On determining absolute entropy without quantum theory or the Third Law of thermodynamics
arXiv:1510.02311 · doi:10.1088/1367-2630/18/4/043022
Abstract
We employ classical thermodynamics to gain information about absolute entropy, without recourse to statistical methods, quantum mechanics or the Third Law of thermodynamics. The Gibbs-Duhem equation yields various simple methods to determine the absolute entropy of a fluid. We also study the entropy of an ideal gas and the ionization of a plasma in thermal equilibrium. A single measurement of the degree of ionization can be used to determine an unknown constant in the entropy equation, and thus determine the absolute entropy of a gas. It follows from all these examples that the value of entropy at absolute zero temperature does not need to be assigned by postulate, but can be deduced empirically.
arXiv comment16 pages, 2 figures; minor clarifications in v.2; additional ref in v.3