Hydrolysis of phosphorus trichloride

A process for the controlled hydrolysis of phosphorus trichloride which avoids the formation of lower oxides of phosphorus, phosphines and diphosphines comprising adding phosphorus pentachloride to the phosphorus trichloride in an amount in the range of from about 20 to about 90 percent, by weight of the phosphorus trichloride, to provide a mixture of phosphorus pentachloride and liquid phosphorus trichloride, and then adding water in the form of finely divided droplets over the surface of the phosphorus trichloride while controlling the temperature of the mixture below about 80.degree. C.