Bismuth Subcarbonate
»Bismuth Subcarbonate contains not less than 97.6percent and not more than 100.7percent of (BiO)2CO3,calculated on the dried basis.
Packaging and storage— Preserve in well-closed containers,protected from light.
Identification— It responds to the tests for Bismuth á191ñand for Carbonate á191ñ.
Loss on drying á731ñ— Dry it at 105to constant weight:it loses not more than 1.0%of its weight.
Chloride á221ñ— Mix 5.0g of it with 10mLof water,add 20mLof nitric acid,warm to achieve dissolution,allow to cool,and dilute with water to obtain 100mLof solution.To 6.6mLof this stock solution add 4mLof nitric acid,and dilute with water to obtain 50mLof solution.A15.0-mLportion of this test solution shows no more chloride than corresponds to 70µLof 0.020Nhydrochloric acid (0.05%).
Limit of alkalies and alkaline earths— Boil 1.0g of it with 20mLof a mixture of acetic acid and water (1:1).After 2minutes,cool and filter.Collect the filtrate,wash the residue with 20mLof water,and add the washing to the filtrate.To this solution add 2mLof 2Nhydrochloric acid and 20mLof water.Heat to boiling and precipitate the bismuth by adding hydrogen sulfide.Cool the mixture,and filter.Collect the filtrate,wash the residue with water,and add the washing to the filtrate.Evaporate this solution to dryness on a water bath.To the residue add 0.5mLof sulfuric acid,dry slowly,and cool:the weight of the residue does not exceed 10mg (1.0%).
Limit of nitrate—
Indigo carmine titrant— Dissolve 4g of indigo carmine in 900mLof water,add 2mLof sulfuric acid,and dilute with water to 1000mL.
Standard solution— Prepare a solution of potassium nitrate in water containing 0.0815mg per mL(equivalent to 0.05mg of nitrate per mL).Add 20.0mLof this solution to a 125-mLconical flask (Standard solution).
Test preparation— To 250mg of Bismuth Subcarbonate in a 125-mLconical flask add 20mLof water,and swirl to suspend.
Procedure— To the Standard solutionand the Test preparationadd 0.05mLof Indigo carmine titrant.Carefully add 30mLof sulfuric acid,and immediately titrate with Indigo carmine titrantto a stable blue endpoint.The volume of Indigo carmine titrantconsumed by the Test preparationdoes not exceed that consumed by the Standard solution(0.4%).
Limit of silver— To 2.0g of Bismuth Subcarbonate add 1mLof water and 4mLof nitric acid.Heat gently to achieve dissolution,add water to obtain 11mLof solution,and cool.Add 2mLof 1Nhydrochloric acid,and allow to stand in a dark place for 5minutes.No more turbidity is produced than corresponds to that produced with 10mLof a solution containing 7.87µg of silver nitrate per mLconcomitantly treated with 1mLof nitric acid and 2mLof 1Nhydrochloric acid (0.0025%).
Arsenic,Method Iá211ñ— Prepare the Test Preparationby dissolving 600mg of it in 35mLof 3Nhydrochloric acid.The limit is 5µg per g.
Limit of copper—
Standard solution— To a 100-mLvolumetric flask add 1.34g of cupric chloride,10g of ammonium chloride,and 3mLof sodium metabisulfite solution (275mg per mL).Dilute with water to volume,and mix.This stock solution contains the equivalent of 5mg of copper per mL.Dilute an accurately measured volume of this solution quantitatively and stepwise with 2Nnitric acid to obtain a solution containing the equivalent of 10µg of copper per mL.Mix 0.25mLof this solution and 9.75mLof water (Standard solution).
Test solution— To 5mLof the stock solution retained from the test for Chlorideadd 2mLof 6Nammonium hydroxide,dilute with water to 50mL,mix,and filter.Use the filtrate as the Test solution.
Procedure— To 10mLof the Standard solutionand the Test solutionadd 1mLof a solution of sodium diethyldithiocarbamate (1in 1000):no more color is obtained from the Test solutionthan is obtained from the Standard solution(0.005%).
Limit of lead—
Diluent— Use 6Nnitric acid that is lead-free.
Standard solutions— Prepare a solution of lead nitrate in Diluentcontaining 0.1598mg per mL.This solution contains 100µg of lead per mL.Dilute an accurately measured volume of this solution,quantitatively and stepwise,with Diluentto obtain Standard solutionscontaining 1.0,2.0,and 3.0µg of lead per mL.
Test solution— Dissolve 12.5g of Bismuth Subcarbonate in 75mLof Diluent.Heat to boiling for 1minute,cool,and dilute with water to 100mL.
Procedure— Concomitantly determine the absorbances of the Standard solutionsand the Test solutionat the lead emission line of 283.3nm with an atomic absorption spectrophotometer (see Spectrophotometry and Light-scattering á851ñ)equipped with a lead hollow-cathode lamp and an air–acetylene flame,using a 1:5dilution of the Diluentas the blank.Plot the absorbances of the Standard solutionsversus concentration,in µg per mL,of lead,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 lead in the Test solution.Calculate the percentage of lead (Pb)in the portion of Bismuth Subcarbonate taken by the formula:
C/12,500.
The limit is 0.002%.
Assay— Dissolve about 500mg of Bismuth Subcarbonate,accurately weighed,in 3mLof nitric acid.Dilute with water to 250mL,add 0.3mLof xylenol orange TS,and titrate with 0.05Medetate disodium VSto a yellow endpoint.Each mLof 0.05Medetate disodium is equivalent to 12.75mg of (BiO)2CO3.
Auxiliary Information— Staff Liaison:Lawrence Evans,III,Ph.D.,Scientist
Expert Committee:(PA6)Pharmaceutical Analysis 6
USP28–NF23Page 265
Phone Number:1-301-816-8389