ZnCl2 136.30

Zinc chloride.
Zinc chloride [7646-85-7].

Packaging and storage— Preserve in tight containers.

Identification— Asolution of it responds to the tests for Zinc á191ñand for Chloride á191ñ.

Limit of oxychloride— Dissolve 1.0g in 20mLof water,add 20mLof alcohol,and mix.To 10mLof the mixture add 0.30mLof 1.0Nhydrochloric acid:the solution becomes perfectly clear.

Sulfate á221ñ— Dissolve 1.0g in 30mLof water:20mLof this solution shows no more sulfate than corresponds to 0.20mLof 0.020Nsulfuric acid (0.03%).

Limit of ammonium salts— To 5mLof a solution (1in 10)add 1Nsodium hydroxide until the precipitate first formed is redissolved,and then warm the solution:no odor of ammonia is perceptible.

Lead á251ñ— Dissolve 0.50g in 5mLof water,and transfer the solution to a color-comparison tube (A).Add 15mLof Potassium Cyanide Solution(1in 10),mix,and allow the mixture to become clear.In a similar,matched color-comparison tube (B)place 5mLof water,and add 2.50mLof Standard Lead Solution(see Heavy Metals á231ñ)and 15mLof Potassium Cyanide Solution(1in 10).Add to the solution in each tube 0.1mLof sodium sulfide TS.Mix the contents of each tube,and allow to stand for 5minutes:viewed downward over a white surface,the solution in tube Ais not darker than that in tube B(indicating not more than 0.005%of lead).

Alkalies and alkaline earths— Dissolve 2.0g in about 150mLof water contained in a 200-mLvolumetric flask.Add sufficient ammonium sulfide TSto 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 100mLof the subsequent filtrate add 5drops of sulfuric acid,evaporate to dryness,and ignite:the weight of the residue does not exceed 10mg (1.0%).

Organic volatile impurities,Method Iá467ñ: meets the requirements.

Assay— Dissolve about 12g of Zinc Chloride,accurately weighed,in about 500mLof water in a 1Lvolumetric flask,add 12g of ammonium chloride,dilute with water to volume,and mix.Pipet 25mLof the solution into a 400-mLbeaker,add 100mLof water,10mLof ammonia–ammonium chloride buffer TS,and 1mLof eriochrome black Tsolution (1in 2000),and titrate with 0.05Medetate disodium VSto a deep blue endpoint.Each mLof 0.05Medetate disodium is equivalent to 6.815mg of ZnCl2.

Expert Committee:(PA6)Pharmaceutical Analysis 6

USP28–NF23Page 2053

Phone Number:1-301-816-8389