Materials containing vaporizable substances are exposed successively in at least two treatment chambers (10, 13, 14), which can be closed off with respect to each other, to a series of decreasing pressures and increasing temperatures. The vaporizable substances are exhausted separately from each treatment chamber (10, 13, 14) and at least partially condensed and collected. The solid materials are discharged from the last treatment chamber (14). The treatment chambers (10, 13, 14) can be closed off against each other, against the atmosphere, and against any other units which may be connected to them downline (17, 18) by vacuum valves (11, 12, 115, 16) and are connected to vacuum lines (10a, 13a, 14a) in which condensers (10b, 13b, 14b) and vacuum pumps (10c, 13c, 14c) are installed.