AbstractThe solubility of ethylene was measured in water, water–tert‐butyl alcohol, water‐emulsifier, water‐tert‐butyl alcohol‐emulsifier, and water–tert‐butyl alcohol–emulsifier–polyethylene. The polymerization of ethylene in an emulsion system differs from that of other vinyl monomers in several ways: the rate of polymer formation is inversely proportional to the emulsifier concentration and to the number of particles, the molecular weight of the polymer increases as the particle size increases, the polymer contains bound emulsifier whose concentration depends inversely on the particle diameter. These peculiarities are attributed to a transfer reaction between polymer radicals and emulsifier adsorbed on the surface of the polymer particle. In the presence of a fatty‐acid soap, the transfer probably occurs primarily at the carbon α