otherwise be suggested by the drawing the dome 12 is pierced at suitable locations to permit delivery therethrough of aluminum and of oxygen and in the preferred embodiment illustrated of a mixture of oxygen and hydrogen or of oxygen and acetylene or of oxygen and propane or other combination of oxygen and combustible gas more particularly in the preferred embodiment illustrated and being described nozzles 18 and 20 pass through the dome 12 for the delivery of a mixture of oxygen and hydrogen and of oxygen to the space 11 which constitutes a reaction chamber in each case the oxygen is of high purity advantageously there may be for example three nozzles 18 and three nozzles or lances 20 all alternately and equiangularly disposed about the axis of cylinder 10 a further inlet 22 through the dome 12 is supplied also with high purity oxygen to insure a slight supraatmospheric pressure beneath the dome 12 and to insure that the atmosphere there will be oxidizing with an excess of oxygen over that stoichiometrically required for combination with the aluminum which is to be converted to aluminum oxide and also over that required for combustion of any hydrogen acetylene or other fuel supplied at the nozzles 18 the nozzles 18 and 20 sometimes hereinafter referred to as torches and lances respectively may be conventional in construction they are designed each to deliver to the space 11 as a high velocity stream the gas or gases with which they are fed from sources not shown in the drawing these sources may include conventional elements of structure known in the arts of gas welding and metal cutting for mixing.