Separation of rare earth values by liquid/liquid extraction

A process for the separation of rare earth values from an aqueous solution of the nitrates of at least two rare earth elements, comprising liquid/liquid extracting such aqueous nitrate solution with a liquid organic phase capable of containing high concentrations of the rare earth values which comprises a solvating organophosphorus extractant having the formula (I):

• ##STR2## in which R.sub.1, R.sub.2 and R.sub.3, which may be identical or different, are each a hydrogen atom or a substituted or unsubstituted linear or branched chain, or cyclic, saturated or unsaturated hydrocarbon radical, with the proviso that the total number of carbon atoms in the radicals R.sub.1, R.sub.2 and R.sub.3 is at least 12, and at least two of said radicals are different.