136 MOLECULAK MOTION AND ITS ENERGY 58 



oppositely to the gases investigated byWiillner. Miiller 

 found, as in the table of 55, 



For these substances, therefore, the ratio of the specific heats 

 does not decrease, but increases, as the temperature rises ; 

 and their atomic energy c increases with the temperature not 

 more, but less, rapidly than the molecular energy E. 



Xlt is, however, easy to see that we have here to do 

 ith quite different circumstances ; for the two methyl com- 

 pounds which Miiller examined have not the same right 

 as the five bodies examined by Wiil In er to be considered 

 gases. We can hardly assume that they obey the laws of 

 Boyle, Gay-Lussac, and Avogadro, at least, not at 

 the temperatures at which Miiller made his observations. 

 Deviations from these laws are in most cases to be ascribed 

 to the heat not being sufficient to overcome the cohesion so 

 far that a breaking up into simple molecules of the same 

 kind is attained. In such vapours an addition of heat 

 augments the number of molecules, and the value of the 

 molecular energy thereby increases, and increases, indeed, 

 more rapidly than the atomic energy. M tiller's observa- 

 tions are therefore just as easy to interpret as those made by 

 Wiillner. 



~ At the present stage of our knowledge we shall have 

 /therefore to assume that the law discovered by Clausius, 

 according to which the molecular and atomic energies 

 should bear to each other a ratio that is always constant, 

 holds good in its full strictness only for diatomic gaseous 

 molecules ; for other molecules, however, that ratio is 

 variable with the temperature, and may, indeed, according 

 to circumstances, either increase or decrease as the' tem- 

 perature rises. 



But it can also happen that for diatomic molecules this 

 law does not hold good. For among the gases whose 



