Phosphoric Acid
H3PO4 98.00

Phosphoric acid.
Phosphoric acid [7664-38-2].
»Phosphoric Acid contains not less than 85.0percent and not more than 88.0percent,by weight,of H3PO4.
Caution—Avoid contact,as Phosphoric Acid rapidly destroys tissues.
Packaging and storage— Preserve in tight containers.
Identification— When carefully neutralized with 1Nsodium hydroxide,phenolphthalein TSbeing used as the indicator,it responds to the tests for Phosphate á191ñ.
Sulfate á221ñ— Dilute 6mLof Phosphoric Acid with 90mLof water,and add 1mLof barium chloride TS:no precipitate is formed immediately.
Alkali phosphates— Transfer 1mLof it to a graduated cylinder,and add 6mLof ether and 2mLof alcohol:no turbidity is produced.
Limit of nitrate— Dilute 6mLof Phosphoric Acid with 14mLof water,mix 5mLof the dilution with about 0.1mLof indigo carmine TS,then add 5mLof sulfuric acid:the blue color is not discharged within 1minute.
Phosphorous or hypophosphorous acid— Dilute 6mLof Phosphoric Acid with 14mLof water.Gently warm 5mLof the dilution,and add 2mLof silver nitrate TS:the mixture does not become brownish.
Assay— Weigh accurately about 1g of Phosphoric Acid in a tared,glass-stoppered flask,and dilute it with water to about 120mL.Add 0.5mLof thymolphthalein TS,and titrate with 1Nsodium hydroxide VSto the first appearance of a blue color.Perform a blank determination,and make any necessary correction.Each mLof 1Nsodium hydroxide is equivalent to 49.00mg of H3PO4.
Auxiliary Information— Staff Liaison:Karen A Russo,Ph.D.,Scientist
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 3050
Phone Number:1-301-816-8379