380 



On Chemical Tests. 



[Oct. 



quantity a fine blue colour inclining slightly to violet ; after an hour 

 or two the blue changes to violet or to an amethyst red. A solution 

 of potash produces after adding the ammonia, an apple green preci- 

 pitate. 



Carbonate of potash, apple green precipitate. 



Carbonate of ammonia, apple green precipitate, soluble in excess of 



this test and forming a bluish-green solution. 



Phosphate of soda 7 M7l . . . 



r> • 4 J ~ . i > White precipitate. 

 Jrrussiate of potash S * ^ 



Oxalic acid, after some time a g-eenish precipitate. 



Hydrosulphuret of ammonia, a black precipitate. 



Liquid sulphuretted hydrogen, and sulphuretted hydrogen gas, blacken 

 the solution, and after a very long time a small precipitate appears, but 

 only in neutral solutions. 



a. To distinguish salts of nickel from copper, see 51 a, from cobalt 

 they may be known by their action with ammonia; and by potash on 

 adding it to the ammoniacal solution, as mentioned above. 



b. The soluble salts of nickel are distinguished by a beautiful emer- 

 ald green colour, while the colour of the insoluble salts is usually light 

 green, and in some cases leek green. 



c. To separate nickel from copper and zinc, see'52 ; from bismuth 

 41 a. 



d. A great number of non-volatile organic substances hinder the pre- 

 cipitation of the oxide of nickel by alkalies, but not by hydrosulphuret 

 of ammonia. 



e. Before the blow-pipe salts of nickel produce with borax, or micro- 

 cosmic salt, a reddish coloured bead, which fades on cooling, and the 

 colour often quite disappears when the bead is cold. With soda, on 

 charcoal, they are reduced to a white metallic and magnetic powder* 



90s NITRIC ACID AND NITRATES, detected, see 14. 



91. NITROGEN liberated by nitric acid, see 13 c. 



92. opium detected, see 12. 



93. OSMIUM. The solution of oxide of osmium is best detected by 

 infusion of galls, which presently produces in it a purple colour tha*- 

 soon after changes to a deep vivid blue. With pure ammonia and with 

 lime the solution of osmium changes to yellow, but it is not af- 



