A: It meets the requirements of the tests for Bismuth 191.

B: After acidifying with nitric acid, it meets the requirements of the test for Salicylate 191 with ferric chloride TS.

Standard preparation— Transfer about 500 mg of bismuth, accurately weighed, to a 200-mL volumetric flask, dissolve in 12 mL of nitric acid, and dilute with 0.01 N nitric acid to volume. Transfer 10.0 mL of the solution so obtained into a 500-mL volumetric flask, and dilute with 1 N nitric acid to volume to obtain a concentration of 50 µg of bismuth per mL.

Assay preparation— Transfer an accurately weighed portion of finely powdered Tablets, equivalent to about 90 mg of bismuth subsalicylate, to a 200-mL volumetric flask, add about 150 mL of 1 N nitric acid, and sonicate for 2 minutes. Dilute with 1 N nitric acid to volume. Transfer 20.0 mL of the solution so obtained to a 100-mL volumetric flask, and dilute with 1 N nitric acid to volume. Centrifuge a portion at 4500 rpm for at least 10 minutes.

Procedure— Transfer 10.0 mL, accurately measured, of the Assay preparation and the Standard preparation to separate 50.0-mL volumetric flasks. Add 10.0 mL of 10% ascorbic acid solution and 25.0 mL of 20% potassium iodide solution into each volumetric flask, and dilute with 1 N nitric acid to volume. Concomitantly determine the absorbance of the solutions at the wavelength of maximum absorbance at about 463 nm with a suitable spectrophotometer using the combined reagent solutions as the blank. Calculate the quantity, in mg, of bismuth subsalicylate (C7H5BiO4) in the portion of Tablets taken by the formula: in which, 362.09 and 208.98 are the molecular weights of bismuth subsalicylate and bismuth, respectively; C is the concentration, in mg per mL, of bismuth in the Standard preparation; D is the dilution factor of the Assay preparation; and AU and AS are the absorbances of the solutions from the Assay preparation and the Standard preparation, respectively.