A Theoretical equation for nonequilibrium state of gas is here extended to the liquid state

and a theoretical equation of isobaric liquid specific heat capacity is derived. This equation can be applied to both polar and nonpolar liquids with an average error of 0.85% from 986 experimental data

220 compounds of 32 structural types

Its accuracy is about 10 times higher than that of the Rowlinson-Bondi method

recommended by Reid

et al. It is far better than all other published methods.