528 Mixter — Thermochemistry and the Periodic Law. 



reverse holds. The only regularity found in the group is in 

 the heat of combination of the pentoxides with sodium oxide. 

 The values are 3Na 2 + P,0 6 = 233 ; 3Na a O + As 2 O s = 203 ; 



Fig. 4. 



300 



250 



200 



Fig. 4. Diagram of Group IV. The heats of formations of the dioxides 

 of silicon, tin and lead are on the heavy line, of the other elements of the 

 group on the light line. 



3Na 3 + Sb 3 6 = 164 Cal. The number 203 is 4 Cal. or 2 per 

 cent higher than the linear value. The results given are the 

 writer's and he considers that new determinations are required 

 to show whether or not the heat effects of the above reactions 



