The emulsion polymerization of ethyl methacrylate initiated by the potassium persulfate (I) at 50°C in the presence of an anionic detergent (S), i.e., sodium lauryl sulfate at a low monomer/water ratio, has been ineestigated kinetically by the coneentional dilatometric and graeimetric methods in a phosphate buffer solution of pH 6.85. The number of latex particles per mL of the aqueous phase has been estimated by the soap titration technique, and the aeerage number of latex particles (N) per mL of the aqueous phase has been found to be 1014to 1016, depending upon the experimental conditions. At zero coneersion, the rate of polymerization (Vp) may be written aswhere (I) and (S) denote initiator and soap concentrations, re-spectieely. The eiscosity-aeerage molecular weight (M) of the polymer at 28% coneersion has been found to be