USEFUL METALS 133 



Methods of Extraction. Bismuth is obtained in large quan- 

 tities as a l\ -product in the treatment of gold, silver and lead 

 ores. Two methods that are applicable to the treatment of 

 l>iMimth ores may be outlined as follows: 



(1) Roasting. The ore is crushed, and then heated in re- 

 torts. The molten metal drains off through inclined iron pipe-. 

 The crude metal thus collected is dissolved in nitric acid, form- 

 ing the nitrate of bismuth, Bi(NO 3 ) 3 . This product is treated 

 with water and the subnitrate of bismuth is formed according 

 to the equation, 



Bi(NO 8 ) 3 +2H 2 O = BiO, N0 3 ,H 2 O,+2HNO 3 . 



After the precipitate has thoroughly settled the supernatant 

 liquor is drawn off, the precipitate dried, and the oxide, Bi 2 Oj, 

 is formed. This oxide when roasted in large crucibles yields 

 elemental bismuth and carbon monoxide according to the equa- 

 tion, Bi 2 O 3 +3C = 2Bi+3CO. 



(2) Chlorination. The bismuth ore is crushed, pulverized, and 

 placed in a series of wooden vats and leached with chlorine 

 solutions. The disengaged chlorine dissolves the bismuth. 

 The resulting solution is clarified by filtering. It is then con- 

 ducted into water when the bismuth oxychloride, BiOCl, is 

 formed. The bismuth oxychloride thus precipitated may be 

 dried and sold directly or it may be roasted with lime when 

 chloride of lime and elemental bismuth are obtained. There 

 are several other processes for the manufacture of metallic 

 bismuth in foreign countries but owing to the minor importance 

 of the metal they are omitted. 



Uses of Bismuth. Bismuth is used in the treatment of the 

 precious metals for, like lead, it acts as a collecting agent for 

 these metals. Its recovery power is very high for both gold 

 and silver. The most important use of bismuth is in the manu- 

 facture of many alloys which are capable of wide industrial 

 application. Perhaps the most important of these is Wood's 

 fusible metal which melts at 65. The alloy consists of 4 parts 

 of bismuth, 2 parts of lead, 1 part of tin and 1 part of cadmium. 

 The melting-point is far lower than that of any of its constituents. 

 Bismuth melts at 269, lead at 327, tin at 232, and cadmium 

 at 321.7 C. Other alloys are Lippowitz' metal, fusing at 60; 

 Dorocot's metal, fusing at 93; Newton's fusible metal, fusing at 



