid dissolved in
methyl isobutyl ketone and benzene-methanol respectively.
The potentiometric titration curve for citric acid is
shown by curve A of Figure 5. Only one good endpoint,
corresponding to the neutralisation of 2 equivalents of

citric acid, ... obtained.

 

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Comparison of Titration Results

To facilitate the intercomparison of titration
results obtained by high frequency, conductimetric, and
potentiomstrie titration methods, the titration results
for monobasic acids are tabulated in Table I and results
for the polybasio acids are tabulated in Table II.

In the discussion which follows, results obtained
by the high frequency or the conductimetric methods
agreeing within to; of the purity values obtained by
potentiometrio titretiono will be designated as good or
satisfactory results.

Very good high frequency titratione were obtained
for banzoic acid, salicylic acid, and vanillin in benzene-
methanol and for phenol in methyl isobutyl ketono.
methyl isobutyl kctone and benzene-methanol mixtures
other than the 801'benzene-20fl methanol are not satis-
factory solvents for the titration of bensoic acid.

Vethyl isobutyl ketone appears to be a satisfactory
solVent for the conductimetric titrations of benzoic
acid. The titration results for 5 trisls using the
benzene-methanol solvent were not in as good agreement
as those obtained by the high frequency method.

For all of the polybsoic acids titrated by the high
frequency and conductimetric methods, the second break
in the titration curve was more pronounced than the first

one. The difference in the sharpness between the first

29

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rr Rom.esumq coco oocunom
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31

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32

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vosndumou I HH Mdmdh

34

and second breaks in the titration curves is much greater
for the longer chain adipic end sebeoio acids. This fact
is demonstrated by comparing the percentage purity values
shown in Table II for each of these acids.

Satisfactory results, calculated on the basis of the
second neutralization endpoint, were obtained for adipic,
citric, fumaric, malonic, oxalic, sebscic, and succinic
acids. In nearly all cases, the conductimetric titration

results obtained for these acids were in good agreement I

 

with those obtained by the high frequency and poten— €

tiometric methods. ‘
with the exception of the results obtained for the

longer chain adipic and sebacic acids, the titration

results evaluated on the basis of the first titration

endpoint for high frequency and conductimetric titrations

sore satisfactory.

Titretiqg._£ Acid Kixtures

 

 

Very little change in the slaps of the successive
high frequency titration curve segments was observed for
maleie acid. Much sharper endpoints were obtained for
fumsric acid then for maleic acid. these results
suggested the possibility of resolving a mixture of these
acids. Figure 7 shows a typical high frequency titration
curve obtained for s titration of rumsric and meleic acid
mixture with tetrstutylammonium hydroxide. The results

are summarized in Zsble III.

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37

The volume of titrant added to attain the four
successive endpoints in the titration of the fumeric and
maleic acid mixture are designated by the letters
A, B, C, and D as shown in Figure 7. Considering sample
siae and shape or titration curves obtained for the
individual acids, the titration stage B-C should cor-
respond to the neutralization of 1 equivalent of
fumaric acid. Then the volume of titrant required to
neutralize the first equivalent or maleic acid could
be represented by C-2(C-B) milliliters. 0n the basis
of relative strengths of fumeric and maleic acids in the
aqueous system, it was concluded that points A and D
correspond to neutralisation of the first and second
carboxyl groups of maleic acid and points B and C
correspond to neutralization of the first and second
carboxyl groups or fumaric acid.

From the limited number of trials, it appears that
fumaric acid can be determined to 15% if approximately
1 milliequivalent of this acid is present in the mixture.
In trial 4,poorly defined breaks were obtained so that
no resolution was possible. The excessive curvature
probably resulted from the high concentration of fumsric
acid in the sample.

lbs total acid content, calculated for point D, in
the samples titrated for trials 1 to 4 were 38.8, 94.6,

94.0. and 97.573 respectively.

38

A single high frequency titration of a mixture or
salicylic and succinlc acid with tetrnbutylammonium
hydroxide resulted in an unsuccessful attempt at

resolving this mixture.

SLETKARY AND C C R C Li? 3 I 335!

The high frequency titration apparatus developed
by Johnson and Tinnick (36) eaa modified by introducing
a second stage voltage regulation unit to the instrunent
poser supply. Extremely stable performance with the F
instrument operating at 143.5 no was attained. ‘

I

Tetrabutylamonium eae tested as a aui table titrant

 

 

for high frequency titretions of acids dissolved in non- .
aqueous solvents. 0f the solvents tested, methyl isobutyl it
ketone, dimethyl fomnide, 503E; benzene-50f: methmcl,
803-2". bonanza-205$ no thanol, and 90:75 benzene-10$ me thanol,
the 805.1; comma-203$ methanol use the most satisfactory.
the high frequency titration results were compared
eith conductinctrio and potentiometric titration results.
Titration results and shapes of titration curves were
quite similar for the high frequency and the conducti-
metric aethods.
High frequency titration results, agreeing to £255;
eith corresponding potenticme trio results, were obtained
for the following nonobaslc acids dissolved in 80:31 hens-1e-
203’. methanol! beneoic acid, salicylic acid, and vanillin.
Three high frequency titrationa sore performed for
phenol dissolved in methyl ieobutyl ketone. The mean
value of 99.55% purity obtained in this study is in

excellent agreement with the mean 99.155 purity value

40

obtained by the brominetion method need by Hooeer (31)
for the cane phenol supply.

High frequency titration results, agreeing to iefi
with the purity values obtained by potentionetric
titration of acids dissolved in methyl ieobutyl kctone
or 80? benzene-£05 oethanol, were obtained for the
following polybasic acids dissolved in 895 benzene-

20% methanol: adipic, citric, fumaric, maleic, malonic,
oxalic, sobucic, and succinio acids. Two breaks in the
titration curvee were obtained for all of the dibaeic
acids titrated. Only two sharp breaks were obtained for
the tricsrboxcylic citric acid. The third break was
Very :oorly defined.

The two breoke in the titration curve for maleio
acid were not as sharp as those obtained for fumsric
acid. than a mixture of these two acids was titrated,
four breaks in the titraxion curves were obtained.
Fumaric acid content in a mixture res rosolved in three
trials to 15% purity. A fourth trial was unsuccessful.
Total acid content in the four mixtures was found to be
96.3 t2.5%._

A mixture of succinic and salicylic acids could not

be resolved.

1.

3.

4.

5.

6.

7.

8.
9.

10.

11.

12.

13.
14.

15.

16.

41

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Critchflold. F. E.. and Johnson, J. 8.. Ibid.. g3,
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Cundlff, R. H., and Markunaa, P. C.. Ibld., 3g. 792

.(1956)o

Deal, V. 2., and Wyld, G. k. A., Ibid., g1, 47
(1.355).
Dean, J. 3., and Cain, C. Jr., Ibid., 07, 212 {1355).

lo
DoVriao, J. E. Schlff. 3., and Gents, E. 3., Ibid.,
g1. 1914 (19555. ”“‘“

Durbotaki. A. J., J. Am. 011 Chemist's Soc...§§, 221
(1956).

Llloringbon, T., Nicholls, J. J.. Analyst, fig, 235
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48

17. Fickon, G. E., and Lane, E. 3., Anal. Chim. Acta,
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(£5. a (1955). . A. 5;. 125 (1557).

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(1356).

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Hare. 5., and West, P. 5., Anal. Chim. Acta, 15,
193 (1955). "*

ES

 

-—-u-'

r .‘x‘ lu‘J’fu

25. Harlow. G. A.. Noble, C. M.. and Wyld. G. h. A.,
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24. 1515.. g5, 754 (1955).

25, Earlow, G. A.. and fiyld, G. E. A., Ibid., g2, 69
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25. 1515.. 59, 73 (1555).

27. Henry, H. 0., Hazel J. F., and Ecfiabb, Anal. Chim.
Acta, 15. 157 (19553.

28. Higuchi, T., Foldman, J., and fiehm, C. R., Anal.
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30. 8111. C. H.. 151, 3., Underwood. A. L.. and
Day. R. A. Jr.. Ibid., §§. 1688 (1956).
31. Boozer, 3., Unpublished Master‘s Thesis, fitchigan
ftato)University of Agriculture and Applied Science,
1956 .

52. Ishidnto, M., and Masui, 5., Pharm. Eull. (Japan),
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33. Jander, V. 6., and Klaus. H., J. Inorg. and Nuclear
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Anal. ado, 1-8., 535 (1.946).

43

55., Jahnaon' J. 13., and) Funk, Go Ln. filnalo C115m.' 2-9.,
1977 (1555).

56. Johnson, A. H., and Tlmnick, A., Ibid., fig, gag
(1356). ‘“"

57. liarczhmer, J. (1., 1515., g1, 4:25 (1957).

38. Earrman, K. J., and Johanaaon, 6., Hikrochim. Actg,
1575 (1555).

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40. 1515.. 15. 586 (1555). C. A. 53, 12775 (1955).

41. Eilpatrick, 2.. Am. Soc. iestlng Materials, Spec.
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42. Kolthoff, I. E., Exparientia Sappl. fig, 5, 55
(1355). c. 5. 51. 7222 (1957 . .

 

45. Lane, 5. 5., Analyst, 59, 675 (1955).
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.45. Liebor. 8.. R30, C. E}. 3.. find C1180, T. 50’ Anal.
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46. Lippincott, W. 1., and Tinnick, A., Ibid., gg, 1590
(13:5). "“"“‘

47. malmstadt, 5. v... Putt, 1;. 5.. 1515., g, 1757 (1955).
48. martin, A. J., Ibid., g2, 73 (1657).

49. Kizukami, 5., and fitrai, 3., Ann. Rept. Shionogl
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50. Eizukami, 3., and Hiral, 1., Yakugaku Zasshi, 21,
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52. "Radiotron Designer's Handbook,” Fourth Edition,
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53. Rahm, 5., and Higuchi, 1., Anal. Chem., 23, 367
(1957). "'

 

56.
67.

58.

59.
60.

61.

62.

V Riddick, J. A., Ibid., Qg, 673 (1956).

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293 (1955).

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Van er “0156.. Ho Be, .115 DflhmOn. E. A. ”a 1". An.lo
Chm. Acta, 2.3, 573 (1957).

East, '1‘. 3., Chem. Age, 1g, 114:5 (1955).

Young, J. P.. Dessert. Abstr., 1g. 1308 (1955).

 

Rate: A. A. - Analytical Abstracts

 

CHEMISTRY mama?
Date Due

 

 

Demco-293

DWI-I ma
‘ JiihLMJS'IRY LILBAHY
Thesis

0.1 FleCk’

High frequency titration of some -
monobasic and dibaSic acids in N
non-aqueous media.

M.S. 1958

CREME”? luau
Thesis Y m

0.1 Fleck,

High frequency titaatihn 0! some
monobasic and dibaaic acids in
non-ggggous mefiia. M.S. }§§§__

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ISSUED TO
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