Method and apparatus for evaporating components of multiple substance mixtures and multiple substance systems

For the evaporation of given components from initial multiple-substance mixtures and systems at subatmospheric pressure, individual portions (P1, P2, P3, P4, P5) of the multiple-substance mixture and systems are placed in ring crucibles (17) stacked at several levels. Vapors of the lower-boiling component are drawn off through a vapor exhaust opening in each crucible, while the top ring crucible (17) is closed except for its vapor exhaust opening. In order to obtain products of high purity through short diffusion path lengths and great uniformity of temperature distribution, a) ring crucibles (17) are used which act as susceptors towards alternating electromagnetic fields, b) heat bodies (16, 21) are arranged under and over the crucible stack, and likewise act as susceptors towards alternating electromagnetic fields, c) the ring crucibles (17) and the heat bodies (16, 21) are heated by inductive coupling, doing so d) with such timing that at least one of the given components of the multiple-substance mixture or system is obtained in the greatest possible purity.