Preparation of water soluble polymeric flocculants by photopolymerization of hydrophilic monomers

In a process for the photopolymerization of aqueous solutions of olefinically unsaturated hydrophilic monomers into water soluble polymeric flocculants, by exposing such monomers to photopolymerizing irradiation in the presence of a photopolymerization promoter, the improvement which comprises effecting said photopolymerization with irradiation of a wavelength between about 150 and about 500 m.mu., in the conjoint presence of a solubilization facilitating amount of an organic polyhydroxy compound of the sugar family comprising at least two secondary alcohol functional groups, from 5 to 6 carbon atoms and one or two carboxyl groups or the salt forms thereof, and with the pH of the aqueous monomer solution ranging from 4 to 13.