

Temperature of Hydrogen. 273 



only the ideal gaseous laws usually so called, but likewise the 

 well-known general Law of Thermodynamic Correspondence 

 are to a sufficient degree of approximation obeyed by them. 

 Thus, with M to denote the molecular weight, and C a con- 

 stant, of the same value for all bodies, 





(1) 



and if the p, v, t of every gas be expressed as multiples 

 of their critical values p c , v CJ and t c ; that is, if we write 



it = — , (o = — , and t = — , then 



p e v t c } 



7ra) = KT; ....... (2) 



where K is another universal constant. From these equations 

 it follows at once' that 



tc=AMp c v c , . (3) 



where again A is a constant quantity, the value of which is 

 the same for all bodies. Now M. Amagat finds for carbonic 

 acid, 



* c = 273 + 31-35; p c =72'9 atm. ; -=0464^; 



1 v c cm. 



hence, taking one gramme as unit molecular weight and one 

 dyne per cm. 2 as unit pressure, we obtain 



A = 0-4344.1 0- 7 



/abs. degree \ 

 \ erg )• 



The following table shows values of A calculated for 

 several gases : — 



Substance. 



M. 



t . 



c 



A. 



Carbonic Acid, C0 



44 



28 

 64 

 44 

 74 



28 



30435 



283 



429 



309-4 



467*4 



127 



0-4344 . 10~ 7 

 0424 .10~ 7 

 0-436 .10" 7 

 0-389 .10" 7 

 0-430 . 10~ 7 

 0-47 . 10~ 7 



Ethylene, C.JL 



Sulphuric Ether, C 4 H 10 O. . . 

 Nitrogen, N 2 





It will be observed that the differences between the values 

 of A do not appear to be in any connexion whatever with the 

 M J s or t c 's : and, since the accuracy of the experimental data 



