1197 



then be able to increase with decreasing v, but on the other hand 

 the value of a can also, decrease in consequence of absorption of 

 the lines of force, when v becomes smaller. 



X. The Virial of Attraction. 



Let us first determine the value of the virial of attraction. 



For r = 5 Pr will evidently' be == — M, the (negative) maximum 

 value of the force function. For ƒ (?') is taken so in the virial formula 

 that attraction becomes positive. If e.g. P,. = — c-.ri, (hen ƒ(;•) 

 becomes =z d P,. -. dr ^ qc -. r'i-^^ , hence properly positive. Further 

 Pj. = for r ^ ?'„, where the attraction stops or becomes imper- 

 ceptible, so that the second integral yields: 



MN 



~ M 



And as iV X |-t-^'" is evidently = /Y X '^'^n = {bg)^ [m = volume 

 molecule; the index g refers to infinitely large volume; the index 



QO to infinitely high temperature), we may write {bfi)^ X ( — I = ^'{b</)^ 



for jV X f ^'*i'j and the value of the virial of attraction, as n : JSf= 1 : v, 

 becomes : 



MN 



V 



Let us now put 



MN 

 M^/L^^^^'T^'^^- 1 ) = a, . . . . . . («) 



MN fMN 



then for 7'= oo : 



Hence, when we put MN^o, we get: 



JIrt_ ^ 

 « = «ooX^-^^ = ««X/(a), ..... (i; 



and 



^r,=:-- ......... (2) 



V 



The quantity n is tlierefore determined by 



a = MN = ~^^~ (3) 



