Packaging and storage—
Preserve in tight containers.
Identification—
A solution of it responds to the tests for
Zinc 
191
and for
Chloride 191.
Limit of oxychloride—
Dissolve 1.0 g in 20 mL of water, add 20 mL of alcohol, and mix. To 10 mL of the mixture add 0.30 mL of 1.0 N hydrochloric acid: the solution becomes perfectly clear.
Sulfate 221—
Dissolve 1.0 g in 30 mL of water: 20 mL of this solution shows no more sulfate than corresponds to 0.20 mL of 0.020 N sulfuric acid (0.03%).
Limit of ammonium salts—
To 5 mL of a solution (1 in 10) add 1 N sodium hydroxide until the precipitate first formed is redissolved, and then warm the solution: no odor of ammonia is perceptible.
Lead 251—
Dissolve 0.50 g in 5 mL of water, and transfer the solution to a color-comparison tube (
A). Add 15 mL of
Potassium Cyanide Solution (1 in 10), mix, and allow the mixture to become clear. In a similar, matched color-comparison tube (
B) place 5 mL of water, and add 2.50 mL of
Standard Lead Solution (see
Heavy Metals 231) and 15 mL of
Potassium Cyanide Solution (1 in 10). Add to the solution in each tube 0.1 mL of
sodium sulfide TS. Mix the contents of each tube, and allow to stand for 5 minutes: viewed downward over a white surface, the solution in tube
A is not darker than that in tube
B (indicating not more than 0.005% of lead).
Alkalies and alkaline earths—
Dissolve 2.0 g in about 150 mL of water contained in a 200-mL volumetric flask. Add sufficient ammonium sulfide TS to precipitate the zinc completely, dilute with water to volume, and mix. Filter through a dry filter, and reject the first portion of the filtrate. To 100 mL of the subsequent filtrate add 5 drops of sulfuric acid, evaporate to dryness, and ignite: the weight of the residue does not exceed 10 mg (1.0%).
Organic volatile impurities, Method I 467:
meets the requirements.
Assay—
Dissolve about 12 g of Zinc Chloride, accurately weighed, in about 500 mL of water in a 1 L volumetric flask, add 12 g of ammonium chloride, dilute with water to volume, and mix. Pipet 25 mL of the solution into a 400-mL beaker, add 100 mL of water, 10 mL of ammonia–ammonium chloride buffer TS, and 1 mL of eriochrome black T solution (1 in 2000), and titrate with 0.05 M edetate disodium VS to a deep blue endpoint. Each mL of 0.05 M edetate disodium is equivalent to 6.815 mg of ZnCl2.
