﻿10 Mr. William Sutherland on tlie 



the law of energy is that of the inverse cube, then 



m x m 2 f{ l/a x + a 2 ) = m^n^ X K 2 /(a! + a 2 )% 



and if we know relative values of a x and a 2 , then iC 2 (a 1 + a 2 ) 3 

 will give relative values of 1 A 2 ??i 1 t?2 2 . 



There are two sources of relative values of the molecular 

 radii a x and a 2 : — first, the viscosity of the separate gases, and 

 in my paper on the Viscosity of Gases and Molecular Force 

 relative values of (2a 1 ) 2 are given as (2a) 2 (relative) ; the 

 second source is values of (3 the limiting volume of a gramme 

 of a substance as obtained from its characteristic equation as 

 a liquid, and given for various substances in the papers on 

 the " Laws of Molecular Force " (Phil. Mag., March 1893) and 

 the " Viscosity of Gases and Molecular Force " (Phil. Mag., 

 Dec. 1893) : if M is the ordinary chemical molecular mass 

 (weight) of the substance, then M/3 is proportional to (2a) 3 and 

 (MyS)i may be taken as giving a relative value of 2a, and then 

 «i + a 2 is given by (M^) i/2 + (M 2 /3 2 )f/2. 



The latter source of values of a is preferable at present, as 

 it yields values for more substances than the former. For 

 the gases of v. Obermayer's experiments we have the following 

 values: — 



H 2 . 2 . N* C0 2 . N 2 0. 



(3 4-3 -604 -81 -09 -66 



M 2 32 28 44 44 



(M/3)*/2... 1025 1-34 1415 166 1535 



There is no direct determination of /3 for CO, but from the 

 molecular domains (volumes) of a number of carbon com- 

 pounds I have deduced 1*35 as an approximate value of 

 (M/3)V2 for CO. With the above values we get for 



10- 1 1 C 2 {(M,A)i/2+(M 2 /3 2 )i/2} 3 



the following values, which are relative values of jA^n^ ; 

 air will be treated as pure N 2 : — 



C0 2 &N 2 . C0 2 &H 2 . C0 2 &N 0. o &H 2 . 2 &N 2 . O 2 &00. 

 656 182 1122 131 282 241 



It should be noticed that these numbers show a large range 

 of value, namely, from 131 to 1122. Now in the paper on 

 the Viscosity of Gases and Molecular Force relative values 

 are given for iA-^ 2 or Am 2 , the corresponding factor in the 

 expression for the attraction between like molecules; they are 

 given as 10 -1 M/3C, which in the notation of this paper would be 



10-iAI (MA)i/2 + (M,|8 I )i/2}* J 

 and are now reproduced for the substances of v. Obermayer's 

 experiments with the addition of an approximate value for CO : 



