Isobaric heat capacity coefficients for water and argon along their liquid–vapor and liquid–solid coexistence curves

Dependencies of the isobaric heat capacity coefficient (∂S/∂T)P vs the temperature T, pressure P, and chemical potential μ for water and argon in liquid state along their liquid–vapor and liquid–solid coexistence curves were analyzed. Considerations were based on the principle of corresponding states. Observed (∂S/∂T)P temperature dependencies were complicated non-monotonic functions and they were thermodynamically similar for the water in the liquid–ice VII phase transition region and for argon in the liquid–solid phase transition as well as in the liquid–vapor phase transition region for water and argon from the critical point to the triple point. The baric dependencies formed the loops. The dependencies of the (∂S/∂T)P vs the chemical potential in the liquid–vapor phase transition region from the critical point to the triple point were thermodynamically similar for water and argon.