TIN. 135 



a sulphuret ; it is obtained by roasting the ores, which 

 in the one case drives off the carbonic acid, and in 

 the other dissipates the sulphur ; the roasted ore is 

 then mixed with charcoal and distilled ; the metal is 

 volatile at a very high temperature. 



306. When zinc is strongly heated in the air, it 

 burns with a bright flame, and is converted into a 

 white oxide, which may also be obtained by acting 

 on the metal by an acid ; the metal easily oxidizes 

 and dissolves, forming a salt from which the oxide 

 may be obtained, on the addition of an alkali. Sul- 

 phate of zinc, or white vitriol, is a white salt, very 

 easily soluble in water, and made either from the 

 metal and sulphuric acid, or from the native sul- 

 phuret. 



307. Zinc has a strong affinity for chlorine ; by 

 dissolving the metal in muriatic acid, a solution of 

 the chloride is obtained. It is very soluble in water, 

 and has been much employed to preserve wood and 

 canvas from decay. 



308. Tin occurs native almost entirely as an oxide, 

 from which the metal is obtained pure by merely 

 heating with charcoal. Heated in the air it easily 

 oxidizes, and by the action of acids a protoxide and 

 peroxide may be procured. Peroxide of tin, the same 

 substance which occurs native as tin-stone, is arti- 

 ficially made, as a polishing powder, being called 

 "putty powder." Oxide* of tin has a remarkable 

 affinity for coloring matter, and hence is much used 

 by dyers in fixing colors. The bisulphuret of tin is 



