CrCl3·6H2O 266.45

Chromium chloride (CrCl3)hexahydrate.
Chromium(3+)chloride hexahydrate [10060-12-5].

Anhydrous 158.36 [10025-73-7].

Packaging and storage— Preserve in tight containers.

Identification—

Insoluble matter— Transfer 10g to a 250-mLbeaker,add 100mLof water,cover the beaker,and heat to boiling.Digest the hot solution on a steam bath for 30minutes,and filter through a tared filtering crucible of fine porosity.Rinse the beaker with hot water,passing the rinsings through the filter,and wash the filter with hot water until the last washing is colorless.Dry the filter at 105:the weight of the residue does not exceed 1mg (0.01%).

Substances not precipitated by ammonium hydroxide— Dissolve 2.0g in 80mLof water,heat the solution to boiling,and add a slight excess of ammonium hydroxide.Continue heating to remove the excess ammonia,cool,dilute with water to 100.0mL,and mix.Pass through a retentive filter,and transfer 50.0mLof the clear filtrate to an evaporating dish that previously has been ignited and tared.Add 0.5mLof sulfuric acid to the filtrate,evaporate on a steam bath to dryness,heat gently to remove the excess acid,and ignite gently:the weight of the residue does not exceed 2.0mg (0.20%as sulfate).

Sulfate á221ñ— Prepare a test solution by dissolving 2.0g in 10mLof water.Add 1mLof 3Nhydrochloric acid,filter if necessary to obtain a clear solution,wash the filter with two 5-mLportions of water,and dilute with water to 40mL.Prepare a control solution in a similar manner,but use 1.0g of the substance under test,and after the filtration step add 0.10mLof 0.020Nsulfuric acid.To each solution add 3mLof barium chloride TS,mix,and allow to stand overnight.Decant most of the supernatants,without disturbing the precipitates,but leaving twice the volume of liquid in the control solution as in the test solution.Dilute each solution with water to 25mL,and sonicate for 1minute:any turbidity in the test solution does not exceed that in the control solution (0.01%).

Iron á241ñ— Dissolve 1.0g in 100mLof water,and mix.Transfer 10mLof this solution to a 100-mLcolor comparison tube,dilute with water to 45mL,add 2mLof hydrochloric acid,and mix (Test Preparation).Proceed as directed for Procedure,except to add 15mLof butyl alcohol to the Test Preparationand the Standard Preparationat the same time that the Ammonium Thiocyanate Solutionis added.Shake for 30seconds,and allow the layers to separate:the color in the upper butyl alcohol layer from the Test Preparationis not darker than that from the Standard Preparation.The limit is 0.01%.

Assay— Dissolve about 0.4g of Chromic Chloride,accurately weighed,in 100mLof water contained in a glass-stoppered,500-mLconical flask,add 5mLof 5Nsodium hydroxide,and mix.Pipet,slowly,4mLof 30percent hydrogen peroxide into the flask,and boil the solution for 5minutes.Cool the solution slightly,and add 5mLof nickel sulfate solution (1in 20).Boil the solution until no more oxygen is evolved,cool,and add 2Nsulfuric acid dropwise until the color of the solution changes from yellow to orange.Add to the flask a freshly prepared solution of 4g of potassium iodide and 2g of sodium bicarbonate in 100mLof water,then add 6mLof hydrochloric acid.Immediately insert the stopper in the flask,and allow to stand in the dark for 10minutes.Rinse the stopper and the sides of the flask with a few mLof water,and titrate the liberated iodine with 0.1Nsodium thiosulfate VSto an orange color.Add 3mLof starch TS,and continue the titration to a blue-green endpoint.Each mLof 0.1Nsodium thiosulfate is equivalent to 8.882mg of CrCl3·6H2O.

Expert Committee:(PA1)Pharmaceutical Analysis 1

USP28–NF23Page 465

Phone Number:1-301-816-8379