Packaging and storage—
Preserve in tight containers.
Identification—
A:
Chloride 
191
—Yields white, curdy precipitate of silver chloride with
silver nitrate TS, which is insoluble in nitric acid. After being washed with water, this precipitate is soluble in a slight excess of 6 N ammonium hydroxide.
B:
It meets the requirements of the test for
Manganese 191.
pH 791:
between 3.5 and 6.0, 10 g dissolved in 200 mL of carbon dioxide- and ammonia-free water being used.
Loss on drying 731—
Dry it at 50
for 2 hours, then raise the temperature to 150
for 24 hours: it loses between 36.0% and 38.5% of its weight.
Insoluble matter—
Transfer 10 g to a 250-mL beaker, add 150 mL of water, cover the beaker, and heat to boiling. Digest the hot solution on a steam bath for 1 hour, and pass through a tared, fine-porosity filtering crucible. Rinse the beaker with hot water, passing the rinsings through the filter, and finally wash the filter with additional hot water. Dry the filter at 105
: the residue weighs not more than 0.5 mg (0.005%).
Sulfate 221—
A 2.0 g portion shows no more sulfate than corresponds to 0.10 mL of 0.020 N sulfuric acid (0.005%).
Substances not precipitated by ammonium sulfide—
Dissolve 2.0 g in about 90 mL of water, add 5 mL of ammonium hydroxide, and warm the solution to about 80
. Pass a stream of hydrogen sulfide through the solution for 30 minutes. Dilute with water to 100 mL, mix, and allow the precipitate to settle. Decant the supernatant through a fine-porosity filter, and transfer 50.0 mL to an evaporating dish that previously has been ignited and tared. Evaporate the filtrate to dryness, cool, add 0.5 mL of sulfuric acid, heat gently to remove the excess acid, and ignite at 800 ± 25
for 15 minutes: the weight of the residue is not greater than 2.0 mg (0.2% as sulfate).
Iron 241—
Dissolve 2.0 g in 40 mL of water: the limit is 5 µg per g.
Zinc—
Dissolve 1 g in a mixture of 48 mL of water and 2 mL of sulfuric acid, and add, slowly and with constant agitation, 1 mL of potassium ferrocyanide solution (1 in 100): no turbidity is produced within 5 minutes.
Heavy metals, Method I 231—
Dissolve 6.0 g in 30 mL of water. Use 25 mL of this solution in the
Test Preparation, and use the remaining 5.0 mL in preparing the
Standard Preparation: the limit is 5 µg per g.
Organic volatile impurities, Method I 467:
meets the requirements.
Assay—
Transfer about 425 mg of Manganese Chloride, accurately weighed, to a 400-mL beaker, dissolve in about 25 mL of water, add 300 mg of ammonium chloride and 0.5 g of hydroxylamine hydrochloride, and swirl to dissolve. Warm slightly on a hot plate, and dilute with water to 100 mL. Add about 3 mL of triethanolamine, stir the solution, using, preferably, a magnetic stirrer, begin the titration by adding about 25 mL of 0.05 M edetate disodium VS, using a suitable buret, then add 10 mL of ammonia–ammonium chloride buffer TS, and 1 mL of
eriochrome black TS, and complete the titration with 0.05 M edetate disodium VS to a blue endpoint. Each mL of 0.05 M edetate disodium is equivalent to 6.292 mg of MnCl
2.
