Atomic Laws of Tliermocliemistry . 11 



Table I. {continued). 



Fifth family and Arsenic sub-family. 



Di. As. Sb. Bi. 



T 1200 773 710 540 



M/p 22-3 132 179 21*1 



M.H 357 12-2 164 161 



L(kcal.) 38-2 21*9 21'8 18'2 



Eighth family — Iron, Palladium, and Platinum groups. 



Fe (Ni Co). Pd (Eu Eh). Pt (Os Ir). 



T 2080 1775 2050 



M/p 7:2 92 91 



Wl 16-9 206 26-1 



L(kcal.) 56-1 53-2 68*2 



The first fact deserving attention in this table is that in 

 each main family MIp/J or L, the latent heat of vaporization 

 per gramme-atom due to molecular force, is constant. Thus, in 

 the first family it is about 8' 7, and in Cu and Ag about 37 or 

 about four times the value in the main family ; in the second 

 familv the value is about 23*6, and for Zn and Cd about 18*5, 

 which is much nearer to the value for the main family than 

 was the case with Cu and Ag, a fact that is probably con- 

 nected with the greater chemical similarity of Zn and Cd to 

 the main family than is the case with Cu and Ag. The third 

 main family is represented in the table by only two members, 

 Al and La, which have practically the same value for L, the 

 mean being 26*0, while in the related sub-family Ga has 

 a value which is one third of this, just as that for Hg is one 

 third of that in its main family ; In has a value which is 

 nearly a half of that in the main family. At the fourth 

 family we reach a point of transition, after which the sub- 

 families have more the character of main families than the 

 main families themselves. In the fourth main family we have 

 but the one value, that for Ce, about 32, of which the value 

 16 for Sn in the sub-family is one half. In the fifth sub- 

 family As, Sb, and Bi have nearly the same value, about 21, 

 which is nearly one half of the 38 for Di in the main family. 

 For Fe, Pd, and Pt the values are about 60. It is interesting 

 to note how the latent heat per gramme-molecule due to 

 molecular force increases with the valency or order of the 

 main family. To bring this out more clearly the following 

 little table is drawn up, containing in the first row the mean 

 values of L, the latent heat per atom in each main family, and 



