50 PYROMETALLURGT. [ HI, 



treated witli excess of potassa to redissolve oxide of lead, and 

 then with a measured quantity of sulphuret of sodium solu- 

 tion, until all the lead is thrown down as sulphuret. The 

 solution of sulphuret of sodium employed for the copper-test 

 (30 cub. centimetres of which precipitate 1 grm. copper) is 

 diluted with 3 times its volume of water for the lead-test. 

 Tin, antimony, and arsenic have no influence in this reaction, 

 as they are not precipitated by sulphuret of sodium from a 

 strongly alkaline solution. Iron, nickel, and cobalt rarely 

 occur in galena, and zinc is thrown down white after all the 

 lead is precipitated. This test does not show the presence of 

 bismuth, which precipitates with the lead and is estimated 

 with it. 



It may be remarked, that, although iron forms neither a 

 frequent nor large constituent of good galena, yet it is fre- 

 quently present, in quantity, in less pure ores of lead. But 

 still the test may be used. For after solution of the lead in 

 potassa, and decantation of the greater part, the residue may 

 be diluted and j&ltered, leaving iron, nickel, and cobalt on the 



filter.— j: a B. 



4. Tin. — Thus far, mere traces of tin have been found in the 

 United States, but its value in the arts leads us to wish that 

 it may yet be discovered in workable quantities. It is asso- 

 ciated in minute quantity with nearly all the rutile and tungsten 

 found in the United States. — J. C. B. 



Kersten has recently analyzed several kinds of tin ; No. 1 

 from the Altenberg Zwitterstock, and No. 2 Peruvian. 



In No. 1, the portion soluble in acid was tin, iron, and a 

 trace of manganese ; the insoluble, bismuth and copper, with 

 traces of arsenic, tungsten, and antimony. In No. 2, the 



