Abstract: In a process for the production of aluminium a molten alumina slag, containing combined carbon is circulated through one or more alternately arranged relatively low temperature zones where carbon is added to increase the combined carbon content of the slag by reaction with the alumina slag and high temperature zones where aluminium metal is released by reaction of aluminium carbide and alumina in the slag with consequent depletion of the combined carbon content. Alumina is supplied to the slag at one or more locations. The energy to drive the reactions is preferably supplied by resistance heating of the slag particularly in transit from a low temperature zone to a high temperature zone although usually additional energy is supplied to the slag in the return from a high temperature zone to the next low temperature zone.In most instances the aluminium-liberating reaction is carried out in an upwardly inclined passage and the gas evolved is employed to achieve the circulatory movement of the slag.

Abstract: In methods of joining metal surfaces involving heating to a temperature above about 560.degree.C, the use of a flux comprising a mixture of potassium fluoaluminates. Particularly for brazing aluminum, a flux consisting essentially of potassium fluoaluminate complexes (e.g. KAlF.sub.4 and K.sub.3 AlF.sub.6) may be employed, having a composition corresponding to an AlF.sub.3 /KF ratio, in parts by weight, between about 65:35 and about 45:55. The flux is essentially free of unreacted potassium fluoride and may be in divided solid form.