<PICT:0393317/IV/1> Ethylene is separated from its homologues, for instance from industrial gases containing olefines such as oil cracking gases by absorbing the ethylene in an ammoniacal cuprous solution and recovering it therefrom by heating and/or reduced pressure. The gases before or after treatment with the cuprous solution may be treated with a solvent for propylene such as kerosene, and the propylene is recovered therefrom by heating or reduced pressure. The absorption of the ethylene and propylene may be effected under pressure preferably of the order of 20 atmospheres, and the recovery of the dissolved gases may be effected by reducing the pressure in stages. The cuprous solution may be made by dissolving cuprous oxide in aqueous formic acid, and adding ammonia. In an example, an oil cracking gas is washed in a tower 2, as shown in the Figure, with a counter-current of kerosene, the exit gas passing by a pipe 3 to a tower 4 in which it meets the cuprous solution. The kerosene from the tower 2 is passed through two "let down" vessels 5, 6 in which the pressure is successively reduced and then returns to the tower 2. The gas liberated in the vessel 5 which retains most of the ethylene that has dissolved with the propylene, is returned to the compresser 1 which supplies the raw gas to the tower 2. The gas liberated in the vessel 6 contains a high proportion of propylene and may be used as a source of propylene compounds. The cuprous solution from the tower 4 is passed through "let down" vessels 10, 11 in which the pressure is reduced in stages, and then through a heater 12 to a regenerating vessel 13 and is returned to the tower 4. The gas liberated in the vessel 10 is passed back to the compresser 1; the gas liberated in the vessels 11, 13 is the enriched ethylene which is the product of the process. Another modification is described in which the kerosene washing is applied subsequently to the cuprous solution washing. Particulars are given of the composition of the gases at the various stages of the process. Specification 390,863 is referred to.ALSO:<PICT:0393317/III/1> Ethylene is separated from its homologues, for instance, from industrial gases containing olefines such as oil cracking gases, by absorbing the ethylene in an ammoniacal cuprous solution and recovering it therefrom by heating and/or reduced pressure. The gases before or after treatment with the cuprous solution may be treated with a solvent for propylene such as kerosene, and the propylene is recovered therefrom by heating or reduced pressure. The absorption of the ethylene and propylene may be effected under pressure preferably of the order of 20 atmospheres, and the recovery of the dissolved gases may be effected by reducing the pressure in stages. The cuprous solution may be made by dissolving cuprous oxide in aqueous formic acid, and adding ammonia. In an example, an oil cracking gas is washed in a tower 2, as shown in the Figure, with a counter-current of kerosene, the exit gas passing by a pipe 3 to a tower 4 in which it meets the cuprous solution. The kerosene from the tower 2 is passed through two "let-down" vessels 5, 6 in which the pressure is successively reduced and then returns to the tower 2. The gas liberated in the vessel 5 which contains most of the ethylene that has dissolved with the propylene is returned to the compresser 1 which supplies the raw gas to the tower 2. The gas liberated in the vessel 6 contains a high proportion of propylene and may be used as a source of propylene compounds. The cuprous solution from the tower 4 is passed through letdown vessels 10, 11 in which the pressure is reduced in stages and then through a heater 12 to a regenerating vessel 13 and is returned to the tower 4. The gas liberated in the vessel 10 is passed back to the compresser 1; the gas liberated in the vessels 11, 13 is the enriched ethylene which is the product of the process. Another modification is described in which the kerosene washing is applied subsequently to the cuprous solution washing. Particulars are given of the composition of the gases at the various stages of the process. Specification 390,863, [Group IV], is referred to.