Bromide electrometric method

The USP method (12) for the assay of sulfacetamide is based on nitrite titration followed by electrometric end-point determination using platinum electrodes. A 500 mg quantity of the drug is transferred to an open vessel. 20 ml of hydrochloric acid and 50 ml of water are added, the solution stirred until the content dissolved, cooled to about 15°, and slowly titrated with 0.1 M sodium nitrite. Each ml of 0.1 M sodium nitrite is equivalent to 21.42 mg of C8H10N2O3S. In the BP method (13), sulfacetamide sodium is assayed by amperometric titration. A 0.5 g quantity of the substance is dissolved in a mixture of 50 ml of water and 20 ml of 2 M hydrochloric acid and 3 g of potassium bromide are added. The solution is cooled in ice and sulfacetamide content determined amperometrically by titration with sodium nitrite. Each ml of 0.1 M sodium nitrite is equivalent to 0.02362 g of CsH9N2Na03S. 

The bromine index can be measured by electrometric and coulomelric titration. In the electrometric titration method, a sample is titrated with bromide-bromate solution (0.1 N solution of mixture of potassium bromide and potassium bromate) until the end-point increase in potential remains steady for 30 s. In coulometric titration, a potassium bromide solution is used to titrate the solvent until the bromine concentration increases because it is no longer being consumed by the unsaturation of the solvent. ... 

Iodide ions can be determined quite well with argentimetric titrations. The Volhard method, electrometric endpoint indications, and adsorption indicators work well. The Mohr endpoint indication, however, does not give good results because of the adsorption of the chromate on the silver iodide precipitate. The presence of chloride and bromide ions disturbs the argentimeric iodide determination. 

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