Bismuth Subsalicylate Magma
» Bismuth Subsalicylate Magma is a suspension of Bismuth Subsalicylate in water that contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of C7H5O4Bi. Bismuth Subsalicylate is a basic salt that when dried at 105 for 3 hours contains not less than 56.0 percent and not more than 59.4 percent bismuth and not less than 36.5 percent and not more than 39.3 percent of total salicylates.
noteDry at 105º for 3 hours to determine the solids content and, after determining the solids content, perform all tests on a portion of the dried magma.
Packaging and storage Preserve in tight, light-resistant containers.
Labeling The label states that this article is not intended for direct administration to humans or animals.
USP Reference standards 11
USP Bismuth Subsalicylate RS.
USP Salicylic Acid RS.
B: It meets the requirements of the tests for Bismuth 191.
Other requirements It meets the requirements for Limit of nitrate, Limit of free salicylic acid, Limit of copper, lead, and silver, and Limit of soluble bismuth under Bismuth Subsalicylate.
Assay for bismuth Using a quantity of dried Magma, equivalent to about 300 mg of bismuth subsalicylate, proceed as directed in the Assay for bismuth under Bismuth Subsalicylate.
Assay for total salicylates
Ferric ammonium sulfate solution, Standard stock solution, Standard preparation, and Blank Proceed as directed in the Assay for total salicylates under Bismuth Subsalicylate.
Assay preparation Using a quantity of dried Magma, equivalent to about 52 mg of bismuth subsalicylate, proceed as directed for the Assay preparation in the Assay for total salicylates under Bismuth Subsalicylate.
Procedure Proceed as directed in the Assay for total salicylates under Bismuth Subsalicylate. Calculate the percentage of total salicylates in the portion of dried Magma taken by the formula:
10,000(C/W)[(AUr AUu B)/(ASr ASu B)]in which W is the weight, in mg, of dried Magma taken to prepare the Assay preparation; AUr is the absorbance of the Reacted assay preparation; AUu is the absorbance of the Unreacted assay preparation; ASr is the absorbance of the Reacted standard preparation; ASu is the absorbance of the Unreacted standard preparation; and B is the difference in the absorption of the Reacted blank solution and the absorption of the Unreacted blank solution.
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USP32NF27 Page 1688Pharmacopeial Forum: Volume No. 33(4) Page 638