Diluted Phosphoric Acid
»Diluted Phosphoric Acid contains,in each 100mL,not less than 9.5g and not more than 10.5g of H3PO4.
Diluted Phosphoric Acid may be prepared as follows:
Phosphoric Acid 69mL
Purified Water,a sufficient quantity,
to make		 1000mL
Mix the ingredients.
Packaging and storage— Preserve in tight containers.
Heavy metals,Method Iá231ñ— Dilute 10g (9.5mL)with 10mLof water,add 6mLof 1Nsodium hydroxide,and dilute with water to 50mL.Dilute 20mLof this solution with water to 25mL:the limit is 5ppm.
Alkali phosphates— Evaporate 20mLon a steam bath to a weight of about 5g.Cool,transfer 2mLto a graduated cylinder,and add 6mLof ether and 2mLof alcohol:no turbidity is produced.
Other tests— Without further dilution,100mLof Diluted Phosphoric Acid responds to the Identificationtest and meets the requirements of the tests for Nitrate,Phosphorous or hypophosphorous acid,and Sulfateunder Phosphoric Acid.
Assay— Transfer 10.0mLof Diluted Phosphoric Acid to a flask,and dilute it with water to about 50mL.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:Daniel K.Bempong,Ph.D.,Scientist
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 3050
Phone Number:1-301-816-8143
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