A: Disperse 20 finely powdered Tablets in 25 mL of water, shake, and filter: a portion of the filtrate responds to the tests for Sodium 191.

B: Evaporate a 10-mL portion of the filtrate obtained in Identification test A to dryness. To the residue add a mixture of 0.1 mL of freshly prepared sodium alizarinsulfonate solution (1 in 1000) and 0.1 mL of a 1 in 1000 solution of zirconyl nitrate in 7 N hydrochloric acid: a yellow color is produced.

Buffer solution and Standard preparations— Prepare as directed in the Assay under Sodium Fluoride Oral Solution.

Assay preparation— Weigh and finely powder not less than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 10 mg of fluoride, to a plastic 500-mL conical flask containing 400 mL of water. Heat on a steam bath for 25 minutes with occasional shaking, cool to room temperature, transfer to a 500-mL volumetric flask, dilute with water to volume, and mix.

Procedure— Proceed as directed for Procedure in the Assay under Sodium Fluoride Oral Solution. Calculate the quantity, in mg, of fluoride ion in the portion of Tablets taken by the formula: in which C is the determined concentration, in µg per mL, of fluoride ion in the Assay preparation. Multiply the quantity of fluoride ion by 2.21 to obtain the quantity of NaF.