316 



— ( — !— =: 72, -^- -^ = 71, — ; therefore with the same approxi- 

 dn\ a J v,* a, a 



Illation as (3a) : 



/ 2RT\ 2RT 



We now dnlj get again n^tiv^ -\- ii^Av^ = Avj, because 



a a a 



4. Substitution of (3^) in (1). 



We get for in, after substitution of (3«) in (1), with omission of 

 the external pressure p : 



10 r=: w, n 



— ^ ; — r; — '*i"» rr; ^i ~^j ^ 



or 



w = 7J, n. 



1, ?;/ü/ 1— 7?^ ft^/^° 



1-7, m 



when "27,.^ 1/(2 is substituted for y^a^. With ??i = 7, and v^v^, this 

 passes into 



r 1 n 



w = -^^(t',V« -f/i/«.)l (^V« -t^^V^,)- t(^/-^')i/^ 





 ^ V V 

 "^i '^a 



The factor '/^ is, of course, somewliat different, when m = ^/j' 

 is not = 72- When the critical pressures are equal, the foregoing 

 factor is = 0, hence also the total heat of mixing. But when these 

 pressures do not differ too much, the first term between [ ] will 

 all the same be small with regard to the second, and in approxi- 

 mation 



may be written. 



But however this be, we shall always be allowed to write: 



w =^ n, JK : \ w. = n, '" "' 



or, as V, = Ji.v," + n,v/ = {i—a-)v,' + .w/ = v," + a'{v,'—v,'') = 



