Abstract: A process for treating organic phosphates, comprising(a) mixing a waste organic solvent mainly composed of an organic phosphate with an additive mainly composed of at least one of metal salts of aliphatic carboxylic acids represented by formula:(C.sub.n H.sub.2n+1 COO).sub.m MwhereinM is K, Ca or Al, andm is a positive integer of 1, 2 or 3,(b) heating the resulting mixture, and(c) optionally burning the mixture to form stable solid containing phosphor content. The metal salts of aliphatic carboxylic acid are preferably metal salts of acetic acid such as potassium acetate, calcium acetate and aluminum acetate. Typical organic phosphate solvent is tributyl phosphate or a mixed solution of tributyl phosphate and benzene.