A: Cut a Tablet into pieces,add 50mLof 1Nsulfuric acid,stir until the pieces disintegrate,and heat on a steam bath for 10minutes.Cool,add 50mLof alcohol,and stir.The mixture so obtained responds toIdentificationtestsA,B,andCunderAlumina,Magnesia,and Calcium Carbonate Oral Suspension,beginning underIdentification testAwith “place in an ice bath for 30minutes.”

B: Infrared Absorption á197Sñ—

0.55(0.0385A)+0.8(0.0343M)+0.9(0.02C),

Foaming solution— Dissolve 1g of octoxynol 9in 100mLof 0.3Nhydrochloric acid.

Procedure— [NOTE—For each test,use a clean 250-mLcylindrical glass jar.]Weigh not fewer than 10Tablets,cut them into small pieces,and mix.Transfer a portion of mixed Tablet pieces,equivalent to about 20mg of simethicone,to a clean 250-mLcylindrical glass jar,fitted with a 50-mm cap,containing 100mLofFoaming solutionthat has been warmed to 37.After effervescence ceases,proceed as directed forProcedurein theDefoaming activitytest underSimethicone,beginning with “Cap the jar.”The defoaming activity time does not exceed 45seconds.

Potassium chloride solution— Dissolve 3g of potassium chloride in water in a 100-mLvolumetric flask,dilute with water to volume,and mix.

Dilute hydrochloric acid— Prepare by mixing 226mLof hydrochloric acid with sufficient water to make 1000mL.

Standard solution— Transfer 2.5420g of sodium chloride,previously dried at 105for 2hours,to a 1000-mLvolumetric flask,dissolve in and dilute with water to volume,and mix.Transfer 10.0mLof this solution to a 100-mLvolumetric flask,dilute with water to volume,and mix.Transfer 10.0mLof this solution to a second 100-mLvolumetric flask,dilute with water to volume,and mix.To three separate 100-mLvolumetric flasks,each containing 10.0mLofPotassium chloride solutionand 3.0mLofDilute hydrochloric acid,add,respectively,10.0,20.0,and 30.0mLof this solution.These solutions contain 1.0,2.0,and 3.0µg of sodium (Na)per mL,respectively.

Test solution— Accurately weigh 10Tablets,and determine the average weight,A,in mg.Cut 4Tablets into pieces,combine the pieces,and weigh them.Transfer the combined pieces to a 500-mLvolumetric flask,add 150mLofDilute hydrochloric acid,and swirl gently to disintegrate the pieces.Dilute with water to volume,and mix.Transfer 10.0mLof this solution to a 100-mLvolumetric flask,add 10.0mLofPotassium chloride solution,dilute with water to volume,and mix.

Blank solution— Transfer 3.0mLofDilute hydrochloric acidand 10.0mLofPotassium chloride solutionto a 100-mLvolumetric flask,dilute with water to volume,and mix.

Procedure— Concomitantly determine the absorbances of theStandard solutions and theTest solutionat the sodium emission line at 589.0nm with a suitable atomic absorption spectrophotometer (seeSpectrophotometry and Light-Scattering á851ñ)equipped with a sodium hollow-cathode lamp and an air–acetylene flame,using theBlank solutionas the blank.Plot the absorbances of theStandard solutions versus concentration,in µg per mL,of sodium,and draw the straight line best fitting the three plotted points.From the graph so obtained,determine the concentration,C,in µg per mL,of sodium in theTest solution.Calculate the mg of sodium (Na)in each Tablet taken by the formula: in which Ais the average weight,in mg,of each Tablet and Wis the weight,in mg,of the portion of Tablets taken to prepare theTest solution.Tablets contain not more than 5mg of sodium per Tablet,except when labeled as containing more than 5mg of sodium per Tablet,they contain not more than 110%of the labeled amount.

Edetate disodium titrant— Prepare and standardize as directed in theAssayunderAmmonium Alum.

Assay preparation— Transfer an accurately counted number of Tablets,equivalent to about 665mg of aluminum hydroxide,to a suitable beaker.Add 15mLof hydrochloric acid,and swirl to dissolve the Tablets.Add 80mLof water,and filter into a 200-mLvolumetric flask.Wash the filter with water into the flask,add water to volume,and mix.

Procedure— Pipet 20mLofAssay preparationinto a 250-mLbeaker,then add,in the order named and with continuous stirring,25.0mLofEdetate disodium titrantand 20mLof acetic acid–ammonium acetate buffer TS,and heat near the boiling temperature for 5minutes.Cool,add 50mLof alcohol and 2mLof dithizone TS,and mix.Titrate with 0.05Mzinc sulfate VSuntil the color changes from green-violet to rose-pink.Perform a blank determination,substituting 20mLof water for theAssay preparation,and making any necessary correction.Each mLof 0.05MEdetate disodium titrant consumed is equivalent to 3.900mg of Al(OH)3.

Lanthanum chloride solution— Transfer 17.6g 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 by mixing 226mLof hydrochloric acid with sufficient water to make 1000mL.

Potassium chloride solution— Dissolve 3g of potassium chloride in water in a 100-mLvolumetric flask,dilute with water to volume,and mix.

Magnesium stock 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.Transfer 2.0mLof this solution to a 100-mLvolumetric flask,dilute with water to volume,and mix.This solution contains 20µg of magnesium (Mg)per mL.

Standard preparations— To three separate 100-mLvolumetric flasks each containing 5.0mLofLanthanum chloride solution,add 1.0,2.0,and 3.0mL,respectively,of theMagnesium stock solution.Dilute each with water to volume,and mix.These solutions contain 0.1,0.2,and 0.3µg of magnesium (Mg)per mL,respectively.

Assay preparation— Transfer an accurately counted number of Tablets,equivalent to about 250mg of magnesium hydroxide (100mg of magnesium),to a 1000-mLvolumetric flask.Add 500mLofDilute hydrochloric acid,and swirl to disintegrate the Tablets.Add 100.0mLofPotassium chloride solution,dilute with water to volume,and mix.Transfer 10.0mLof this solution to a 100-mLvolumetric flask,dilute with water to volume,and mix.Transfer 2.0mLof this solution to a second 100-mLvolumetric flask,add 5.0mLofLanthanum chloride solution,dilute with water to volume,and mix.

Blank— Add 50mLofDilute hydrochloric acidand 10.0mLofPotassium chloride solutionto a 100-mLvolumetric flask,dilute with water to volume,and mix.Transfer 10.0mLof this solution to a second 100-mLvolumetric flask,dilute with water to volume,and mix.Transfer 2.0mLof this solution to a third 100-mLvolumetric flask,add 5.0mLofLanthanum chloride solution,dilute with water to volume,and mix.

Procedure— Concomitantly determine the absorbances of theStandard preparationsand theAssay preparationat the magnesium emission line at 285.2nm,with a suitable atomic absorption spectrophotometer (seeSpectrophotometry and Light-Scattering á851ñ)equipped with a magnesium hollow-cathode lamp and an air–acetylene flame,using theBlankto set the instrument.Plot the absorbances of theStandard preparationsversus concentration,in µg per mL,of magnesium,and draw the straight line best fitting the three plotted points.From the graph so obtained,determine the concentration,C,in µg per mL,of magnesium in theAssay preparation.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;andNis the number of Tablets taken to prepare theAssay preparation.

Assay preparation— Prepare as directed in theAssay for aluminum hydroxide.

Procedure— Pipet a volume of theAssay preparation,equivalent to about 50mg of calcium carbonate,into a 400-mLbeaker,and add 200mLof water,a volume of sodium hydroxide solution (1in 2)equivalent to the volume of theAssay preparationtaken,and 250mg of hydroxy naphthol blue.Stir with a magnetic stirrer,and titrate immediately with 0.05Medetate disodium VSuntil the solution is distinctly blue.Perform a blank determination,substituting a volume of water equivalent to the volume of theAssay preparationtaken,and make any necessary correction.Each mLof 0.05Medetate disodium is equivalent to 5.004mg of CaCO3.

Dilute hydrochloric acid— Prepare by mixing 400mLof hydrochloric acid with sufficient water to make 1000mL.

Standard preparation— Transfer about 60mg of USP Polydimethylsiloxane RS,accurately weighed,to a separator,add 30.0mLof chloroform and 60mLofDilute hydrochloric acid,shake for 30seconds,and allow the phases to separate.Remove about 10mLof the lower,organic layer to a screw-capped,15-mLtest tube containing 0.5g of anhydrous sodium sulfate.Close the tube with a screw-cap having an inert liner,agitate vigorously,and centrifuge the mixture until a clear supernatant is obtained (Standard preparation).

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 60mg of simethicone,to a suitable screw-capped bottle,add 30.0mLof chloroform and 60mLofDilute hydrochloric acid,and allow to stand,with frequent shaking,until the Tablets are dissolved.Transfer the contents of the bottle to a separator,shake,and allow the phases to separate.Remove about 10mLof the lower,organic layer to a screw-capped,15-mLtest tube containing 0.5g of anhydrous sodium sulfate.Close the tube with a screw-cap having an inert liner,agitate vigorously,and centrifuge the mixture until a clear supernatant is obtained (Assay preparation).

Blank— Place 30.0mLof chloroform and 60mLofDilute hydrochloric acidin a separator,shake for 30seconds,and allow the phases to separate.Remove about 10mLof the lower,organic layer to a screw-capped,15-mLtest tube containing 0.5g of anhydrous sodium sulfate.Close the tube with a screw-cap having an inert liner,agitate vigorously,and centrifuge the mixture until a clear supernatant is obtained (Blank).

Procedure— Concomitantly determine the absorbances of theStandard preparationand theAssay preparationin 0.5-mm cells at the wavelength of maximum absorbance at about 7.9µm,with a suitable IRspectrophotometer,using theBlankto set the instrument.Calculate the quantity,in mg,of [-(CH3)2SiO-]nin each Tablet taken by the formula: in which Wis the weight,in mg,of USP Polydimethylsiloxane RSused in preparing theStandard preparation;Nis the number of Tablets taken to prepare the Assay preparation;and AUand ASare the absorbances of theAssay preparationand theStandard preparation,respectively.