Radiochemical investigations of the separation of chemical elements using N-benzoyl-n-phenylhydroxylamine

Abstract

A study has been made of the application of N-benzoyl-N-phenylhydroxylamine (NBPHA) to separations of a number of transition and main group elements by liquid-liquid extraction methods. In general the partition of each element from aqueous hydrochloric or perchloric acid has been examined as a function of acidity, reagent concentration in chloroform (the second phase), rate of extraction and range of metal ion concentration. Where extraction occurred only at low hydrogen ion concentrations an aqueous acetate buffer was employed. Back-extraction into aqueous phases of various compositions was also investigated. Niobium is thus separated from zirconium; niobium, tantalum, protactinium from each other; protactinium from uranium, thorium and its fission products and gallium, indium, thallium, germanium, tin and lead from each other, A comparative study of KBPHA and the ammonium salt of N-nitroso-phenylhydroxylamine (cupferron) in the extraction of tin, antimony, arsenic and bismuth has also been carried out and potential separations with NBPHA noted. Depending on the valency state of tin, cupferron gives two distinct products, while NBPHA gives only a single product in which the valency state of the tin has previously been in some doubt. Partition studies have been devised to examine the dependence of extraction on reagent, chloride ion (a constituent of the product precipitated from hydrochloric acid) and hydrogen ion concentrations. The results in combination with those from infra-red and nuclear magnetic resonance examinations of the product of precipitation show that the substance extracted from 1 M hydrochloric acid is the same as that obtained by precipitation under similar conditions. It is Sn(C(_13)H(_10)O(_2)N)(_2)Cl(_2) which contains tin-(IV). Decomposition products of cupferron were examined using vapour phase chromatographic methods. Some polarographic work on the behaviour of tin and antimony in the presence of KBPHA has been carried out. Methods for the determination of these two elements in mixtures are presented using NBPHA.