24 PHYSICAL PROPERTIES AND COMPOSITION 

 and since 



v M 

 Vk = W 



the fundamental equation becomes 



MP k 



TTr = 22 * 



UicJ-k 



For carbon tetrachloride 



22 x 0-556 x 556 

 < = - = I i , 



44.9 



for acetic acid 



Whilst, therefore, carbon tetrachloride behaves normally, 

 the result indicates that acetic acid in the critical state 

 contains double molecules, as also follows with certainty 

 from the vapour density, and from investigation of solu- 

 tions in hydroxyl free solvents such as benzene. 



3. Corresjjonding States. 

 If in the characteristic equation 



pressure, volume, and temperature are expressed in terms 

 of the critical values as units, i. e. 



P=aP k , V=(3V k) T=yT k> 

 and a, b and R eliminated, then since (p. 21) 



= 3 F, 2 or a = 3 VJP k ; 



*t 



V k = 3 b or 6 = iF,; 



. 



C - 



