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Calcium Sulfate
CaSO4 136.14
Sulfuric acid,calcium salt (1:1).
Calcium sulfate (1:1) 136.14 [7778-18-9].
Dihydrate 172.17 [10101-41-4].
?Calcium Sulfate is anhydrous or contains two molecules of water of hydration.It contains not less than 98.0percent and not more than 101.0percent of CaSO4,calculated on the dried basis.
Packaging and storage— Preserve in well-closed containers.
Labeling— Label it to indicate whether it is anhydrous or the dihydrate.
Identification— Dissolve about 200mg by warming in a mixture of 4mLof 3Nhydrochloric acid and 16mLof water.This solution responds to the tests forCalcium á191?and forSulfate á191?.
Loss on drying á731?— Dry it at a temperature not lower than 250 to constant weight:the anhydrous form loses not more than 1.5%of its weight,and the dihydrate loses between 19.0%and 23.0%of its weight.
Iron á241?— Dissolve 100mg in 8mLof 3Nhydrochloric acid,and dilute with water to 47mL:the limit is 0.01%.
Heavy metals,Method Iá231?— Mix2.0gwith 20mLof water,add 25mLof 3Nhydrochloric acid,and heat to boiling to dissolve the test specimen.Cool,and add ammonium hydroxide to a pHof 7.Filter,evaporate to a volume of about 25mL,and refilter,if necessary,to obtain a clear solution:the limit is 0.001%.
Assay— Dissolve about 300mg of Calcium Sulfate,accurately weighed,in 100mLof water and 4mLof 3Nhydrochloric acid.Boil,if necessary,to dissolve,and cool before titrating.While stirring,preferably with a magnetic stirrer,add,in the order named,0.5mLof triethanolamine,300mg of hydroxy naphthol blue,and,from a 50-mLburet,about 30mLof 0.05Medetate disodium VS.Add sodium hydroxide solution (45in100)until the initial red color changes to clear blue.Continue to add it dropwise until the color changes to violet,and add an additional 0.5mL.The pHis between 12.3and 12.5.Continue the titration dropwise with 0.05Medetate disodium VSto the appearance of a clear-blue endpoint that persists for not less than 60seconds.Each mLof 0.05Medetate disodium is equivalent to 6.807mg of CaSO4.
Auxiliary Information— Staff Liaison:Catherine Sheehan,B.Sc.,Scientist
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 2971
Pharmacopeial Forum:Volume No.27(6)Page 3337
Phone Number:1-301-816-8262
