Comments on the behaviour of some thermodynamic characteristics of single component substance in the region defined by the line of liquid vapor equilibrium

TL;DR

This paper critically examines existing claims about the behavior of thermodynamic characteristics of single-component substances, specifically challenging the positivity of isochoric heat capacity and the negativity of isobaric heat capacity near the spinodal line.

Contribution

It provides a detailed analysis showing that previous statements about heat capacities in metastable and spinodal regions may not be generally valid.

Findings

Isochoric heat capacity can be negative in certain regions.

Isobaric heat capacity may not become negative near the spinodal.

Previous assumptions about heat capacity behavior are not universally correct.

Abstract

It is shown that in general case may be not correct the statements of [1,2,6-8] that 1) the isochoric heat capacity on the entire thermodynamic surface, including the metastable region of states and the region defined by the spinodal, remains positive and finite except for the critical point, and 2) the isobaric heat capacity becomes negative in the region defined by spinodal.