Method and device for determining the concentration of substances in a volume of liquid

Determining the concentration of a material in a liquid volume comprises coupling a calorific output to the liquid volume having a time-dependent progression; measuring a time-dependent temperature progression or single values of the progression on or in the liquid volume; and determining the concentration of the material in the liquid volume from the time-dependent temperature progression or the single values of the progression by considering the prescribed time-dependent progression of the calorific output. An Independent claim is also included for an apparatus for determining the concentration of a material in a liquid volume comprising a container (5) for the liquid (3); a heating element (1) for subjecting the liquid to a calorific output; and a thermocouple (2) for measuring a time-dependent temperature progression.