Abstract: An invert microlatex of at least one cationic water-soluble vinyl monomer, if necessary copolymerized with at least one anionic or non-anionic water-soluble vinyl monomer, is prepared by a process consisting in a first stage (a) of preparation of an invert microemulsion (of the water-in-oil type) and a second stage (b) in which the invert microemulsion obtained in stage (a) is subjected to conditions of polymerization, stage (a) consisting in mixing: (A) an aqueous solution of at least one cationic water-soluble vinyl monomer, if necessary mixed with at least one anionic or non-ionic water-soluble vinyl monomer, (B) an oil phase containing at least one liquid hydrocarbon, and (C) at least one non-ionic surface active agent, in a proportion sufficient to obtain an invert microemulsion, and having an HLB, either between 11 and 15 when the cationic water-soluble vinyl monomer is alone or mixed with an anionic water-soluble vinyl monomer, or between 7.

Abstract: Process for the purifiying water using an effective proportion of a flocculating agent consisting of a reverse microlatex comprising a polymer of at least one water-soluble cationic vinyl monomer, which may be copolymerized with at least one water-soluble anionic or non-ionic vinyl monomer, possessing a molecular weight at least equal to 2.times.10.sup.6.The said microlatex is in the form of particles of a microlatex having a diameter of between 30 and 160 nm and its polydispersity index is between 1.05 and 1.2.