Study of chlorosubstituted hydroxamic acids for the extraction-spectrophotometric determination of thallium(III) and germanium(IV)

Abstract

A simple, rapid and selective method for the extraction-spectrophotometric determination of thallium(III) and germanium(IV) is described. Thallium and germanium are extracted with a chloroform solution of N-p-chlorophenyl-2-furohydroxamic acid from solutions of pH 7.0 and 6.0 M HCl, respectively. The thallium-hydroxamic acid complex is yellow whilst that of germanium-hydroxamic acid is colourless. Phenylfluorone is added to the germanium-hydroxamic acid extract. The λ_max. and molar absorptivities of the thallium and germanium complexes are 375 and 495 nm, respectively, and 1.4 × 10⁴ and 1.2 × 10⁵ l mol^–1 cm^–1, respectively. Common anions and cations do not interfere in the determination of thallium and germanium and some interfering cations can be masked using suitable masking agents. The spectral characteristics of metal complexes with six chlorosubstituted hydroxamic acids are recorded. Thallium is also determined by AAS and the results obtained are in agreement with the spectrophotometric method. The method is applied to the determination of thallium and germanium in standard samples.