86 



Mr. J. Kam on Molecular Attraction and 



n 1 v c =l, at the temperature T, the temperature of the 

 saturated vapour at the pressure p=l, and for the liquid 

 at the same pressure p and temperature T, the volume 

 is n 2 . v c . In this manner we find for, e. g.\ — 



Table III. 





Pc 





y x = w x . ?> c . 



v 2 =n 2 . v c . 



CO., 



77 

 33-86 



« a = 153-4984 

 » a = -5016 



1-0103 



•5016 v c 



v c = -0066 



Ethyl propionate 



v c = -01482 



»j = 66-716 

 n 2 = -504 



•996 



•504 y c 



Propyl acetate 



34-80 



«! = 69-10 

 » 2 = -504 



1-0116 



•5036 vc 



v c = -01464 



Ether ... 



v c ... -01334 



37-50 



w x = 74-50 

 » a = -503 



•994 



•503 % 



A few examples taken from Table I. (p. 77) will suffice, 

 as all others following the rule 



2pc • w c = 1 

 must necessarily" comply. 



It is interesting to note that n 2 cannot be smaller than m 5, 

 which value is approached as e becomes extremely small, 

 i. e. at very low temperature. 



For gases with T c <273 we have (y. eq. 23 b) 

 %p c . cp c = -75 (constant), 

 273 



We may therefore expect a similar deviation from 1 for 

 the values n^ c and n 2 <f) c . 



E.g., for Hydrogen (T c =39, p c = 20, v=*00264) we find 



273 

 fa = n } . (f> c = -^ . 39-494 . '00264 = '727, 



in which <p c = v c . -^ 



273 



$ 2 = n 2 . cf) c — -K- . • 506 (j> c 



= 7. -506?; c = '5O60 C ; 



for Helium (T e =5, /? c =2*3, v c = -00299) we have 



273 

 0i = ^.^ = — .4. -00299 



a a 273 « 



q> 2 = n 2 . <pc = — k~ • o . t' c 



= '658, 



= 54*6 . '6v c = '6 .0c 



