A: To a mixture of 5mLin 10mLof 3Nhydrochloric acid add 5drops of methyl red TS,heat to boiling,add 6Nammonium hydroxide until the color of the solution changes to deep yellow,then continue boiling for 2minutes,and filter:the filtrate responds to the tests for Magnesium á191ñ.

B: Wash the solids on the filter obtained in Identificationtest Awith hot ammonium chloride solution (1in 50),add 10mLof 3Nhydrochloric acid,and filter:the filtrate responds to the tests for Aluminum á191ñ.

C: Transfer the filter paper and contents from Identificationtest Bto a small platinum dish,ignite,cool in a desiccator,and weigh.Moisten the residue with water and add 6mLof hydrofluoric acid.Evaporate to dryness,ignite for 5minutes,cool in a desiccator,and weigh:a loss of more than 10%in relation to the weight of the residue from the initial ignition indicates SiO2.

Edetate disodium titrant— Prepare and standardize as directed in the Assayunder Ammonium Alum.

Assay preparation— Transfer about 10g of well-shaken Oral Suspension to a tared beaker,and weigh accurately.Add 50mLof water and 10mLof hydrochloric acid,and digest on a steam bath for 1hour.Cool,and filter into a 200-mLvolumetric flask,washing the filter with water into the flask.Dilute with water to volume,and mix.

Procedure— Pipet 20mLof Assay preparationinto a 250-mLbeaker,add 20mLof water,then add,in the order named and with continuous stirring,25.0mLof Edetate disodium titrantand 20mLof acetic acid–ammonium acetate buffer TS,and heat near the boiling point 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 the Assay preparation,and make any necessary correction.Each mLof 0.05MEdetate disodium titrantconsumed is equivalent to 3.900mg of Al(OH)3.

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

Procedure— Pipet 20mLof Assay preparationinto a 400-mLbeaker,add 180mLof water and 20mLof triethanolamine,and stir.Add 10mLof ammonia–ammonium chloride buffer TSand 3drops of an eriochrome black indicator solution prepared by dissolving 200mg of eriochrome black Tin a mixture of 15mLof triethanolamine and 5mLof dehydrated alcohol,and mix.Cool the solution to between 3and 4by immersion of the beaker in an ice bath,then remove and titrate with 0.05Medetate disodium VSto a blue endpoint.Perform a blank determination,substituting 20mLof water for the Assay preparation,and make any necessary correction.Each mLof 0.05Medetate disodium consumed is equivalent to 6.521mg of Mg2Si3O8.