Pyrophosphates

A mixture of compounds comprising

• I. a mixture of different compounds, each having the formula ##STR16## II. a compound or mixture of compounds, each having the formula ##STR17## where R is an alkyl or oxyalkylated alkyl radical having at least 7 carbon atoms, X is oxygen or sulfur, each of said compounds in I containing both oxygen and sulfur, and the compound or mixture of compounds I being the major component of said mixture, M is hydrogen or a metal, said mixture of compounds I and II being prepared by an alcohol or a mixture of alcohols with P.sub.2 S.sub.5 first to form O,O-disubstituted dithiophosphric acid or a mixture thereof until most of the P.sub.2 S.sub.5 has dissolved and the evolution of H.sub.2 S has subsided and then continuing the reaction to shift the equilibrium in favor of converting dithiphosphoric acid or a mixture thereof to the pyrophosphates, with the proviso that, where M is a metal, dithiophosphoric acid or a mixture thereof is neutralized with a salt-forming base or by double decomposition.