Physical significance of entropy or of the second law

by Joseph Frederic Klein

for all the changes of state will be equal to zero. From this follows at once that if the change of state is not allowed to continue to the restoration of the initial condition (1), but is stopped at any state (2), the value of the sum

will depend solely on the final state (2) and on the initial state (1), and not on the course of the passage from 1 to 2."[28]

"The last expression is called by CLAUSIUS the entropy of the body in state 2, referred to state 1 as the zero state. The entropy of a body in a particular state is, therefore, like energy, completely determined down to an additive constant depending on the choice of the zero state."

(14) "Let us again designate the entropy by

, then

or, what amounts to the same thing, by