A critical study of Brilliant green as a spectrophotometric reagent: extraction of chloro-complexes of antimony, thallium, gallium and indium, and of tetrabromoindate(III), and improved procedures for the determination of antimony and thallium

Abstract

Use of cerium(IV), instead of nitrite, to oxidise antimony(III) improves the procedure for the determination of antimony with Brilliant green. Antimony(III) is oxidised in 6 M hydrochloric acid solution, the excess of oxidant being reduced with hydroxylammonium chloride. Brilliant green hexachloroantimonate(V) is extracted from 2 M hydrochloric acid solution with two 10-ml portions of toluene, the Brilliant green reagent solution being added to the aqueous solution immediately before each extraction. When a pure sample of dye is used, and the extraction is made rapidly after the addition of Brilliant green, complete recovery of antimony is effected. The recommended procedure is precise and reliable.

A similar procedure based on the extraction of tetrachlorothallate(III) ions gives complete recoveries of thallium and is an improvement on existing procedures. Tetrachlorogallate(III) and tetrachloroindate(III) ions are not completely extracted by toluene, and procedures based on such extractions cannot be recommended.