Zinc Chloride
(zink klor' ide).

ZnCl2 136.30
Zinc chloride     [7646-85-7].
Zinc Chloride contains NLT 97.0% and NMT 100.5% of ZnCl2.
•  A. Identification Tests—General, Zinc 191: Meets the requirements
•  B. Identification Tests—General, Chloride 191: Meets the requirements
•  Procedure
Sample solution:  Dissolve 12 g of Zinc Chloride in 500 mL of water in a 1-L volumetric flask. Add 12 g of ammonium chloride, and dilute with water to volume.
Analysis:  Pipet 25 mL of the Sample solution into a 400-mL beaker. Add 100 mL of water, 10 mL of ammonia–ammonium chloride buffer TS, and 1 mL of 0.5 mg/mL of eriochrome black T solution. 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.
Acceptance criteria:  97.0%–100.5%
•  Chloride and Sulfate, Sulfate 221
Sample solution:  1.0 g in 30 mL of water
Acceptance criteria:  20 mL of the Sample solution shows no more sulfate than corresponds to 0.20 mL of 0.020 N sulfuric acid (0.03%).
•  Lead 251
Standard solution:  Add 5 mL of water, 2.50 mL of Standard lead solution (see Heavy Metals 231), and 15 mL of Potassium cyanide solution (100 mg/mL) to a similar color-comparison tube.
Sample solution:  Dissolve 0.50 g in 5 mL of water, and transfer the solution to a color-comparison tube. Add 15 mL of Potassium cyanide solution (100 mg/mL), and allow the mixture to become clear.
Analysis:  To each tube add 0.1 mL of sodium sulfide TS. Mix the contents of each tube, and allow to stand for 5 min.
Acceptance criteria:  Viewed downward over a white surface, the Sample solution is not darker than the Standard solution (NMT 0.005%).
•  Limit of Ammonium Salts
Sample solution:  100 mg/mL
Analysis:  To 5 mL of Sample solution add 1 N sodium hydroxide until the precipitate first formed is redissolved, then warm the solution.
Acceptance criteria:  No odor of ammonia is perceptible.
•  Limit of Oxychloride
Sample solution:  Dissolve 1.0 g in 20 mL of water, and add 20 mL of alcohol.
Analysis:  To 10 mL of the Sample solution add 0.30 mL of 1.0 N hydrochloric acid.
Acceptance criteria:  The solution becomes perfectly clear.
•  Alkalies and Alkaline Earths
Sample solution:  Dissolve 2.0 g in 150 mL of water contained in a 200-mL volumetric flask. Add sufficient ammonium sulfide TS to precipitate the zinc completely, and dilute with water to volume. Filter through a dry filter, and reject the first portion of the filtrate.
Analysis:  To 100 mL of the Sample solution add 5 drops of sulfuric acid. Evaporate to dryness, and ignite.
Acceptance criteria:  The weight of the residue is NMT 10 mg (1.0%).
•  Packaging and Storage: Preserve in tight containers.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Feiwen Mao, M.S.
Senior Scientific Liaison
(SM32010) Monographs - Small Molecules 3
USP35–NF30 Page 5069