On Chemical Tests, 



305 



tic acid is destroyed, and the bases of these salts may be obtained se- 

 parate, or combined only with carbonic acid, and in this state may be 

 recognised by properties which are more characteristic than those be- 

 longing to them in a state of more energetic combination. In this 

 way the alkaline bases may be obtained separately from the earthy 

 ones ; for the addition of water to the incinerated mass takes up the 

 former, and leaves the latter. 



h. Phosphoric and oxalic salts occasion a precipitate also, with bary- 

 tic solutions, which is soluble in dilute muriatic and nitric acids with- 

 out effervescence,, See the last article b. 



41. BISMUTH, the salts of bismuth may be recognized by water pre' 

 cipitating them ; by the precipitate becoming black by sulphuretted 

 hydrogen, and by a black precipitate with hydrosulphuret of ammonia. 

 Before the blow-pipe they fuse easily into a brittle button, which flies to 

 pieces under the hammer ; the charcoal becoming coated with a yellow pow« 

 der. They are distinguished from lead by giving no precipitates with 

 sulphuric acid ; and by the brittleness of the fused globules from the 

 blow-pipe. 



a. Carbonate of baryta perfectly separates the oxide of bismuth in 

 cold solutions from peroxide of copper, and from lead, manganese, and 

 nickel. The carbonates of lime and magnesia also precipitate bismuth 

 whether in hot or cold solutions. See 69, c. 



b. The following tests tend further to discriminate bismuth. 

 Potash % ammonia, carbonate of potash, and carbonate of ammonia— 



produce white precipitates insoluble in an excess of the precipitant. 

 Phosphate of soda, a white precipitate. 



Oxalic acid : no immediate precipitate but after some time a crystal- 

 line precipitate is perceptible. 



Prussiate of potash ; white precipitate insoluble in muriatic acid. 



Red prussiate of potash ; pale yellow precipitate soluble in muriatic 

 acid. 



Hydrosulphuret of ammonia ; liquid sulphuretted hydrogen, and sul- 

 phuretted hydrogen gas in a current, produce a black precipitate ; but if 

 the bismuth be in small quantity a dark brown precipitate. 



Metallic zinc. A black spongy precipitate. 



c. Solutions of the salts of oxide of bismuth redden litmus paper. 



42. BRAZII.WOOI3 PAPER. See litmus 77, which may be used 

 as a substitute. 



