A process for separating rhodium from mixtures thereof, comprising extracting said rhodium with an aqueous solution of a rhodium complexing agent and a solubilizer. A process for preparing aldehydes in the presence of both the complexing agent and the solubilizer is also set forth. The solubilizer is generally selected from salts of carboxylic acids having 8-20 carbon atoms, alkyl sulfonates, alkyl aryl sulfonates, amines and quaternary ammonium compounds of Formula II ##STR1## wherein A is alkyl, alkoxy, hydroxyalkyl, aryl having 6-25 carbon atoms, or R.sup.7 CONHCH.sub.2 CH.sub.2 CH.sub.2 --wherein R.sup.7 is alkyl having 5-11 carbon atoms; B is an alkyl having 1-25 carbon atoms, an aryl having 6-25 carbon atoms, or an .omega.-hydroxy alkyl having 1-4 carbon atoms; C and D are each independently an alkyl or .omega.-hydroxy alkyl having 1-4 carbon atoms or form, together with each other and the bridging N, a 5 or 6 membered heterocyclic ring; E is a halide, sulfate, borate, sulfonate, lactate or citrate; and p is the number of charges on E. The rhodium complexing agent is preferably a triaryl phosphine carboxylate or sulfonate.