Abstract: An apparatus for raising a liquid to a given temperature and for controlling and regulating this temperature has a vertical cylindrical enclosure, a vertical tube housing a heating resistor, and a first and a second ferrule located in this order between the tube and the enclosure to define a first, a second and a third annular space. The first ferrule is connected to the lower wall of the enclosure. The tube and the second ferrule are connected to the upper wall of the enclosure. The liquid is supplied to the lower portion of the first space and extracted from the upper portion of the third space. The length of the resistor is shorter by at least one quarter of the height of the tube and orifices in the lower portion of the first ferrule produce a thermosiphon effect between the first and second annular spaces.