314 



RT 



n,n. 



a a, a 



n.v," + 2 («, + n,) v," v," + n, v," ] a, a, — 



n^ V,' «i' -h 2 (71, v/' a, -f 71, v/ a,) l/a,a, + «, u/ a,' 

 i2T 



/2T 



RT 



4- 7i, L/a, l/a.Ur," + 2t,/) ^/a,-2r/ [/a,^-v/a,' j 

 7?, 2ü/a,V/aj(t;,Va,-i;,V«,)+«i(i'/\-t'/'a,) + 



a a, a. 



For the form between [ ] we may fnrthei- write: 



71, a, (u/|/a,-{-ü,V«i) — «j«i,(yiV«, + f',V«i) — 2wiV,»a,l/a,+2n,f/a,l/a, 

 =: — 71, a, (v/ l/«, -u,' ^/a^) — n,a, (r/ ^/a, — t»," |/a,) + 

 + 2 a, l/a, (n,»,' + 7i,v,') — 2 a, ^/a, (n^v^° + "j»^,'), 

 SO that we finally get: 



/ 272r\ RT r 



r2«o(v/«. 



-- l/«J l/«,«, — (w,«i + w,rt,) (ü," v/a, — V,* l/flj) 



(3) 



This almost quite exact result (only p has been neglected, and in 

 the 1^^ member Av by the side of 2v) shows that Av will be of 

 the order rf = v/V^oj, — y,"|/(2,, so that lu consists of two parts, of 

 which the first is of the order cf' (cf. equation (1)), the second of 

 the order <f. When the critical pressures differ little, d" is very small, 

 and of the small heat of mixing iv the second part (neglected before) 

 will certainly predominate. 



In the case tliat the critical pressures dijer little, expresion (3) 

 can be considerably simplified. For then Vi'y/a^ — Vj'^/a, =: can 

 be put between [ j, and there remains: 



