OXIDES OF SILVER. GG'J 



from a solution in an acid, by hydrogen and precipitated in 

 the metallic state. This metal is also precipitated by mercury 

 and all the more oxidable metals. Its salts are reduced at the 

 usual temperature by sulphate of iron, of which the protoxide 

 is converted into peroxide. But if the persulphate of iron be 

 boiled upon the precipitated silver, the latter is dissolved again, 

 and oxide of silver and protoxide of iron reproduced. Silver, 

 however, is oxidated when fused or heated strongly in contact 

 with substances for which oxide of silver has a great affinity, 

 as with a siliceous glass, and stains the glass yellow. It is 

 oxidated by concentrated sulphuric acid, with the escape of 

 sulphurous acid. Silver is readily dissolved by nitric acid, with 

 a gentle heat, and with much violence, at a high temperature, 

 nitrate of silver is formed and nitric oxide escapes. Silver 

 combines in three proportions with oxygen forming a suboxide, 

 Ag 2 O, protoxide AgO and peroxide AgO 2 . 



Suboxide of silver, Ag 2 O. The existence of this oxide has 

 only very recently been established beyond doubt by M. Woh- 

 ler. The pure protoxide of silver is completely reduced to the 

 state of metal by hydrogen gas, at 212; but the oxide con- 

 tained in citrate of silver loses only half its oxygen in the same 

 circumstances, the suboxide being formed and remaining in 

 combination with one half of the citric acid of the former salt. 

 The solution in water of the suboxide salt is dark brown, and 

 the suboxide is precipitated black from it by potash. When 

 the solution of the subsalt is heated, it becomes colourless, and 

 metallic silver appears in it. , The salt dissolves of a brown co- 

 lour in ammonia. Several other salts of silver, containing or- 

 ganic acids, comport themselves in the same way as the citrate, 

 when heated in hydrogen.* 



Protoxide of silver, AgO, 1451.6 or 116.3. It is thrown 

 down when potash or lime-water is added to a solution of ni- 

 trate of silver, as a brown powder, which becomes of a darker 

 colour when dried. The powder was found to be anhydrous by 

 Gay-Lussac and Thenard ; its density is 7.H3, according to He- 

 rapath. Oxide of silver is a powerful base, and forms salts, se- 

 veral of which have been found isomorphous with the corres- 

 ponding salts of soda. It is soluble, like oxide of lead, to a 

 small extent in pure water, free from saline matter, and the solu- 

 tion has an alkaline reaction. Oxide of silver is not dissolved 



* Liehig's Annalen, vol. 30, p. 1, 1839. 



