764 Sir J. J. Thomson on the 



Thus K, the specific inductive capacity of the gas at 



constant density, may be written 



•88M 2 xl0 36 /1X 



K=a+ Fp (1) 



We shall assume that a is independent of the temperature, 

 it is probably equal to n 2 where n is the refractive index. 

 If a does not depend upon T, we can find the value of M 2 if 

 we know Kj, K 2 , the values of the specific inductive capacity 

 at the temperatures T\ and T 2 , for from the preceding 

 equation we have 



K!-Ei=-8S»xi(F^-y]| - . . (2) 



Badeker (loc. tit.) gives the specific inductive capacity of 

 ■ammonia gas over a range of temperatures from 18°*4 C. to 

 108°'4 C. : from his values I find M = 1*5 x 10-" i8 and 

 42= 1*00051. The experiments on water have a temperature 

 range of only S°'6 C, we cannot therefore expect to get an 

 accurate value of M for this substance. Substituting the 

 values given by Badeker, I find for water M = 5 x 10 -18 , 

 <a = '939. The fact that a comes out less than unity shows 

 that this value of M is too large. We shall probably get a 

 more accurate value if we assume that K — 1 for water is due 

 entirely to the doublets in the molecule, and find the value 

 of M from formula (1) instead of (2) : doing this I find 

 M = 2*lxl0 -18 . Badeker finds that hydrochloric acid gas, 

 the vapours of methyl and ethyl alcohol and sulphur dioxide 

 all show abnormally high specific inductive capacities: the 

 value of M for hydrochloric acid is less than that for ammonia, 

 while that of the alcohols is somewhat greater. The molecules 

 of the elements such as H 2 , 2 , N 2 , Cl 2 give quite normal 

 specific inductive capacities. 



Taking as the criterion for the absence of intra-molecular 

 ionization the existence of the relation K = n 2 , where K is the 

 specific inductive capacity and n the refractive index, the 

 experiments on the specific inductive capacity of gases show 

 that intra-molecular ionization is absent in the gaseous 

 molecules of the gases in column I., while it is present in 

 those under column II. 



I. II. 



CH 3 C1. 

 CHC1 3 (slight). 



H 2 . 



co 2 . 



H 2 0. 



? . 



cs 2 . 



NH 3 . 



%, 



CC1 4 . 



S0 2 . 



He. 



C 6 H 6 . 



HOI. 



Clo. 



CH 4 . 



CH,OH. 



00. 



NoO. 



(VH 5 OH. 



