Process for isolating 4,4-dihydroxydiphenyl sulfone from a mixture of dihydroxydiphenylsulfone isomers

A process for isolating 4,4'-dihydroxydiphenyl sulfone from a mixture of dihydroxydiphenyl sulfone isomers, which process consists essentially of heat dissolving in phenol and water an isomer mixture consisting of 4,4'-dihydroxydiphenyl sulfone and 2,4'-dihydroxydiphenyl sulfone and then cooling the resulting solution thereby allowing 4,4'-dihydroxydiphenyl sulfone to precipitate as an adduct with phenol wherein the water is present in an amount less than 20% by weight based on the amount of phenol, the dissolving of said isomer mixture is performed at about 60.degree. C. to about 100.degree. C., and the cooling of the resulting solution is performed at a temperature lower than about 50.degree. C.