Robkrtson. — Latent Keats of Fusion. 503 



of numbers which appear to be periodic functions of the 



Table I. 



atomic weights : — 



It will be noticed that the values tend to increase from 

 top to bottom and from right to left — e.g., zinc to mercury 

 and iodine to silver. It would seem, therefore, that some 

 periodic quantity must take the place of the v in Crompton's 

 formula to make the relation true for all the elements. 



It can be proved that TS/w = a constant, where S is the 

 specific heat of the element, by using the relation TC = a 

 constant, C being the coefficient of expansion. But Pictet 



proves TC V- = K, the expression V ^ representing the mean 

 distance between the atoms if d is the density. Applying 

 this, it follows that — 



TS V± 



w 



= constant. 



But AS = constant (Dulong and Petit); 



Aw 



— =n=. = constant. 

 • T v'a 



d 



In Table II. are given the values thus calculated for the 

 elements with atomic weights above 40 whose latent heats 

 are known. As in the case of Dulong and Petit's law, the 

 relationship does not hold for the elements with low atomic 

 weights. The values of d are taken at ordinary temperatures 

 for the substances in the solid state, except in the case of 

 bromine, the specific gravity of which in the solid state is 

 unknown. Most of the constants required have been obtained 

 from the papers of Crompton and Deerr, while the values for 

 silver and copper are due to Hey cock and Neville.* 



Trans. Roy a! Soc, 1897, 189, 25. 



