436 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



equilibrium curve iu such a way that its ratio to Ar is nearly constant. 

 There seems no particular reason why this is not as significant a quan- 

 tity on the melting curve as the latent heat. It is true that it does not 

 enter the equations so simply, but the behavior at the points of special 

 interest on the melting curve is just as simple as that of A//. At the 

 critical point, for example, if there is one, where Ay becomes zero, but 



TABLE XIV. 



The Ch/Vxge op Internal Energy of Mercury on Passing from the 

 Liquid to the Solid at Different Temperatures. 



-J- remains finite, it is known that A/T" = 0. In this case A.E = 

 dp 



also. If the melting curve shows a maximum, which is characterized 



(17) 



by Av = 0, and -j- = 0, then AH remains finite, as does also AE, 



UiT 



which in this case equals AIL The trend of AE on the melting curve 

 would seem therefore to be j ust as valuable an indication as the trend 

 of AH as to the possible existence of a critical point or a maximum. 



The present data offer no evidence, therefore, as to the existence of 

 a critical point, except to show that if there is one it must be at 

 pressures higher than can be reached directly. The positive result 

 is obtained, however, that at high pressures there is a reversal in the 

 behavior of the latent heat such as to invalidate Tammann's argument 

 for a maximum. 



As opposed to Tammann's argument for the impossibility of the exis- 

 tence of a critical point solid-liquid, it may be shown that it is 

 possible to conceive of a molecular mechanism by which the contin- 



