This invention relates to a process for increasing the melting point of partially brominated diphenyl oxide mixtures having an average bromine content of 7.2 to 7.7. The process comprises: forming a slurry comprised of C.sub.1 -C.sub.4 alkanol and the mixture; maintaining the slurry until the melting point increase which is sought is obtained; and separating the so-treated mixture from the slurry.