An absolute temperature scale independent of the thermometric properties of the working substance. On this scale, the difference between two temperatures T1 and T2 is proportional to the heat converted into mechanical work by a Carnot engine operating between the isotherms and adiabats through T1 and T2. A gas thermometer utilizing a perfect gas has the same temperature scale. For convenience the Kelvin degree is identified with the centigrade degree. The ice point in the Kelvin scale is 273. 16 K. See absolute zero; see also centigrade temperature scale.