610 Mr. Bernard Cavanagli on 



the phase (a). Clearly this covers chemical reactions as well 

 as transferences between phases etc. 



The total Mass increase of the system will be 



m = 2m ia 8n la . (14) 



The total increase of Potential will be 



^ 2 (ltK ( i5 > 



The total Heat Absorption of the isothermal isopiestic change: 



SQ KJSK (i6) 



and the total Dilatation of the system : 



SV: 



= S (£K •• ^ 



It will be seen, of course, that equations (7-17) lead clearly 

 and directly to the general thermodynamic relations 



^(S^) = -i(gV) (19) 



Finally we have the conditions : — 



For conservation of the mass of the system, 



£M = (20) 



For equilibrium (with regard to a particular virtual change) 



Sf = (21) 



II. Molecular Thermodynamics, Value and General 

 Application. 



Strictly general thermodynamics is independent of atomic, 

 ■molecular, or other hypotheses. 



The term " Molecular Thermodynamics " is suggested and 

 used here to signify a slightly less general treatment of 

 thermodynamics which rests upon the molecular theory of 

 matter. In the case of a low pressure gaseous phase the 

 advantage of such treatment was early (though not perhaps 

 explicitly) recognized. 



Planck * first showed how it could be extended to 

 condensed phases in the simple limiting case where one single 



* Loc. cit. chap. v. 



