Abstract
In order to develop a reliable equation of state for a fluid, various thermodynamic property measurements of the fluid are required. Among them, isochoric heat capacities (cv) measurements provide a very useful check for calculations of the second derivative of the pressure with respect to temperature which is challenging to measure accurately. This paper briefly explains principles and problems to measure cv, especially experimental requirements for high pressure fluids. Under high pressures, specialized electronic measuring and control techniques as well as data processing are required. Major adiabatic calorimeters and their constructions are described in accordance with this aspect. Among them, a newly-developed twin-cell adiabatic calorimeter is selected and described in detail. Also, their measurement results which show some interesting behavior of cv are introduced.
