In a process for preparing a diether of a polyoxy' alkylene glycol by reacting 1) one mole of a monohydroxy compound of the class consisting of aliphatic alcohols and phenols having from 1 to 20 carbon atoms and containing only carbon, hydrogen, and oxygen in the molecule, with no functional group other than the hydroxy group attached thereto with (2) at least 5 moles of at least one essentially a