154 Journal of the Mitchell Society. [Dec. 



T 8 P 



[3] L = T (V-z.)^. 



[4] h == /*' (f-dT — ^ D") + R. 



[5] L = 2RTlog e ^-. 



Using- the constants we have hitherto adopted, the equa- 

 tions become: 



[6] L = 0.0 4 31833 T (V — v) -|^- cals. 



[7] !/ = /*' W~d — &"W) + 0.0 4 31833 P (V — v) cals. 



r«n t 9.1522 « . rf ., 

 [8] L = T log- -=r- cals., 



ra being- the molecular weig-ht, with oxygen equal to 16 as the 

 standard, and log-arithms to base ten. 



The equations are all theoretically derived. 



Equation 3 rests primarily upon the first and second laws 

 of thermodynamics and is deduced therefrom by a familiar 

 line of reasoning. No assumption is made as to the nature or 

 cause of the latent heat, or as to the nature of the substance 

 itself. The equation will serve as well to calculate the latent 

 heat of fusion or the energy absorbed during the change in 

 the crystalline form of a solid. It merely expresses the 

 energy necessary to effect a change in volume under given 

 conditions, and is silent as to the cause of the change or the 

 nature of the substance. So far as present knowledge goes, 

 there is no need for questioning the correctness of the results 

 obtained by this equation, the data being accurate. We can 

 therefore well use the latent heat so obtained as a check, 

 either upon direct measurements of the latent heat, or upon 

 other calculations involving relations and assumptions, which 

 perhaps are true, but which are not so fundamental. 



We have already published (second paper, Tables 2 to 22; 

 the calculations for six or seven of the substances were, how- 

 ever, the work of others) the results obtained by the applica- 



