Mixter — Formation of Trisodium OrtAophosphate, etc. Hi 



slowly at room temperature and rapidly in hot water, retaining, 

 however, considerable peroxide. 



In the figure^ atomic weights are plotted as abscissas and 

 heats of combinations as ordinates, The line I shows the heat 

 of the reaction 3Na 2 0, K 2 5 ; II of K 2 , 5 , and III of R„ 3 . 



We observe that, as the atomic weight of arsenic is nearly 

 the mean of the atomic weights of phosphorus and antimony, 

 so the heat of combination of arsenic pentoxide with sodium 

 oxide is almost the mean of that of the union of phosphorus 

 pentoxide and antimony pentoxide. The heat effect of 3Na 2 0, 

 R 2 5 is, therefore, closely related to the atomic weights of 

 phosphorus, arsenic and antimony, and not to the affinity of 

 these elements for oxygen. We also observe that the heat of 

 oxidation of arsenic trioxide is nearly the same as that of anti- 

 mony trioxide to the pentoxide. 



