of Gases and Molecular Force. 519 



we get the following values of the above ratios : — 



31 20 21 24 17 25 



Excepting in the case of hydrogen, where through experi- 

 mental difficulties the value of C is uncertain, the values of 

 the ratio now show a satisfactory approach to constancy if 

 all the difficulties of the comparison are allowed for, and they 

 furnish satisfactory confirmation of the truth of the inverse 

 fourth power law of force. In view of the importance of 

 this confirmation, it will be well to extend it to as many sub- 

 stances as possible, and although we have exhausted the 

 direct experimental determinations of C, there is an indirect 

 method of obtaining some more by means of the results 

 already established. 



For C0 2 , N 2 0, and C 2 H 4 , (2a) 3 (relative) /Mj3 has the values 

 121, 137, and 114, of which the mean is 124; and assuming 

 this to be the value for all compounds, we can obtain from 

 the values of /3 and M the values of (2a) 3 (relative), then 

 those of (2a) 2 (relative) which stands for 



Mi/{10 2 %(l + C/273)}, 



so that with values of rj it is possible to calculate those of C. 

 The following are the data for the gases CH 4 , NH 3 , and SO s , 

 the values of rj being those given by Obermayer from 

 Graham's transpiration experiments. 



CH 4 . NH 3 . S0 2 . 



/3 1-59 1-22 -55 



M 16 17 64 



M/3 25-4 20-7 35-2 



(2a) 2 (relative) 215 188 267 



10 6 »7o •• 104 96 122 



C 215 352 397 



As before, we can compare M/3C and M.H: 



CH 4 . NH 3 . S0 2 . 



M/3C/10 547 729 1399 



Wl .., 2-2 8-5 15 



M/3C/10 2 M 2 Z 25 8-6 93 



As before, we must double the value of the ratio for the 

 compounds NH 3 and S0 2 , but not for CH 4 , because I have 

 shown its characteristic equation to be of the same form as 



