Sodium Fluoride
NaF 41.99

Sodium fluoride.
Sodium fluoride [7681-49-4].
» Sodium Fluoride contains not less than 98.0 percent and not more than 102.0 percent of NaF, calculated on the dried basis.
Packaging and storage— Preserve in well-closed containers.
A: Place 1 g in a platinum crucible in a well-ventilated hood, add 15 mL of sulfuric acid, and cover the crucible with a piece of clear, polished glass. Heat the crucible on a steam bath for 1 hour, remove the glass cover, rinse it in water, and wipe dry: the surface of the glass is etched.
B: A solution (1 in 25) responds to the tests for Sodium 191.
Acidity or alkalinity— Dissolve 2.0 g in 40 mL of water in a platinum dish, add 10 mL of a saturated solution of potassium nitrate, cool the solution to 0, and add 3 drops of phenolphthalein TS. If no color appears, a pink color persisting for 15 seconds is produced by not more than 2.0 mL of 0.10 N sodium hydroxide. If the solution is colored pink by the addition of phenolphthalein TS, it is rendered colorless by not more than 0.50 mL of 0.10 N sulfuric acid. Save the neutralized solution for the test for Fluosilicate.
Loss on drying 731 Dry it at 150 for 4 hours: it loses not more than 1.0% of its weight.
Fluosilicate— After the solution from the test for Acidity or alkalinity has been neutralized, heat to boiling, and titrate while hot with 0.10 N sodium hydroxide until a permanent pink color is obtained: not more than 1.5 mL of 0.10 N sodium hydroxide is required.
Chloride— Dissolve 300 mg in 20 mL of water, and add 200 mg of boric acid, 1 mL of nitric acid, and 1 mL of 0.1 N silver nitrate: any turbidity produced is not greater than that of a blank to which has been added 1.0 mL of 0.0010 N hydrochloric acid (0.012%).
Heavy metals 231 To 1 g, in a platinum dish or crucible, under a hood, add 1 mL of water and 3 mL of sulfuric acid, and heat at as low a temperature as practicable until all of the sulfuric acid has been expelled. Dissolve the residue in 20 mL of water, neutralize the solution to phenolphthalein TS with ammonium hydroxide, add 1 mL of glacial acetic acid, dilute with water to 45 mL, filter, and use 30 mL of the filtrate for the test: the limit is 0.003%.
Assay— To 80.0 mg of Sodium Fluoride add a mixture of 5 mL of acetic anhydride and 20 mL of glacial acetic acid, and heat to dissolve. Allow to cool, and add 20 mL of dioxane. Add 1 drop of crystal violet TS, and titrate with 0.1 N perchloric acid VS to a green endpoint. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N perchloric acid is equivalent to 4.199 mg of NaF.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Elena Gonikberg, Ph.D.
Senior Scientist
(MDGRE05) Monograph Development-Gastrointestinal Renal and Endocrine
USP32–NF27 Page 3574
Pharmacopeial Forum: Volume No. 34(3) Page 653
Chromatographic Column—
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.