Boric Acid
H3BO3 61.83

Boric acid (H3BO3).
Boric acid (H3BO3) [10043-35-3].
» Boric Acid contains not less than 99.5 percent and not more than 100.5 percent of H3BO3, calculated on the dried basis.
Packaging and storage— Preserve in well-closed containers.
Labeling— Label the container with a warning that it is not for internal use.
Solubility in alcohol— One g dissolves completely in 10 mL of boiling alcohol.
Completeness of solution— One g dissolves in 25 mL of water, producing a clear solution.
Identification— It responds to the tests for Borate 191.
Loss on drying 731 Dry it over silica gel for 5 hours: it loses not more than 0.5% of its weight.
Heavy metals, Method I 231 Dissolve 1 g in 23 mL of water, and add 2 mL of 1 N acetic acid: the limit is 0.002%.
Assay— Dissolve about 2 g of Boric Acid, accurately weighed, in 100 mL of a mixture of equal volumes of glycerin and water, previously neutralized to phenolphthalein TS, and titrate with 1 N sodium hydroxide VS. Discharge the pink color by the addition of 50 mL of glycerin, neutralized to phenolphthalein TS, and continue the titration until the pink color reappears. Each mL of 1 N sodium hydroxide is equivalent to 61.83 mg of H3BO3.
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Topic/Question Contact Expert Committee
Monograph Robert H. Lafaver, B.A.
(EM105) Excipient Monographs 1
USP32–NF27 Page 1177