Abstract: The invention relates to a process for separating a mixture containing phosphoric acid monoalkylesters, phosphoric acid dialkylesters and minor proportions of diphosphoric acid dialkylesters, each with 6 to 12 carbon atoms in the alkyl radical, by extractively distributing them between an aliphatic or aromatic hydrocarbon as an unpolar solvent and a polar solvent. To this end, the invention provides: for the ester mixture to be admixed with the quantity of water stoichiometrically necessary for hydrolyzing the P-O-P-bond of the diphosphoric acid dialkylester with the resultant formation of the phosphoric acid monoalkylester; for the whole to be maintained for at least 1 hour at temperatures higher than 60.degree. C.