;j6 



For an ordinary substance {f =:= 7,2) 

 „ Argon (ƒ = 6) 



,, ideal substance (/'' = 4) 



1,8 = 



1,5 = 



1,11 



2 

 1,33 



2 



==1,^ 



= 1,5 



= 1 



in which the value of z in the first member was calculated from 

 (9), i. e. from z = 2 (1 + y) : r. 



The relation (10) seems, therefore, to hold very accurately. It 

 comes to this that r — 1 = 2 : z, or 



vk - h 2 b. 



hk 



hence 



Vk 



hk 



hk = 2 h. 



(11) 



If, namely, only for ideal substances we find vk — bi, = 2bi,-, so 

 that then ?;/, becomes 3 ^^^ — now this property appears to continue 

 to hold for all substances, if only in the second member 2 b^ is 

 substituted for 2 bk (in which b, is therefore always the volume i\ 

 at T=0 extrapolated from the equation of the straight diameter). 

 As therefore 



Vk hk 



= 2 or 



h. b. 



2 



(11a) 



and as vi, : ^o = 2 (1 + v) according to (9'), we also have simply : 



hk 



^ — _ — 2 V 



6„ 



(12) 



x\nd this is wdiat the new-found relation really comes to. In this 

 waj^ we have for 



Ordinary substance 



Argon 



Ideal substance 



r = 0,9 

 r = 0,75 

 r = 0,5 



z = l,S 

 s = l,5 

 z = l 



For an ideal substance we take y = 0,5, because there just as 

 for the other substances the coefficient of direction has been taken 

 of the straight line which connects the critical point with the point 

 d^ at m = 0. The always slightly deviating direction of the locus 

 1 ( J^ _j_ (/ J — ƒ (m) close to the critical point would be = 0,4. (Cora- 

 pare my earlier papers of 22 Nov. 1911, p. 438 et seq , of 24 Jan. 

 1912, p. 563 et seq. and 574, and of 25 April 1912, p. 1091 1096). 

 That the so-called "straight diameter" really exhibits a slight curvature 

 at the last moment in tiie immediate neighbourhood of the critical 



