Packaging and storage
Preserve in tight containers.
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.
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.
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.
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 ammoniaammonium 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.