A: Infrared Absorption á197Sñ—

B: The addition of 1Nhydrochloric acid to a Tablet produces effervescence,and the resulting solution,after having been filtered,responds to the tests for Calcium á191ñ.

C: Heat 2Tablets in 20mLof 1Nsulfuric acid.Cool,add 20mLof alcohol,mix,and allow to stand for 30minutes.Filter this solution,and to the filtrate add 2mLof 1Nhydrochloric acid:this solution responds to the tests for Magnesium á191ñ.

Foaming solution— Dissolve 500µg of FD&C Blue No.1and 1g of octoxynol 9in 100mLof 0.1Nhydrochloric acid.

Procedure— [NOTE—For each test,use a clean,unused,250-mLcylindrical glass jar.]Transfer a quantity of finely powdered Tablets,which has completely passed though an 80-mesh sieve,equivalent to 20mg of simethicone,to a clean 250-mLcylindrical glass jar,fitted with a 50-mm cap,containing 100mLof Foaming solutionthat has been warmed to 37.Proceed as directed for Procedurein the test for Defoaming activityunder Simethicone,beginning with “Cap the jar.”The defoaming activity time does not exceed 45seconds.

Lanthanum chloride solution— Prepare as directed in the Assay for calcium carbonate and magnesium hydroxide.

Dilute hydrochloric acid— Prepare as directed in the Assay for polydimethylsiloxane.

Standard solution— Transfer 2.542g of sodium chloride,previously dried at 105for 2hours,to a 1000-mLvolumetric flask,dissolve in water,dilute with water to volume,and mix.Transfer 5.0mLof this solution to a 100-mLvolumetric flask,dilute with water to volume,and mix.Transfer 4.0mLof this solution to a second 100-mLvolumetric flask containing 6.0mLof Dilute hydrochloric acidand 2.0mLof Lanthanum chloride solution,dilute with water to volume,and mix.This solution contains 2.0µg of sodium (Na)per mL.

Test preparation— Transfer 3.0mLof the aqueous layer retained from the preparation of the Assay preparationin the Assay for polydimethylsiloxaneto a 50-mLvolumetric flask containing 1.0mLof Lanthanum chloride solution,dilute with water to volume,and mix.

Blank solution— Transfer 15.0mLof Dilute hydrochloric acidand 5.0mLof Lanthanum chloride solutionto a 250-mLvolumetric flask,dilute with water to volume,and mix.

Procedure— Concomitantly determine the absorbances of the Standard solutionand the Test preparationat the sodium emission line at 589.0nm with a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering á851ñ)equipped with a sodium hollow-cathode lamp and an air–acetylene flame,using the Blank solutionas the blank.Calculate the mg of sodium (Na)in each Tablet taken by the formula: in which Cis the concentration,in µg per mL,of sodium in the Standard preparation;Ais the average weight,in mg,of each Tablet;Wis the weight,in mg,of the portion of Tablets taken to prepare the Assay preparationin the Assay for polydimethylsiloxane;and AUand ASare the absorbances of the Assay preparationand the Standard preparation,respectively.Each Tablet contains not more than the number of mg of sodium stated on the label.

Saccharin solution— Prepare a solution of saccharin in 4-methyl-2-pentanone containing 12.5mg per mL.

Dilute hydrochloric acid— Mix 200mLof hydrochloric acid with sufficient water to make 1000mL.

Standard preparation— Dissolve a suitable quantity of USP Polydimethylsiloxane RSin 4-methyl-2-pentanone to obtain a stock solution having a known concentration of about 1mg per mL.On the day of use,transfer 20.0mLof this solution and 5.0mLof Saccharin solutionto a 250-mLvolumetric flask,dilute with 4-methyl-2-pentanone to volume,and mix.This solution contains about 0.08mg of USP Polydimethylsiloxane RSper mL.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 20mg of polydimethylsiloxane,to a 125-mLseparator.Cautiously add 50.0mLof Dilute hydrochloric acid,and swirl until the reaction subsides.Insert the stopper,and mix.Carefully release the pressure,add 50.0mLof 4-methyl-2-pentanone,and mix for 10minutes.Allow the layers to separate,and drain the aqueous layer into a suitable stoppered container.[NOTE—Retain this aqueous layer for use in preparing the Assay preparation in the Assay for calcium carbonate and magnesium hydroxide and for the preparation of the Test preparation in the test for Sodium content.]Pass the organic layer through a filter containing 50g of anhydrous sodium sulfate.Transfer 10.0mLof the filtrate to a 50-mLvolumetric flask,add 1.0mLof Saccharin solution,dilute with methyl isobutyl ketone to volume,and mix.

Blank solution— Transfer 1.0mLof Saccharin solutionto a 50-mLvolumetric flask,dilute with 4-methyl-2-pentanone to volume,and mix.

Procedure— Concomitantly determine the absorbances of the Standard preparationand the Assay preparationat the silicon emission line at 251.6nm,with a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering á851ñ)equipped with a silicon hollow-cathode lamp and a nitrous oxide–acetylene flame,using the Blank solutionas the blank.Calculate the quantity,in mg,of polydimethylsiloxane in each Tablet taken by the formula: in which Cis the concentration,in mg per mL,of USP Polydimethylsiloxane RSin the Standard preparation;Ais the average weight,in mg,of each Tablet;Wis the weight,in mg,of the portion of Tablets taken to prepare the Assay preparation;and AUand ASare the absorbances of the Assay preparationand the Standard preparation,respectively.

Lanthanum chloride solution— Transfer 26.8g of lanthanum chloride to a 200-mLvolumetric flask,add 100mLof water,and carefully add 50mLof hydrochloric acid.Mix,and allow to cool.Dilute with water to volume,and mix.

Dilute hydrochloric acid— Prepare as directed in the Assay for polydimethylsiloxane.

Calcium stock standard solution— Transfer 499.5mg of primary standard calcium carbonate to a 200-mLvolumetric flask,and add 10mLof water.Carefully add 5mLof Dilute hydrochloric acid,and swirl to dissolve the calcium carbonate.Dilute with water to volume,and mix.This solution contains 1000µg of calcium (Ca)per mL.

Magnesium stock standard solution— Transfer 1.000g of magnesium metal to a 1000-mLvolumetric flask containing 10mLof water,slowly add 10mLof hydrochloric acid,and swirl to dissolve the metal.Dilute with water to volume,and mix.This solution contains 1000µg of magnesium (Mg)per mL.

Calciumand magnesium standard preparation— To a 250-mLvolumetric flask add 10.0mLof Calcium stock standard solutionand 5.0mLof Magnesium stock standard solution,dilute with water to volume,and mix.This solution contains 40µg of calcium (Ca)and 20µg of magnesium (Mg)per mL.On the day of use,transfer 4.0mLof this solution to a 100-mLvolumetric flask containing 2.0mLof Lanthanum chloride solution,dilute with water to volume,and mix.This solution contains 1.6µg of calcium (Ca)and 0.8µg of magnesium (Mg)per mL.

Assay preparation— Transfer an accurately measured volume of the aqueous layer retained from the preparation of the Assay preparationin the Assay for polydimethylsiloxane,equivalent to about 28mg of calcium carbonate,to a 200-mLvolumetric flask,dilute with water to volume,and mix.Transfer 3.0mLof this solution to a 100-mLvolumetric flask containing 2.0mLof Lanthanum chloride solution,dilute with water to volume,and mix.

Blank solution— Transfer 5.0mLof Lanthanum chloride solutionto a 250-mLvolumetric flask,dilute with water to volume,and mix.

Procedure for calcium carbonate— Concomitantly determine the absorbances of the Standard preparationand the Assay preparationat the calcium emission line at 422.7nm,with a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering á851ñ)equipped with a calcium hollow-cathode lamp and an nitrous oxide–acetylene flame,using the Blank solutionas the blank.Calculate the quantity,in mg,of calcium carbonate (CaCO3)in each Tablet taken by the formula: in which 100.09is the molecular weight of calcium carbonate,40.08is the atomic weight of calcium,Cis the concentration,in µg per mL,of calcium in the Standard preparation,Vis the volume,in mL,of the aqueous layer retained from the preparation of the Assay preparationin the Assay for polydimethylsiloxaneused to prepare the Assay preparation,Ais the average weight,in mg,of each Tablet,Wis the weight,in mg,of the portion of Tablets taken to prepare the Assay preparationin the Assay for polydimethylsiloxane,and AUand ASare the absorbances of the Assay preparationand the Standard preparation,respectively.

Procedure for magnesium hydroxide— Concomitantly determine the absorbances of the Standard preparationand the Assay preparationat the magnesium emission line at 285.2nm,with a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering á851ñ)equipped with a magnesium hollow-cathode lamp and a nitrous oxide–acetylene flame,using the Blank solutionas the blank.Calculate the quantity,in mg,of magnesium hydroxide [Mg(OH)2]in each Tablet taken by the formula: in which 58.34is the molecular weight of magnesium hydroxide,24.305is the atomic weight of magnesium;Cis the concentration,in µg per mL,of magnesium in the Standard preparation;Vis the volume,in mL,of the aqueous layer retained from the preparation of the Assay preparationin the Assay for polydimethylsiloxaneused to prepare the Assay preparation;Ais the average weight,in mg,of each Tablet taken;Wis the weight,in mg,of the portion of Tablets taken to prepare the Assay preparationin the Assay for polydimethylsiloxane;and AUand ASare the absorbances of the Assay preparationand the Standard preparation,respectively.