362 METALS AND THEIR COMBINATIONS. 



4. Add sodium hydroxide, ammonium hydroxide, or sodium car- 

 bonate to the antimony chloride solution : in either case white anti- 

 moDOus hydroxide, Sb(OH) 3 , is produced, which is soluble in excess 

 of sodium hydroxide. 



The same reagents added to the solution of tartar emetic produce 

 scarcely any precipitate, due to the solvent effect of the organic (tartaric) 

 acid. 



5. Boil a piece of bright metallic copper in the solution of anti- 

 monous chloride : a black deposit of antimony is formed upon the cop- 

 per. By heating the latter in a narrow test-tube, the antimony is volatil- 

 ized and deposited as a white incrustation of antimonous oxide upon 

 the glass. 



6. Use Gutzeit's or Marsh's test as described under tests for arsenic. 



Tin, Sn = 118.8 (8tannum). This metal is found in nature chiefly 

 as stannic oxide or tin-stone, SnO 2 , from which the metal is easily 

 obtained by heating with coal : 



Sn0 2 + 20 = Sn + 2CO. 



Tin is an almost silver-white, very malleable metal, fusing at the 

 comparatively low temperature of 228 C. (440 F.). It is used in 

 many alloys, and chiefly in the manufacture of tin-plate, which is 

 sheet-iron covered with a thin layer of tin. 



Tin is bivalent in some compounds, quadrivalent in others. These 

 combinations are distinguished as stanuous and stannic compounds. 



Stannous hydroxide, Sn(OH) 2 , is not known. When a solution of 

 sodium hydroxide or carbonate is added to a solution of stannous 

 chloride, a precipitate, H 2 Sn 2 O 3 , is formed, which is derived from 

 Sn(OH) 2 . When it is heated in an atmosphere of carbon dioxide, 

 black stannous oxide, SnO, is formed, which ignites when heated in 

 air, giving stannic oxide. 



Stannic hydroxide (Stannic acid), H 2 SnO 3 , is formed when a solu- 

 tion of stannic chloride is boiled : 



SnCl 4 + 3H 2 = H 2 Sn0 3 + 4HC1. 



It is also formed when sodium hydroxide or carbonate is added to a 

 solution of stannic chloride, or when just enough of an acid is added 

 to a solution of a stannate to effect decomposition : 



Na 2 Sn0 3 + 2HC1 = 2NaCl + H 2 Sn0 3 . 



It is a white substance insoluble in water, but easily soluble in 

 hydrochloric, nitric, or sulphuric acid, forming the corresponding salt, 

 and in caustic alkalies, forming stannates. 



