ANTIMONY. 359 



450 C. (842 F.), and may at a higher temperature be distilled without 

 change, provided air is excluded ; heated in air it burns brilliantly. 



Antimony is used in a number of important alloys, for instance, in 

 type-metal, an alloy of lead, tin, and antimony. 



The best solvent for antimony is hydrochloric acid, containing a 

 little nitric acid, whereby antimonous or antimonic chloride is 

 formed. Nitric acid converts it into antimonous or antimonic oxide, 

 which are almost insoluble in the liquid. 



Three oxides of antimony are known, namely, trioxide, Sb 2 O 3 , 

 pentoxide, Sb 2 O 5 , and tetroxide, Sb 2 O 4 . Antimony differs from 

 arsenic in that the trioxide is more basic than acidic, forming salts 

 with mineral and organic acids. The salts with mineral acids, how- 

 ever, are decomposed by water, and require the presence of free acid 

 for solution. Antimony pentoxide is exclusively acidic in character, 

 forming met-antimonates and pyro-antimonates with caustic alkalies. 

 The tetroxide is neither basic nor acidic. It is formed when either 

 of the other oxides is heated in air to a dull redness for a long time. 



The compounds of antimony commonly met with are the chloride, 

 sulphide, and double tartrate (tartar emetic). 



Antimony trisulphide, Sb 2 S 3 (Antimonous sulphide). The above- 

 mentioned native sulphide, the black antimony, is found generally 

 associated with other ores or minerals, from which it is freed by heat- 

 ing the masses, when the antimony sulphide fuses and is made to run 

 off into suitable vessels for cooling. Thus obtained it forms steel- 

 gray masses of a metallic lustre, and a striated, crystalline fracture, 

 forming a grayish-black, lustreless powder, which is insoluble in 

 water, but soluble in hydrochloric acid with liberation of hydrogen 

 sulphide. 



Antimonous sulphide found in nature is crystallized and steel-gray 

 (Plate V., 6), but it may be obtained also in an amorphous condition 

 as an orange-red (Plate V., 5) powder by passing hydrogen sulphide 

 through an antimouous solution. By heating the orange-red sul- 

 phide, it is converted into the black variety. 



The sulphides and oxides of antimony, like those of arsenic, combine with 

 many metallic sulphides or oxides to form sulpho-salts or oxy-salts. Thus the 

 sodium sulph-antimonite, Na 3 SbS 3 , and the sodium antimonite, NaSb0 2 , are 

 formed when antimonous sulphide is boiled with sodium hydroxide. 



Sb 2 S 3 + 4NaOII = Na 3 SbS 3 + NaSbO, + 2H 2 O. 



By the addition of sulphuric acid, both salts are decomposed, sodium sulphate 

 is formed, and antimonous sulphide is precipitated : 



Na 3 SbS 3 + NaSbO 2 + 2H 2 SO 4 = Sb 2 S 3 + 2Na 2 SO 4 + 2H 2 O. 



