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
(POTENTIOMETRIC TITRATION)
Exp1i.No.
Manganesean tr.LZ'anilatetakenmmol
Dibromamine-Tconsumedmeg
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
(POTENTIOMETRIC TITRATION)
---------------------------------------------------------------------------------------------Expt.
No.Cobalt ant:branilate takenmmol-
Dibromamine-Tconsumedmeg
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
(POTENTIOMETRIC TITRATION)
------------------------------------------------------------------------------------------Expt. Nickel anthra-
No. nilate taken.!!!!!21
Dibromamine-Tconsumedmeg
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
(POTENTIOMETRIC TITRATION)
Expt.No.
Copper antt!Xanilate taken1!!l!lQl
Dibromamine-Tconsumedmeg
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
(POTENTIOMETRIC TITRATION)
-----------------------------------------------------------------------------------------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
(POTENTIOMETRIC TITRATION)
------------------------------------------------------------------------------------------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
(DIRECT TITRATION USING VISUAL INDICATOR)
Expt. ManganeseNo. anthranilate
takenmmol-
Dibromamine-Tconsumedmeq
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
(DIRECT TITRATION USING VISUAL INDICATOR)
Expt.No.
Cobalt anttlXanilate takenmmol
Dibromamine-Tconsumedmeq
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
(DIRECT TITRATION USING VISUAL INDICATOR)
--------~--------------------------------------------- -----------------------------------
Expt.No.
Nickel antt~a
nilate taken!!1E!21
Dibromamine-Tconsumedmeg
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
(DIRECT TITRATION USING VISUAL INDICATOR)
Expt.No.
Copperantb.ranilatetakenmmol
Dibromamine-Tconsumedmeg
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
(DIRECT TITRATION USING VISUAL INDICATOR)
--------------------------------------------------------------------------------------------Expt.
No.Cadmiumanthranilatetakenmmol-
Dibromamine-Tconsumedmeq
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.