Content Handbook F

Outline of method

93.1 Bismuthate Method

The sample is dispersed in nitric acid, the mixture is boiled, and insoluble material is filtered off. Sodium bismuthate is added, the excess is filtered off, and the filtrate is treated with a measured excess of diammonium iron(II) sulphate solution. The residual iron(II) sulphate is titrated with potassium permanganate.

93.2 EDTA Method

The material is dissolved in a known excess of EDTA solution. The mixture is gently boiled, cooled, and ascorbic acid and ammonia buffer solution are added. The excess EDTA is titrated with magnesium sulphate using mordant black 11.