determination of anthranilic acid and...

CHAPTER IV

DETERMINATION OF ANTHRANILIC ACID AND ~AL

ANTHRANILATES WITH DIBROMAMlNE-T

Very recently, Nair and Indrasenan have introduced

dibromamine-T as an oxidimetric titrant in acetic acid

d . 46me· ~um • These workers carried out potentiometric and

visual indicator titrations, using dibromamine-T in acetic

acid as titrant, for the determination of substances such

as As(III), Sb(III), Tl(I) and oxine and metallic oxinates

(cf Table 1). The successful determination of oxine and

metallic oxinates with dibromamine-T led us to examine

the possibility of determining antrJanilic acid and metal

antrJanilates by a similar procedure ••

Anthranilic acid has a number of industrial uses,

for example, in the manufacture of dyes, drugs, perfumes and

pharmaceuticals. Its analytical determination is of con-

siderable practical interest. It is conventionally determined.

by an excess-back titration method using potassium bromate

in aqueous hydrochloric acid medium iII presence of bromide9 .

119

This method, while applicable to metal anthranilate5 also,

has the disadvcmtage that it is time-consuming and that

errors due to loss of bromine are likely. Moss and co-

k 150". dId . d· b . . . ..wor ers Have eve ope a nonaqueous aCl - ase ~l~ra~lon

procedure for the determination of antr~anilic acid, using

sodium 2-amino ethoxide as the base and ethylenediamine as

the solvent. In this chapter a simple redox titrimetric

method is described involving the direct potentiometr:i.c or

visual indicator titration of antr~anilic acid and metal

antr~anilates in a mixed aqueous-acetic acid medium. Dibro-

mamine-T in anhydrous acetic acid is used as a titrant, where-

as the titrate (anthranilic acid or metal antr~anilates) is

taken in an aqueous hydrocruoric acid mediu~, in presence of

added bromide ions.

EXPERIMENTAL

Dibromamine-T was prepared by the bromihation of

chloramine-T as described in Chapter II. Stock solutions

were prepared, standardised and stored out of contact with

moisture and light as described in chapter II.

Procedure for potentiometric titrations

Measured aliquots (5 to 15 ml) of solutions of

antr~anilic acid (or metal antr~anilates) in 4! hydrochloric

acid were taken in the titration cell. Acetic acid (25 ml)

and OQ5-1 g potassium bromide were added. The solution was

diluted to 50 ml with distilled water and titrated with

standard dibromamine-T solution, added from a microburette.

Procedure for titrations using organic dyestuffs as visual

indicators.

The following 6 indicators were tried: qUinoline

yellow, p-ethoxyct~ysoidine, bordeaux, amaranth, methyl red

and methyl orange. Of these, qUinoline yellow was found to

be the best. To measured aliquots (5 to 15 ml) of the re

ductant solutions, 0.5-1 g of potassium bromide and 2-3 drops

of the indicator (quinoline yellow) were added. The solu-

tions were diluted to about 100 ml with water and was titrated

against standard dibromamine-T solution until the yellow

colour of the solution just got discharged. The oxidant con

sumptions of the indicator was found to be only one drop.

Therefore, the blank correction amounted to one drop (~0.02 ml).

RESULTS AND DISCUSSION

Typical results including statistical data are given in

Tables 51 to 66 and typical potentiometric titration curves

(E ~ V and ~E/ tlV Ie V) are presented in figures 8 to 14.

The results show that both potentiometric and visual indicator

methods are reasonably accurate.

TABLE 51

DETERMINATION OF ANTHRANILIC ACID WITH DIBROMAMINE-T

(POTENTIOMETRIC TITRATION)

Expt.No.

Anthranilicacid takenmmol-

Dibromamine-Tconsumedmeg

Equivalents ofDibromamine-Tconsumed permole of anthranilic acid

Anthranilicacidfound*mmol-

Error%

---------------------------------------------------------------------------------------1- 0.1950 1.166 5.981 0.1944 - 0.31

2. ,0.2340 1.409 6.020 0.·2347 + 0~30

3. 0.2145 11285 5.991 0.2141 - 0.19

4. 0.2534 1.520 5.998 0.2533 - 0.04

5. 0.2730 1.644 6.022 0.2739 + 0.33

6. 0.2925 1.755 5.999 0.2924 - 0.03

-------------------------------------~------------------------------------------------~

*Assuming that 6 equivalents of oxidant are consumed per moleof antrJanilic acid.

-"I\)

-"

TABLE 52

DETERMINATION OF MANGANESE ANTHRANILATE WITH DIBROMAMINE-T


Exp1i.No.

Manganesean tr.LZ'anilatetakenmmol


Equivalents ofdibromamine-Tconsumed permole of manganese anthranilate

Manganeseanthranilatefound*mmol

Error

%

------------------------------------------------------------------------------------------1- 0.04588 0.5487 11.96 0.04573 - 0.33

2. 0.08177 0.9860 12.06 0.08217 + 0.49

3. 0.09434 1.124 11.91 0.09365 - 0.73

4. 0.1258 1.508 11.99 0.1256 - 0.16

5. 0.1572 1.891 12.03 0.1576 + 0.25

6. 0.1887 2.271 12.03 0.1892 + 0.27

------------------------------------------------------------------------------------------*Assuming that 12 eqUivalents ·of oxidant are consumed

per mole of manganese antt.LZ'anilateo ->1\)N

TABLE 53

DETERMINATION OF COBALT ANTHRANILATE WITH DIBROMAMINE-T


---------------------------------------------------------------------------------------------Expt.

No.Cobalt ant:branilate takenmmol-


Equivalen ts ofdibromamine-Tconsumed permole of cobaltanthranilate

Cobaltantr!Xanilatefound*mmol

Error%

---------------------------------------------------------------------------------------------1- 0.03930 0.4715 11.99 0.03929 - 0.03

2. 0.0525 0.6308 12.01 0.0525 0.00

3. 0.06545 0.7845 11.98 0.06537 - 0.12

4. 0.08030 0.9658 12.02 0.08040 + 0.12

5. 0.0937 1.120 11.95 0.0933 - 0.43

6. 0.1064 1.287 12.09 0.1072 + 0.75

----------------------------------------------------_.-----------------------------------------*Assuming that 12 equivalents of oxidant are consumed per mole of cobalt anthranilate.

->i'J

\..>-1

TABLE 54

DETERMINATION OF NICKEL ANTHRANILATE WITH DIBROMAMINE-T


------------------------------------------------------------------------------------------Expt. Nickel anthra-

No. nilate taken.!!!!!21


Equivalents ofdibromamine-Tconsumed permole of nickelanthranilate

Nickel ant"hranilate found*

Error%

------------------------------------------------------------------------------------------1 • 0.06507 0.7809 12.00 0.06507 0.00

2. 0.07045 0.8502 12.06 0.07085 +0.67

3. 0.1081 1.294 11.97 0.1078 -0.28

4. 0.1232 1.476 11.98 0.1230 -0.16

5. 0.1465 1 0 758 12.00 0.1465 0.00

6. 0.1823 2.184 11.98 0.1820 -0.16

-------------------------------------------------------------------------------------------*Assuming that 12 equivalents of oxidant are

consumed per mole of nickel anthranilate.

~

1'(1.p.

TABLE 55

DET~lINATION OF COPPER ANTHRANILATE WITH BIBROTh~MINE-T


Expt.No.

Copper antt!Xanilate taken1!!l!lQl


Equivalents ofdibromamine-Tconsumed permole of copperanthranilate

CopperanttlXanilatefound*~

Error~~

----------------------------------------------------------------------------------------1 • 0.07390 0.8824 11090 0.07329 - 0.83

2. 0.08860 1.0552 11.91 0.08785 - 0.85

30 0.1048 1.263 12.06 0.1054 + 0.57

4. 0.1201 1.452 12.09 0.1210 + 0.75

5. 0.1340 1.7370 12.97 0.1336 - 0.30

6. 0.1483 1.787 12.05 0.1490 + 0.43

----------~-----------------------------------------------------------------------------

*Assuming that 12 equivalents of oxidant are consumed per mole ofcopper antt~anilate.

-"f\.)

VI

TABLE 56

DETERMINATION OF ZINC ANTHRANILATE WITH DIBROMAMINE-T


-----------------------------------------------------------------------------------------Expt.No.

Zinc anttJXanilate taken~

Dibromamine-Tconsumedmeg·

Equivalents ofdibromamine-Tcons~med permole of zincanthranilate

Zinc anttJXanilatefound*mmol-

Error%

-----------------------------------------------------------------------------------------1• 0.04907 0.5887 11.99 0.04906 - 0.02

2. 0.05770. 0.6921 11.99 0.05767 - 0.05

3. 0.0665 0.7980 12.00 0.0665 0.00

4. 0.07307 0.8759 11.98 0.07299 - 0.10

5. 0.1069 1.274 11.91 0.1061 - 0.75

6. 0.1501 1.805 12.02 0.1504 + 0.20

-------------------------------~-----------------------------------------------------------

*Assuming that 12 equivalents of oxidant are consumed permole of zinc anthranilate

--'f'\)<:l'

TABLE 57

DETERMINATION OF CADMIUM ANTHRANILATE WITH DIBROMAMINE-T


------------------------------------------------------------------------------------------Expt.

No.Cadmiumanthranilatetakenmmol-

Dibromamine-T .consumedmeg

Equivalents ofdibromamine-Tconsumed permole of ·cadmiumanthranilate

Cadmiumantr..ranilatefound*J!ll!12!

Error%

----------------------------------------------------------------------------~-------------

1• 0.06709 -0.8051 12.00 0.06709 0.00

2. 0.08060 0.9662 11.98 0.08051 -0.11

3. 0.09509 1.141 11.99 0.09508 -0.01

4. 0.1083 1.296 11.96 0.1080 -0.28

5. 0.1209 .1.451 12.00 0.1209 0.00

6. 0.1342 1.617 12.04 0.1347 +0.37

------------------------------------------------------------------------------------------*Assuming that 12 equivalents of oxidant are consumed per mole of

cadmium anthranilate.

->f\)

--J

TABLE 58

ST~TISTIOAL DATA FOR TITRATIONS WITH BIBROlfillMINE-T

(POTENTIOMETRIO TITRATIONS)

------------------------------------------------------ ----------------------~------------

Reductant No. of experiments done

Relative meandeviation

Standarddeviation

Coefficient ofvariation

-----------------------------------------------------------------------------------------Anthranilic acid

Manganese antr~a

nilate

Oobalt anthranilate

Nickel antr...ranilate

Copper anthranilate

Zinc antra-anilate

Oadmium antrJXanilate

6

6

6

6

6

6

6

0.3103

0.3701

0.2500

0'.1900

0.6201

0.2103

0.1200

4.246x10-3

4.551X10-3

3.907x10-3

3.015x10-3

7.216x10-3

3.253x10-3

2.133x10-3

0.4250

0.4552

0.3907

0.3015

0.7218

0.3257

0.2133

-------------------------------------------------------------------------------------------->I\)

OJ

>1000E

i!;gooIUUIII

~800...eaI.

700

600

500

------.-----.. -- ------------- --

ANTHRANILIC Ar.ID v. OlBROMAMINLT

900

00

129

------- -._------._------------MANGANESE ANTHRANILATE Va OIBROMilMINE: _T

1000

~a!; goOUJUIII

~8oo

!

2.100

2.100

1800

600

400

3 3.5 4 4.5 5 5.5VOLLME OF Dl8ROMAMINE-T IN ml

FIG.S

400

6.5 7 ~ 8 ~ 9VOLUMEOFOIBROMAMINE.T IN ~I

FIG. 9

>1E

~

.... 900<)

III

:l!ooo...E0;700

600

500

3

COBALT ANntrANILATE V. ·OltlROMAMINE _T

3.5 4 4.5 5 5.5VOLUME OF OIBROMAMINE.T IN ml

RIO. 10

6

600

500

400

4

NICKEL ANTHRANILATE V. 'oI8lloMAMINE'_T

4.5 5 5.5 6 6.5VOLUME OF OIBROMAMINE.TIN ml

FIG. "

1800

><I

1500 ~<I

1200

600 ,

130

>1000E

ill 900III

'"VI

~800

toj 700

600

3.5

COPPER ANTHRANILATE V. 018ROMAMINE _T

4.5 5 5.5 6VOLUME OF OUIROMAMINE.T IN

FIG. 12

....,

3000

2700

2400

2100 1000

lleoO ~ ;;e900

......~III

<l

1500 ~ eoo

~1200

Ii700

900 600

600 500

300 400

4 4.5 5 5.5 6 6.5VOLUME OF DI8ROMAMINE.T IN

FIG.13

400

2100

18(1()

~\500 ;;;.

<I

1200

900

300

looe~~900III

~

:J 800

i..700

600

500

400

CADMIUM ANTHRANILATE \Is DlllAOMAMINE.T

2700

2400

2100

800>.:t

1500':1

1200

100

2.5 3 3.5 4 4.5 5\/OlUM£ Of DI8ROMAMINE _TIN ..I

FIG. 14

TABLE 59

DET~IINATION OF ANTHRANILIC ACID WITH DIBROMAMINE-T

(DIRECT TITRATION USING VISUAL INDICATOR)

------------------------------------------------------------------------------------------Expt. Anthranilic

No. acid taken~

Dibromamine-Tconsumedmeq

'Equivalents ofdibromamine-Tconsumed permole of anttiI'anilic acid.

AnttiI'anilicacid found*mmol-

Error%

Indicator

---------------,---------------------------------------------------------------------------1• 0.2060 1.2,0 5.970 0.2050 -0.49 Quinoline

yellow

2. 0.2460 1.490 6.056 0.2483 +0.93 "

3. 0.2265 1.365 6.020 0.2275 +0.44 "

4. 0.2634 1.580 5.990 0.2633 -0.04 "

5. 0.2785 1.684 6.040 0.2806 +0.75 "

6. 0.3025 1.825 6.030 0.3041 +0.53 If

-------------------------------------------------------------------------------------------

*Assuming that 6 equivalents of oxidant are consumedper mole of anttiI'anilic acid. ->

\>l->

TABLE 60

DETERMINATION OF MANGANESE AN THRANILA TE WITH DIBROMAMINE-T


Expt. ManganeseNo. anthranilate

takenmmol-


Equivalents ofdibromamine-Tconsumed permole of Manganese anthranilate

Manganeseanthranilatefound*mmol-

Error%

Indicator

----------------------------------------------------------------------------------------1- 0.4688 0.5607 11.96 0.04672 - 0.34 QUinoline

yellow.

2. 0.08287 0.9990 12.05 0.08325 + 0.46 "

3. 0.1044 1.244 11.91 0.1036 - 0.77 II

4. 0.1368 1.638 11.97 0.1365 - 0.22 II

5. 0.1682 2.019 12.00 0.1682 0.00 II

6. 0.1997 2.401 12.02 0.2000 + 0.15 "----------------------------------------------------------------------------------------*Assuming that 12 equivalents of oxidant are consumed per mole of

manganese anthranilate.

.....\.>Jf\)

TABLE 61

DETERMINATION OF COBALT ANTHRANILATE WITH DIBROMAMINE-T


Expt.No.

Cobalt anttlXanilate takenmmol


Equivalents ofdibromamine-Tconsumed permole of cobaltantrlXanilate

Cobaltanthranilatefound*mmol

Error%

Indicator

----------------------------------------------------------------------------------------

1- 0.04930 0.5935 12.03 0.04945 +0.30 Quinolineyellow

2. 0.06250 0.7508 12.01 0.06250 0.00 II

3. 0.07645 0.9100 11.90 0.07583 -0.81 "

4. 0.09130 1.0878 11.91 0.0906 -0.77 "

5. 0.1037 1.240 11.95 0.1033 -0.39 II

6. 0.1174 1.417 12.06 0.1180 +0.51 II

----------------------------------------------------------------------------------------*Assuming that 12 equivalents of oxidant are consumed per

mole of cobalt anthranilate.-"\.>l\.>l

TABLE 62

DETERMINATION OF NICKEL ANTHRANILATE WITH DIBROMAMINE~T


--------~--------------------------------------------- -----------------------------------

Expt.No.

Nickel antt~a

nilate taken!!1E!21


Equivalents ofdibromamine-Tconsumed permole of nickelanthranilate

Nickel Errorantt~anilate %found*mmol

Indicator

-----------------------------------------------------------------------------------------

2. 0.08145 0.9850 12.09 0.08208

3. 0.1190 1~424 11.96 0.1186

4-. 0.1340 1.596 11.91 0.1330

5. 0.1575 1.888 11.98 0.1573

6. 0.1943 2.344 12.06 0.1953

1 • 0.07507 0.9018 12.01 0.7515 +0.11 Quinolineyellow.

+0.80 II

-0.34 "

-0.75 II

-0.13 II

+0.51 II

------------------------------------------------------------------------------------------*Assuming that 12 equivalents of oxidant are consumed per mole ofnickel antr~anilate.

-"'JJ.e,.

TABLE 63

DETEIDHINATION OF COPPER ANTHRANILATE WITH DIBR01~MINE-T


Expt.No.

Copperantb.ranilatetakenmmol


Equivalents ofdibromarnine-Tconsumed permole of copperanthranilate

Cobaltanthranilatefound*mmol-

Error10

Indicator

------------------------------------------------------------~----------------------------

1- 0.08390 1.00008 11.92 0.08329 - 0.73 Quinolineyellow.

2. 0.09960 1.1862 11.91 0.09885 - 0.75 II

3. 0.1148 10384 12006 0.1154 + 0.52 "

4. 0.1301 1.5'71 12.08 0.1310 + 0.69 "

5. 0.1440 10733 12.04 0.1445 + 0.35 "

6. 0.1583 1.20'750 12.05 0.1590 + 0.44 "

------------------------~----------------------------------------------------------------

*Assuming that 12 equivalents of oxidant are consumed per moleof copper anthranilateo

-'\jJ

V1

TABLE 64

DETERMINATION OF ZINC ANTHRANILATE WITH DIBROMAMINE-T

(DIRECT TITRATION USI~G VISUAL IWDICATOR)

----------------------------------------------------------------------------------------._-Expt.

No.Zinc anthranilate takenmmol

Dibromamine-Tconsumedme!

Equivalents ofdibromamine-Tconsumed permole of ZincantrJXan ilate

Zinc anthra- Errornilate %found*mmol

Indicator

1• 0.06007 0.7187 11.96 0.05989 -0.30 Quinolinepllow.

2. 0.06870 0.8271 12.03 0.06892 +0.32 11

3. 0.07750 0.9280 11.97 0.7733 -0.22 11

4. 0.08507 1.0159 11.94 0.8465 -0.49 11

5. 0.1179 1.4230 12.06 0.1185 +0.51 11

6. 0.1613 1.945 12.05 0.1620 +0.43 11

--------------------------------------------------------------------------------------------*Assuming that 12 eqUivalents of oxidant are consumed

per mole of zinc anthranilate. -'\),JQ"\

TABLE 65

DETERMINATION OF CADMIUM ANTHRANILATE WITH DIBRON~MINE-T


--------------------------------------------------------------------------------------------Expt.

No.Cadmiumanthranilatetakenmmol-


Equivalents ofdibromamine-Tconsumed permole of cadmiumantt!I'anilate

Cadmiumantt!I'anilatefound*mmol

Error Indicator%

-------------------------------------------------------------------------------------------

2. 0.09160 1.0962 11 .96 0.09135

3. 0.1060 1.281 12.08 0.1067

4. 0.1193 1.426 11095 0.1188

5. 0.1320 1.588 12.03 0.1323

6. 0.1442 1.730 11.99 0.1442

1 0 0.07809 0.9351 11.97 0.07792 - 0.22 Quinolineyellow.

- 0.27 "

+ 0.66 "

- 0.42 "

+ 0.23 II

0.00 II

---------------------------------------------------------------------------------------------*Assuming that 12 eqUivalents of oxidant are consumed per mole of

cadmium anttJanilate. ~

~

~

TABLE 66

STATISTICAL DATA FOR TITRATIONS WITHDIBROMAMINE-T

(DIRECT TITRATIONS USING VISUAL INDICATOR)

Reductant No. of experiments done

Relative meandeviation

Standarddeviation

Coefficient ofvariation

-------------------------------------------------------------------------------------------Anthranilicacid

Manganesean thranilate

Cobalt anttlXanilate

Nickel anttlXanilate

Copper anthranilate

Zinc anthranilate

Cadmium anthranilate

6

6

6

6

6

6

6

0.4089

0.3204

0.4610

0.3203

0.5600

003700

0.3000

5.281x10-3

4.253x~0-3

5.526x10-3

4.309x10-3

6.598x10-3'\.

4.272x10-3

;.968x10-3

0.5266

0.4259

0.5538

0.431;

0.6598

0.4272

0.3969

--------------------------------------------------------------------------------------------~

~

rn

139

In preliminary experiments, titrations were tried in

the absence of added bromide ions. These were unsuccessful.

There was some consumption of the oXidant, but even when

excess-back titrations were tried, there was no stoichio

metric oxidation. In presence of bromide ions, however, the

reaction proceeded smoothly and fast.

The reaction involved here is obviously the bromi

nation of anthranilic acid. Therefore, the presence of

bromide ion is essential. Bromine is produced in~ by

the oxidation of bromide ions with dibromamine-T. Six equi

valents of the oxidant are consumed per antr~anilic acid

molecule which conforms to the following reaction scheme:

•• (41)

Thus 12 equivalents of the oxidant are consumed per mole of

the antr~anilates of Mn(II), Co(II), Ni(II), Cu(II),

Zn(II) and Cd(II). The potential jumps at the equivalence

points are of the order of 280 mV for the addition of 0.1 ml

of 0.2N dibromamine-T, in all the cases o

These direct potentiometric methods and visual methods

are more convenient than the conventional bromate-bromide

method. The conventional bromate-bromide procedure (-where

the aliquot of antr~anilic acid solution is added to an

excess of bromate-bromide mixture and acidified and kept

140

aside for 5 min, after which the unconsumed oxidant is

iodometrically determined-), there is always the possi

bility of some errors due to loss of bromine by volatili

zation. In the direct titrimetric procedures described

here, bromine is consumed as and when it is produced. Loss

of bromine is here ipso facto precluded.

determination of anthranilic acid and...

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