Abstract: The invention relates to a method for the vacuum distillation of a liquid, in particular by means of a rotary evaporator, wherein at least one fraction of the liquid is evaporated at a reducing pressure, a vapor temperature correlating with a boiling temperature is determined by means of a temperature sensor and a pressure present at the time of the determination of the vapor temperature and correlating with a boiling pressure is determined and a minimal pressure, which may not be undercut in the distillation, is automatically determined by using the determined vapor temperature and to the determined pressure.