Medium: water;900mL.

Apparatus 1: 100rpm.

Time: 30minutes.

Procedure— Determine the amount in solution by flame photometry,the test specimen being prepared by diluting the 900mLof the solution under test to 1000mLand a 20.0-mLfiltered aliquot being transferred to a 1000-mLvolumetric flask and treated with 500mLof water,1drop of hydrochloric acid,and 20mLof a suitable surfactant solution,appropriately diluted.Add water to volume,mix,and read on a suitable photometer together with the Standard preparationas directed in the Assayunder Lithium Carbonate Capsules.

Tolerances— Not less than 80%(Q)of the labeled amount of Li2CO3is dissolved in 30minutes.

Standard preparation— Prepare as directed in the Assayunder Lithium Carbonate Capsules.

Assay preparation— Weigh and finely powder not less than 20Tablets.Weigh accurately a portion of the powder,equivalent to about 600mg of lithium carbonate,and transfer to a 1000-mLvolumetric flask.Add 40mLof water and 5mLof hydrochloric acid,shake until the solid is well disintegrated,dilute with water to volume,and mix.Pipet 10mLof the resulting solution into a 1000-mLvolumetric flask,add about 800mLof water and 20mLof the surfactant solution,dilute with water to volume,and mix.

Procedure— Proceed as directed for Procedurein the Assayunder Lithium Carbonate Capsules.Calculate the quantity,in mg,of Li2CO3in the portion of Tablets taken by the formula: in which Cis the concentration,in µg per mL,of USP Lithium Carbonate RSin the Standard preparation,and Aand Sare the photometer readings of the Assay preparationand the Standard preparation,respectively.