Tris(n-octyl)arsine oxide (tocaso) as a reagent for liquid-liquid extraction—1 extraction of mineral acids

Solutions of tris(n-octyl)arsine oxide (TOCASO), (n-C8H17)3AsO, in benzene have been equilibrated with aqueous solutions of perchloric, hydrochloric, hydrobromic, hydriodic and nitric acids. In the perchloric acid system, the co-extraction of water was noted and the adduct was of the type TOCASO·H3O+ClO4−. Hydrochloric acid formed a 2:1 adduct with TOCASO at aqueous acid concentrations ≧ 1 M. The hydrochloric acid adduct was presumably of the type TOCASOH+HCl2−. Hydrobromic and hydriodic acid formed 1:1 adducts at initial aqueous acid concentrations of 0·1 to 2·0M. The co-extraction of 1 mole of water with each mole of acid was observed under these conditions. At acid concentrations ≧4·0M and ≧7·0 M the adducts, TOCASOH+HBr2− and TOCASOH+HI2− were formed without co-extraction of water. Nitric acid formed a 1:1 adduct at initial acid concentrations of 0·1 to 1·0 M with co-extraction of water. As the nitric acid concentration was increased the ratio of acid to reagent increased while the ratio of water to acid decreased concurrently.