206 Mixter — Acidic Oxides with Sodium Oxide. 



metallic gold mixed with the auric oxide used. It should be 

 stated that oxygen was not liberated by the fusions. 



Tlic heal of formation of auric oxide is derived as follows : 



2Au +.}Na a O, = 3Na,O.Au a 3 + 30,400° 



3N a O + 30 = 8Na a O a + 58,200° 



•_'Au + 30 + 3Na 2 = 3Na 2 O.Au a 3 + 88,000° 



and 



Au„0 3 + 3Na,0 = 3Na„O.Au„0 3 4- - 100,900° 



hence 



2Au + 30 = Au,0, — —12,300° 



a 3 



Apparently these results are fair since —12,300° found for 

 the heat of formation of Au.,0 3 agrees well with Thomson's, 

 which is 2 Au + 30 + Aq = Au 2 3 Aq - 13,200°. The exper- 

 iments with gold and auric oxide show conclusively that the 

 heat of formation of sodium aurate is very large. 



The heats of the formation of the peroxides of copper and 

 silver are not known. They are probably negative and small. 

 Assuming the amounts of these heats to be negligible, we 

 have 



Cu a 4 + (Na.O), = 59,000° 



A g,°a + (Na a O) x = 39,000° 



Au a 3 + 3Na 2 = 101,000° 



The peroxide of copper is taken as Cu a 4 so that it may for 

 comparison contain two atoms of metal. In previous papers 

 it has been shown that the heats of combination of acidic 

 oxides with sodium oxide is closely related to the atomic 

 weights of the elements of a sub-group. In the case of the 

 peroxides of copper, silver and gold this relation is lacking. 

 The heat of Ag„0„ + (Na 2 0) x is much less than corresponds to 

 the atomic weight of silver. The explanation appears to be 

 this : Silver is more basic than copper and gold, and its perox- 

 ide contains only one atom of oxygen to one of silver, while 

 the other two oxides contain more than one atom of oxygen to 

 one of copper or gold. 



