Certain features of the entropy of solid and liquid bodies have, however, been derived with the help of ideal gases as temporary auxiliaries. We consider this argument the simplest and therefore now give an outline of PLANCK'S presentation of the matter.[25]
[25]Thermodynamik, 2d Ed., pp. 87-100.
PLANCK'S PROOF THAT ALSO FOR ANY OTHER BODIES THAN GASES THERE REALLY EXISTS A FUNCTION WHICH POSSESSES THE CHARACTERISTICS OF ENTROPY; THE MAIN STEPS ARE NUMBERED
(1) Expression of entropy for an ideal gas and properties of entropy.
where the elastic forces do a
; strictly speaking,
is not differential of