Sodium Fluoride
NaF 41.99

Sodium fluoride.
Sodium fluoride [7681-49-4].
»Sodium Fluoride contains not less than 98.0percent and not more than 102.0percent of NaF,calculated on the dried basis.
Packaging and storage— Preserve in well-closed containers.
Identification—
A: Place 1g in a platinum crucible in a well-ventilated hood,add 15mLof sulfuric acid,and cover the crucible with a piece of clear,polished glass.Heat the crucible on a steam bath for 1hour,remove the glass cover,rinse it in water,and wipe dry:the surface of the glass is etched.
B: Asolution (1in 25)responds to the tests for Sodium á191ñ.
Acidity or alkalinity— Dissolve 2.0g in 40mLof water in a platinum dish,add 10mLof a saturated solution of potassium nitrate,cool the solution to 0,and add 3drops of phenolphthalein TS.If no color appears,a pink color persisting for 15seconds is produced by not more than 2.0mLof 0.10Nsodium hydroxide.If the solution is colored pink by the addition of phenolphthalein TS,it is rendered colorless by not more than 0.50mLof 0.10Nsulfuric acid.Save the neutralized solution for the test for Fluosilicate.
Loss on drying á731ñ— Dry it at 150for 4hours:it loses not more than 1.0%of its weight.
Fluosilicate— After the solution from the test for Acidity or alkalinityhas been neutralized,heat to boiling,and titrate while hot with 0.10Nsodium hydroxide until a permanent pink color is obtained:not more than 1.5mLof 0.10Nsodium hydroxide is required.
Chloride— Dissolve 300mg in 20mLof water,and add 200mg of boric acid,1mLof nitric acid,and 1mLof 0.1Nsilver nitrate:any turbidity produced is not greater than that of a blank to which has been added 1.0mLof 0.0010Nhydrochloric acid (0.012%).
Heavy metals á231ñ— To 1g,in a platinum dish or crucible,under a hood,add 1mLof water and 3mLof sulfuric acid,and heat at as low a temperature as practicable until all of the sulfuric acid has been expelled.Dissolve the residue in 20mLof water,neutralize the solution to phenolphthalein TSwith ammonium hydroxide,add 1mLof glacial acetic acid,dilute with water to 45mL,filter,and use 30mLof the filtrate for the test:the limit is 0.003%.
Organic volatile impurities,Method Iá467ñ: meets the requirements.
Assay— [NOTE—Store all solutions,except the Buffer solution,in plastic containers.]
Buffer solution andStandard preparations— Prepare as directed in the Assayunder Sodium Fluoride Oral Solution.
Assay preparation— Transfer about 100mg of Sodium Fluoride,accurately weighed,to a 250-mLvolumetric flask.Add 50mLof water,mix for 5minutes,dilute with water to volume,and mix.Transfer 10.0mLof this solution to a 50-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 NaFin the portion of Sodium Fluoride taken by the formula:
(41.99/18.998)(1.25C),
in which 41.99is the molecular weight of sodium fluoride;18.998is the atomic weight of fluorine;and Cis the determined concentration of fluoride,in µg per mL,in the Assay preparation.
Auxiliary Information— Staff Liaison:Elena Gonikberg,Ph.D.,Scientist
Expert Committee:(PA4)Pharmaceutical Analysis 4
USP28–NF23Page 1783
Phone Number:1-301-816-8251