102 SILVER. 



by any continuance of heat: it is oxidized by 

 common and galvanic electricity. 



It is not oxidized by the air ; but it is tarnished 

 by exposure, because the sulphurous vapours form 

 with the metal a sulphuret of silver. 



Oxide of silver is of a dark olive colour, and is 

 obtained by precipitating it from the nitrate of 

 silver by lime-water, this metal being soluble in 

 the nitric acid. 



Nitric acid can dissolve more than half its weight 

 of silver, the solution depositing crystals. When 

 these are fused by a gentle heat, they may be 

 poured into moulds, and form the substance called 

 lunar caustic, used in surgery. 



Nitrate of silver is used by chemists as a test for 

 muriatic acid; for if it be dropped into any 

 liquid containing muriatic acid, a white precipi- 

 tate will appear, owing to the superior affinity of 

 silver to muriatic acid, and to the insolubility of 

 muriate of silver. Nitrate of silver is very caustic, 

 staining animal and vegetable substances of a 

 black colour, and hence it is employed as a per- 

 manent marking ink for linen, and also for staining 

 hair ; though for this last purpose it should be used 

 with great caution, and much diluted. 



If a few drops of the nitrate of silver be put 

 upon a piece of glass, and a copper wire be placed 

 in it, a beautiful metallic precipitation of the silver 

 will appear in an arborescent form. 



When silver is precipitated from its solution in 

 nitric acid by ammonia, it forms fulminating silver, 

 which is a dangerous preparation ; for it explodes 

 by the slight contact of a body. 



When mercury is added to the nitric solution of 

 silver, a precipitation of metallic silver is formed 



