Thallimetric oxidations-VI Titrimetric and spectrophotometric methods for the determination of phosphite and analysis of binary mixtures of phosphite and oxalate.

Titrimetric and spectrophotometric methods have been developed for the estimation of phosphite at mmole and mumole levels, respectively. Thallium(III) is used as an oxidant and the thallium(I) produced is determined either oxidimetrically with potassium bromate or by measurement of the absorbance of thallium(III) at 260 nm in the presence of 0.1 M hydrochloric acid and 1 M perchloric acid. Based on the fact that phosphite and oxalate are oxidized under different conditions, methods are described for the analysis of binary mixtures of phosphite and oxalate. A method is also described for estimation of thallium(III) with phosphite as reluctant, and is applied for analysis of mixtures of thallium(I) and thallium(III).