A: Disperse 20finely powdered Tablets in 25mLof water,shake,and filter:a portion of the filtrate responds to the tests for Sodium á191ñ.

B: Evaporate a 10-mLportion of the filtrate obtained in Identificationtest Ato dryness.To the residue add a mixture of 0.1mLof freshly prepared sodium alizarinsulfonate solution (1in 1000)and 0.1mLof a 1in 1000solution of zirconyl nitrate in 7Nhydrochloric acid:a yellow color is produced.

Buffer solution andStandard preparations— Prepare as directed in the Assayunder Sodium Fluoride Oral Solution.

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

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