Molybdenum-tungsten-alloys are mainly used in the chemical apparatus construction for melting of glass or metal alloys and in nuclear power engineering for high temperature applications. Frequently, these alloys are not recycled because of their poor separability by hydrometallurgical methods, their high melting point and chemical stability. In this thesis a technology for the separation of the alloying elements in form of their oxides is used. To accomplish this, differences in their respective vapour pressures were used. For instance, these both oxides, MoO3 and WO3, exhibit boiling temperatures of 1.068 respectively 1.841 °C. The trials were performed with variable grain sizes, temperatures and oxygen contents of the atmosphere. The tests were followed by analysis of the effect of these parameters on oxidation time and partition ratios of the respective oxides. The trials were completed by a trial in a rotary kiln to verify the results under practical conditions.