CHAPTER IV DETERMINATION OF ANTHRANILIC ACID AND ANTHRANILATES WITH DIBROMAMlNE-T Very recently, Nair and Indrasenan have introduced dibromamine-T as an oxidimetric titrant in acetic acid d . 46 me· • 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 bromide 9 .
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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
----------------------------------------------------_.-----------------------------------------*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
------------------------------------------------------------------------------------------*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
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
------------------------------------------------------------------------------------------*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
---------------------------------------------------------------------------------------------*Assuming that 12 eqUivalents of oxidant are consumed per mole of