Solvent Extraction of Indium

Abstract

THE separation and determination of small amounts of indium in the presence of other metals, especially beryllium and iron, are analytical problems of importance for which no entirely satisfactory solution has as yet been published. Mathers and Prichard¹ precipitated iron as its cupferrate; but some 4 per cent of indium is co-precipitated. May and Hofmann² extracted indium together with some other metals as oxinates into chloroform, decomposed these complexes and then re-extracted indium with a mixture of cupferron and dithizone, neither reagent alone being entirely satisfactory; but this complicated procedure may lead to considerable losses of indium. It may be inferred that the problem was not solved in the Manhattan Project³. In the separation of fission products, indium has been precipitated with cadmium as its sulphide and then separated as its basic acetate⁴, but the chemical yields are only 50–60 per cent. Milner⁵ has recently described a procedure in which indium and iron are separated from beryllium by extraction into chloroform as oxinates. After decomposing these oxinates, ferric chloride is extracted into ether from concentrated hydrochloric acid, and the residual indium determined polarographically.