1895.] Specific Heats of some Compound Gases. 



323 



From these and the results given in the former paper it is shown 

 that corresponding halogen derivatives of the same hydrocarbon have 

 the same 7, the statement being no longer restricted to the mono- 

 halogen derivatives of the paraffins. 



The equality of the 7*8 of the two dichlorethanes, and of methyl 

 acetate and ethyl formate, shows that the previously investigated 

 case of the two propyl chlorides does not stand alone, but that it is 

 probably true that isomeric bodies in general have the same 7. 



From the results for the substitution products of methane and 

 ethane with more than one halogen in the molecule it is shown that, 

 whether the first chlorine introduced into the molecule alters the 

 value of 7 or not, each chlorine after the first causes a fall in 7. 



SiCU has the same 7 as CC1 4 . SH 2 has nearly the same 7 as some 

 observers have found for OH 2 , but C0 2 and CS 2 differ widely, whence 

 it follows that, just as in the case of hydrogen and chlorine, the pos- 

 sibility of interchange of oxygen and sulphur without altering 7 does 

 not extend to the substitution of two atoms of sulphur for two of 

 oxygen. 



In the paper a proof is given of the formula 



_ 3 p dv 



for calculating /3, the ratio of the rates of increase of intramolecular 

 energy and translational energy of the molecule on a rise of tempera- 

 ture, and the constant ft is given for the gases investigated. 



01 "1 



It is shown that ' is constant for the paraffins and their mono- 



