Medium: water;900mL.

Apparatus 1: 100rpm.

Time: 30minutes.

Procedure— Determine the amount of Li2CO3dissolved in filtered portions of the solution under test with a suitable flame photometer,as directed in the Assay.

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

Standard preparation— Transfer to a 100-mLvolumetric flask about 30mg of USP Lithium Carbonate RS,accurately weighed.Add about 20mLof water and 0.5mLof hydrochloric acid,shake until dissolved,dilute with water to volume,and mix.Pipet 20mLof the resulting solution into a 1000-mLvolumetric flask,add about 800mLof water and 20mLof a suitable surfactant solution,appropriately diluted,dilute with water to volume,and mix.

Assay preparation— Empty as completely as possible the contents of not less than 20Capsules.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 sample 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— Employ a suitable flame photometer,and adjust the instrument with the surfactant solution.Aspirate into the photometer the Standard preparationand the Assay preparation,and measure the emission at about 671nm.Calculate the quantity,in mg,of Li2CO3in the portion of Capsules 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.