AND OF THE SECOND LAW 91 



PART V 

 REACH AND SCOPE OF SECOND LAW 



SECTION A 

 ITS EXTENSION TO ALL BODIES 



CLAUSIUS extended the operation of the Second Law or, what 

 is the same thing, the scope of entropy, to aU bodies. See RUHL- 

 MANN'S " Handbuch d. mech. Warmtheorie," Vol. I, pp. 395-405. 



BOLTZMANN says in this connection: " As regards entropy, 

 solid and liquid bodies do not differ qualitatively from perfect 

 gases; the discussion of the entropy of. the former, however, 

 presents greater mathematical difficulties." 



Certain features of the entropy of solid and liquid bodies 

 have, however, been derived with the help of ideal gases as tem- 

 porary auxiliaries. We consider this argument the simplest and 

 therefore now give an outline of PLANCK'S presentation of the 

 matter. 1 



PLANCK'S PROOF THAT ALSO FOR ANY OTHER BODIES THAN GASES 

 THERE REALLY EXISTS A FUNCTION WHICH POSSESSES THE CHAR- 

 ACTERISTICS OF ENTROPY; THE MAIN STEPS ARE NUMBERED 



(i) Expression of entropy for an ideal gas and properties of 

 entropy. 



(2) (a) 5M(C.logr+^logv+const); , . (34) 



() JS-- - ........ (35) 



Thermodynamik, 2d Ed., pp. 87-100. 



