The behaviour of the phosphine oxides Cyanex 923 and Cyanex 925 in the recovery of gold(I) from cyanide solutions is described. Extractions are studied as a function of several variables such as temperature, diluent aromaticity, ionic strength and extractant concentration. Gold(I) stripping can be accomplished effectively with low aqueous ionic strength solutions and at high temperatures. From the experimental results it is seen that Me+... Au(CN)2-.3R3PO, where Me+ = Li+ and R3PO = the phosphine oxide, is extracted into the organic phase. The extracted species is probably solvated by water.
