AbstractA study was made of the mutual solubility of ethylene with various polar and nonpolar relatively high‐molecular‐weight organic compounds at temperatures 1° and 10° C. respectively above the critical temperature of ethylene and at pressures up to 1,500 Ib./sq.in.abs. For many compounds Henry's law was found to be applicable for the liquid phase up to approximately two thirds of the critical pressure of ethylene. In the critical region the solubility of ethylene was extremely sensitive to small changes in both temperature and pressure. The various types of phase behavior encountered were classified according to the nonideality involved. The results of this investigation indicate that a gas near its critical conditions is often capable of dissolving relatively nonvolatile materials in sufficient concentrations to warrant consideration of a separation process using such a gas as the extracting medium, namely fluid‐liquid ext