Hypophosphorous Acid
H3PO2 66.00

Phosphinic acid.
Hypophosphorous acid [6303-21-5].
»Hypophosphorous Acid contains not less than 30.0percent and not more than 32.0percent of H3PO2.
Packaging and storage— Preserve in tight containers.
Identification— It responds to the tests for Hypophosphite á191ñ.
Limit of barium and oxalate—
Test solution— Dilute Hypophosphorous Acid with 3volumes of water,and use this solution for the following tests.
Barium— Neutralize 30mLof Test solutionwith 6Nammonium hydroxide:the mixture exhibits little or no precipitation.Filter,acidify 10mLof the filtrate with hydrochloric acid,and add 2mLof potassium sulfate TS:no turbidity is produced.
Oxalate— Another 10-mLportion of the filtrate obtained in the test for Bariumshows no turbidity upon the addition of 1mLof calcium chloride TS.
Heavy metals,Method Iá231ñ— Place 0.90mL(1g)in a small beaker,and add 3mLof water.Add 1mLof nitric acid,and evaporate on a steam bath to about 1mL.Again add 1mLof nitric acid,and evaporate on a steam bath.Dissolve the residue in 3mLof water,add 6Nammonium hydroxide until the solution is distinctly alkaline to litmus,then boil gently until the odor of ammonia disappears.Add 2mLof 1Nacetic acid and 15mLof warm water,filter,and dilute the filtrate with water to 25mL:the limit is 0.002%.
Assay— Pour about 7mLof Hypophosphorous Acid into a tared,glass-stoppered flask,and weigh accurately.Dilute with about 25mLof water,add phenolphthalein TS,and titrate with 1Nsodium hydroxide VS.Each mLof 1Nsodium hydroxide is equivalent to 66.00mg of H3PO2.
Auxiliary Information— Staff Liaison:Catherine Sheehan,B.Sc.,Scientist
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 3020
Phone Number:1-301-816-8262