( UI ) 



Por small values of .i' this becomes: 



{l—na)(py -\-^{1—cd) 



' S{l-7ia)<f){l-2na)cp)-\ ^^ ^1=0. 



As viz. O) approaches then to Vs» 1 — o){l-{-7i,r) is replaced by 

 1 — to, but 1 — 3co(l-j-?U') has been retained. Further introduction 

 of to = Vs yields : 



v,y^ri-3to(i+n..)j 



from which follows: 



^9'^(l-3to(l+7.^.)^ ^^ ^,_^, 



-3(l-V,,.y)(l-V,,,^), 



or, after division by — Vs ^"^ • 



3to — 1 (1 — V, ii(pY 3 



(- 3ton = ^ '-^-^^ + (1 — V, nw) (1 — V, ««)) . 



If we now put ay = ^/^ (1 -}- d), we get: 



- = ^ , '' y -] (1 — 7, 7ig)) (1 - 7, n(p) — 71, . (la) 



as we may put 3 ion = n. Tiius we have separated in the first 

 member the only term in which numerator and denominator approach 

 to 0, whereas, in the second member all infinitely small terms have 

 been neglected by the side of those of finite value. 



Formula (la) indicates, in what way the volume v varies in the 

 neighbourhood of x = with x, when we viz. vary the temperature 

 in such a way that we remain in a plaitpoint. 



3. Let us now introduce the temperature. 

 For this the relation holds : ^) 



RT=z-^ L- (1 — A') <9« + rt {d — hyl (2) 



Here is again = av — ^[/a. Reduction gives successively : 



X (1 - cc) U - nio {<f + .^0 J + (y + ^^f fl - ü> (1 + nx)J\ 



and 



RT = — o) 



b. 



1) 1. c. p. 33. 



