60? 



And vel, cveryiliing' seems to point to this that aetnally all snh- 

 stances at snfticienlly low temporal nrc aj)proa('li to tlie type of tlie 

 moii-atomiL' snbstanccs with exceedingly low critical temperature, at 

 which the cpiantity h remains almost unchanged on diminution of 

 the volume from go to ?\, . Instructive are in this respect the tables 

 in I, p. 819 and III p. 1052, and also Poincaué's and Kamerlingh 

 Onnes's remarks in the discussion of Nernst's Report (Conseil Solvay 

 Gei-man edition, p. 241 at the bottom to 242), where it was pointed 

 out that at very low temperature also the molecular heats of air 

 and hydrogen would probably approach to those of monatomic gases. 



The above contradiction is now immediately removed by the 

 assumption that in the raretied gas slate t is not = 4m, but 

 simply = m (the real volume of the molecules, at most enlarged 

 by a certain sphere of influence), while also in the condensed liquid 

 state h^ is =r. m' , {m' ^m) — in such a way that the idea- of 

 immediate contact at v = i\ of the quasi-spherical molecules with 

 small, remaining intermolecular spaces without energy must be 

 replaced by the moi-e rational view of a compact mass of molecules 

 without real interstices, unless they are considered to be the spheres 

 of influence belonging to the molecules, just as for the large volumes. 

 This limiting state might however also be considered as a fictitious 

 state, which may be approached, but which can never be reached 

 entirely. But this is a question which may be left out of consider- 

 ation here. 



The principal thing is that b always remains = m, aiul that on 

 diminution of the volume tn, therefore, only changes in consequence 

 of the increased pressure under which the molecules are then, the 

 less as T is nearer 0, till at last both at z; = tJ^ ( y> = oo) and at 

 T=^ the molecules will occupy their smallest volume b„ = m' , 

 when the atoms or atomic groups inside the molecule have approached 

 each other as closely as possible. 



2. Hence we attribute, as van der Waai.s did in his middle 

 period, when he drew up the so-calle;i equation of state of the 

 molecule, the change of b with v entirely to a real change in con- 

 sequence of the changed internal pressure ') — with rejection of 



1) For a real diminution of the molecule on diminution of v or lowering of T 

 speaks also llie form of the empirical relation h — f(v,T) found by us — see II, 

 p. 931—933, and III, p, 1051—1054. How little the later views of van der 

 Waals and others — in order to make the origiaal equation of state also applicable 

 to the condensed a'as state and llie liquid state — chi'-fly by considering b as a 

 function of v and T (of whatever nature this variability may be) — have yet come 



