Abstract: A general-purpose apparatus for thermochemical quantitative analysis, operable upon the principle of measuring temperature variations accompanying chemical reactions between a solid and a liquid substance as well as between two solutions. An exchangeable reaction vessel made of formed polystro in Dewar vessel is received in a heat-insulated receptacle with a thermostat controlled bath, the reaction vessel being provided with a cover having an opening for a removable lid which supports a temperature sensor and a stirring rod. The removable lid has openings to receive a dose feeder for a solid specimen and/or a dose feeder for reagent solutions.