The third general method of calorimetry, that based on the transformation of some other kind of energy into the form of heat, rests on the general principle of the conservation of energy, and on the experimental fact that all other forms of energy are readily and completely convertible into the form of heat.
The equation of energy is dQ=dE+pdv, (17) expressing that the total energy dQ is used partly in increasing the internal energy of the gas, and partly in expanding the gas against the pressure p. If we take p = RNT/v from equation (14) and substitute for E from equation (16), this last equation becomes dQ 2 (n +3)RNdT +RNTdv (18) which may be taken as the general equation of calorimetry, for a gas which accurately obeys equation (14).
But, Quite Apart From This, Electrical Methods Possess The Greatest Value For Calorimetry, On Account Of The Facility And Accuracy Of Regulating And Measuring The Quantity Of Heat Supplied By An Electric Current.
These subjects are discussed in the articles Density; Thermometry; Calorimetry; Diffusion; Conduction Of Heat; and Condensation Of Gases.
This has been confirmed by scanning differential calorimetry (DSC ).