Mixter — Thermochemistry and the Periodic Law. 533 



atomic weights. This property appears in the following small 

 groups in the even series : 



Potassium, rubidium and caesium of group I 

 Calcium, strontium and barium " " II 



Chromium, molybdenum and tungsten 

 in the combination of their acid 

 anhydrides with sodium oxide, " " IV 



In the odd series we have linear values for 



Phosphorus, arsenic and antimony of group V 

 Sulphur, selenium and tellurium " " VI 



in the combination of their acid anhydrides with sodium oxide. 



Chlorine, bromine and iodine of group VII 



combining with hydrogen and metals. 



The six subgroups where the heats of combination vary with 

 considerable regularity fall in five of the large groups of the 

 Periodic System. New investigations are needed to determine 

 whether the values are strictly linear or not. It is improbable, 

 however, that anv wide variation from linear will be found. 





Table VI. 











2Na + 



2Cu + 



Cu 



+ 



2Ag + 





101 



41 



37 



[54-6] 



6 Cal. 



Differences 





13 6 



17-6 









Mg + O 



Zn + O 







Cd + O 





144 



85 [103] 







57 Cal.* 



Difference 





18 











Mg + S 



Zn + S 







Cd + S 





79 



41* [ 59] 







24 Cal.* 



Difference 





18 











2P + 50 



2 As + 50 







2Sb + 50 





370 



219 [300] 







230 Cal. 



Difference 





81 









u 



for 1 atom of oxygen 



16 











S + 30 



Se + 30 







Te + 30 





103 



42 [ 93] 







84 



Difference 





51 









u 



for 1 atom of oxygen 



17 











KC1 + 30 



KBr + 30 







KI + 30 





— 9-8 



— 11-3 [ 16] 







44 Cal. 



Difference 





27 









a 



for 1 atom of oxygen 



9 











MgO + S0 3 



ZnO + S0 3 







CdO + S0 3 





55 



42 [ 58] 







62 



Difference 





16 









'This Jouraal, xxxvi, 55, and Zeitschr. anorgan. Chem., Ixxxiii, 97, 1913. 



