The alkylation of various compositions of propane with ethylene at atmospheric pressure in the presence of various concentrations of ortho-phosphoric acids and mixtures of ortho-phosphoric acid and hydrochloric and sulfuric acids as catalyst was investigated. Physical conditions studied were (1) temperature ranging from 40 to 200°C., (2) length of run from six to eight hours, and (5) vapor feed rate from 100 to 200 eubie centimeters per minute. From the results obtained from this research, it is evident that pipe still vapors composed of ethylene and propane cannot be alkylated at atmospheric pressure and relatively low temperatures with the use of 85-100 per cent ortho-phosphoric acid as a catalyst. No mechanism of reaction has been proven. / M.S.