Packaging and storage—
Preserve in well-closed containers.
Identification—
Place 20 mL of the saponified solution obtained in the determination of
Esterified carboxyl groups in a 250-mL conical flask, add 50 mL of a solution of periodic acid (1 in 50), swirl, and allow to stand for 30 minutes. Add 2 g of potassium iodide, titrate with
sodium thiosulfate TS to a faint yellow color, dilute the mixture with water to 200 mL, and mix to obtain the test solution for tests
A and
B.
A:
Dissolve 200 mg of rosaniline hydrochloride, C
20H
20ClN
3, in 120 mL of hot water. Cool, add 2 g of sodium bisulfite, NaHSO
3, followed by 2 mL of hydrochloric acid, and dilute with water to 200 mL to obtain modified Schiff's reagent. (Store this solution in a brown bottle at 15
or lower.) To 10 mL of the test solution add 5 mL of hydrochloric acid and 10 mL of modified Schiff's reagent: a blue to blue-violet color, due to formaldehyde, develops in about 20 minutes.
B:
To 10 mL of the test solution add 1 mL of a saturated solution of piperazine and 0.5 mL of
sodium nitroferricyanide TS: a green color, due to acetaldehyde, develops.
Microbial limits 
61
—
The total bacterial count does not exceed 200 cfu per g, and the tests for
Salmonella species and
Escherichia coli are negative.
Loss on drying 731—
Dry it at 105
for 4 hours: it loses not more than 20.0% of its weight.
Ash—
Weigh accurately about 3 g in a tared crucible, and incinerate at 650 ± 25
until free from carbon. Cool in a desiccator, weigh, and determine the weight of the ash: not more than 10.0%, calculated on the dried basis, is found.
Lead 251—
Add 1.0 g to 20 mL of nitric acid in a 250-mL conical flask, mix, and heat carefully until the specimen is dissolved. Continue the heating until the volume is reduced to about 7 mL. Cool rapidly to room temperature, transfer to a 100-mL volumetric flask, dilute with water to volume, and mix. A 50.0-mL portion of this solution contains not more than 5 µg of lead (corresponding to not more than 0.001% of Pb), 15 mL of ammonium citrate solution, 3 mL of potassium cyanide solution, and 0.5 mL of hydroxylamine hydrochloride solution being used for the test. After the first dithizone extractions, wash the combined chloroform layers with 5 mL of water, discarding the water layer and continuing in the usual manner by extracting with 20 mL of 0.2 N nitric acid.
Heavy metals, Method II 231:
0.004%, a platinum crucible being used for the ignition, and nitric acid being used in place of sulfuric acid to wet the test specimen.
Free carboxyl groups—
Transfer about 1 g, accurately weighed, to a 600-mL beaker. Dissolve in 200 mL of water, stirring by mechanical means for not less than 30 minutes, and titrate with 0.1 N sodium hydroxide VS to a pH of 7.0, determining the endpoint potentiometrically. Calculate the weight, in g, of free carboxyl groups in the weight,
W, in g, of specimen taken by the formula:
0.0044V / W,
in which
V is the volume, in mL, of 0.1 N sodium hydroxide consumed: the weight of free carboxyl groups found, calculated on the dried basis, is not more than 35% of the weight of carbon dioxide yielded by an equal weight of specimen in the
Assay.
Esterified carboxyl groups—
Transfer the solution obtained in the test for
Free carboxyl groups with the aid of water to a 1000-mL conical flask, add
phenolphthalein TS and 50.0 mL of 0.1 N sodium hydroxide VS, insert a stopper in the flask, mix, and allow to stand for 30 minutes at ambient temperature. Titrate the excess sodium hydroxide with 0.1 N hydrochloric acid VS to a faint pink endpoint. Transfer the solution with the aid of water to a 600-mL beaker, and complete the titration to a pH of 7.0, determining the endpoint potentiometrically. Calculate the weight, in g, of esterified carboxyl groups in the weight,
W, in g, of specimen taken by the formula:
0.0044v / W,
in which
v is the volume, in mL, of 0.1 N sodium hydroxide consumed: the weight of esterified carboxyl groups found, calculated on the dried basis, is between 40% and 85% of the weight of carbon dioxide yielded by an equal weight of specimen in the
Assay.
Assay—
Proceed as directed for
Procedure under
Alginates Assay 311, without preliminary drying of the Propylene Glycol Alginate.
