Abstract: A device for measuring thermal properties of a test substance, which device incorporates a thin element or a layer of an electrically conductive material, e.g. metal, intended to be brought in heat conductive contact with said test substance (3), means for passing an electric current through said element or layer for supplying heat to the test substance and causing a temperature increase therein and instrument for recording the voltage variation over the element or layer as a function of time. In order to increase the characteristic time for the experiments and thereby making it possible to use less sophisticated measuring instruments the active part of said element (6) or layer (4) over which the measurement is made has substantially equal size along at least two lateral dimensions. The element can e.g. be given of square or circular shape.