LEA D COPPER BISM mi. 327 



4. Add solution of potassium ferrocyanide : a reddish-brown pre- 

 cipitate of cupric ferrocyanide, Cu 2 Fe(CN) 6 , is obtained. (Plate III., 5.) 



This is a very delicate test, and should also be made on a highly 

 diluted solution made as directed in test 3. 



5. Add solution of sodium or potassium carbonate : green cupric 

 carbonate with hydroxide is precipitated. (Plate III., 4.) 



6. Immerse a piece of iron or zinc, showing a bright surface, in an 

 acidified solution of copper : the latter is precipitated upon the iron, an 

 equivalent amount of iron passing into solution. (See page 319.) 



CuS0 4 + Fe FeS0 4 + Cu. 



7. Most compounds of copper color the flame green, cupric chloride, 

 blue. The cupric chloride flame can be made very striking by dis- 

 solving the copper salt in a little concentrated hydrochloric acid, 

 pouring this solution on the corner of a piece of iron wire gauze, and 

 holding it in the Bunsen flame. 



8. Cupric compounds give a blue, cuprous compounds a red, borax 

 bead. 



Tests 3, 4, 6, and 8 are sufficient to identify copper compounds. The 

 insoluble ones are made soluble by treating with mineral acids. The 

 sulphate, nitrate, chloride, acetate, and ammonio-salts of copper are 

 soluble in water, most of the other compounds are insoluble. The 

 soluble normal salts redden litmus, due to hydrolysis. 



The ionic equations for the tests are of the same form as those given under 

 the tests for calcium. 



Bismuth, Bi iu = 206.9. Found in nature chiefly in the metallic 

 state, disseminated, in veins, through various rocks. The extraction 

 of the metal is a mere mechanical process, the earthy matter contain- 

 ing it being heated in iron cylinders, and the melted bismuth collected 

 in suitable receivers. 



Bismuth is grayish-white, with a pinkish tinge, very brittle, gen- 

 erally showing a distinct crystalline structure. Occasionally it is 

 used in alloys and in the manufacture of a few medicinal prepara- 

 tions. 



Bismuth has the property of expanding while passing from the liquid to the 

 solid state, and of greatly lowering the fusing point of other metals. These 

 properties make it a useful constituent of many alloys. The presence of bis- 

 muth in dental amalgams renders them sticky and adhesive and causes them 

 to require a larger proportion of mercury. 



Bismuth is trivalent, as a rule, as shown in the chloride, BiCl 3 , or 

 oxide, Bi 2 O 3 , but it is also quinquivalent, as shown by the oxide, 



