204 



Mixter — Acidic Oxides with Sodvwm Oxide. 



This number multiplied by 23T70, the molecular weight of 

 Ag.O. gives 20,000° for the heat effect of Ag 2 + Na,(). ; . 



Silver oxide. Ag.O, does not exhibit, so far as known, any 

 acidic property towards strong bases or basic oxides. More- 

 over only the higher oxides of metals are as a rule acidic 

 oxides. Hence it is probable that a compound of silver per- 

 oxide, Ag.,( ).,, with one or more molecules of sodium oxide is 

 formed. On this assumption the following are derived from 

 the experimental data : 



2Ag + 2NaO, = Na„O.AgO + Na,0 + 6,000° 



2Na O + 20 = 2Na ,0., + 



38,8()0 C 



2Ag + 20 + Na 2 = Na,O.Ag„0, + 44,800° 



Ag„0 + Na 2 2 = Na 2 O.Ag 2 2 + . __ 20,000°, 



Na 2 + O = Na 2 2 + 19,400° 



Ag a O + O + Na 9 = Na 2 O.Ag 2 2 4- 

 2Ag + = AgO f 



39,400° 

 5,400° 



Considering the unavoidable errors, 5,400° found for the 

 heat of formation of silver oxide agrees fairly with Thomson's 

 result of 5,900°. 



Gold. 



Fernand Meyer"" observed that precipitated gold reacts 

 violently with molten sodium peroxide with formation of sodium 

 aurate. Determinations of the heat effect of the reaction and 

 also that of Ka 2 + Au 2 3 have been made and it has been 

 found that both reactions are attended with very considerable 

 heat. 



Gold powder required for the investigation was prepared by 

 throwing down the metal from a dilute solution by sulphurous 

 acid. The brown precipitate obtained was washed, dried and 

 then rubbed through a sieve having 50 meshes to the inch. 

 The sodium peroxide used was also sifted through the same 

 sieve and the heat of one gram of sulphur burned in the per- 

 oxide was found to be 5276°. The heat effect of the iron wire 

 used for ignition was taken to be 44°. The following are the 

 experiments : 



Gold 



S 



Na 2 2 ] 



Heat observed 



" due to Fe and S 



For 1 gram of gold 



1 



2 



3 



4 





5-000 



5-000 



5-000 



5-000 



grams 



1-000 



1-000 



1-000 



1-000 



a 



14- 



12-4 



13- 



13- 



a 



5650° 



5774° 



5675° 



5725° 





5320° 



5320° 



5320° 



5320° 





330° 



454° 



355° 



405° 





66° 



91° 



71° 



81° 





*C. E. 14.1 



5, 805, 1907 









