ANTIMONIC ACID. G41 



Antimonious acid, Sb O 4 , is obtained by oxidating metallic 

 antimony by nitric acid, or by roasting the sulphuret of anti- 

 mony. It is the state of oxidation into which both oxide of 

 antimony and antimonic acid pass, when ignited in open air. 

 Antimonious acid is infusible and fixed, and is reduced to the 

 metallic state with much greater difficulty than oxide of anti- 

 mony. Fused with potash and separated afterwards from the 

 alkali by an acid, it is obtained as a hydrate, containing 1 eq. 

 of water, and having an acid reaction, SbO 4 + HO. It may 

 also be viewed as a compound of antimonic acid with oxide of 

 antimony. 



When hydrated antimonious acid is digested in hydrochloric 

 acid, a solution is obtained which is supposed to contain a cor- 

 responding chloride of antimony Sb C1 4 . A corresponding sul- 

 phuret of antimony has also been formed. 



Antimonic acid, Sb O 5 , is most easily prepared by the 

 oxidation of oxide of antimony, by nitric acid, as arsenic acid is 

 prepared from arsenious acid. The excess of nitric acid should 

 then be expelled by a heat short of redness. Antimonic acid is 

 a pale yellow powder, tasteless and insoluble in water. It dis- 

 places carbonic acid from the alkaline carbonates, and combines 

 with the alkali. It is also soluble in a boiling solution of po- 

 tash, from which acids precipitate hydrated antimonic acid as a 

 white powder. In the hydrated state antimonic acid is soluble 

 in hydrochloric acid, and also in solutions of the alkalies, with- 

 out heat. Antimoniate of soda is uncrystallizable. Antimo- 

 niate of potash is prepared by deflagrating a mixture of 1 part 

 of antimony, or of sulphuret of antimony, and 6 parts of nitre. 

 The mass is first digested in cold water, which dissolves out 

 nitrate and nitrite of potash, and leaves antimoniate of potash. 

 When this residue is digested in boiling water, a binantimoniate 

 of potash is left, and the neutral antimoniate dissolved out. 

 The solution is feebly alkaline ; when concentrated to the consis- 

 tence of honey, it gives crystalline grains. All acids, even the 

 carbonic, occasion a precipitate in this solution, which is the 

 binantimoniate of potash, KO, Sb 2 O 10 . When a soluble salt 

 of lime or of zinc is treated, at the boiling point, with the solu- 

 tion of the neutral antimoniate of potash, the antimoniate of 

 lime or of zinc separates in a crystalline state ; other salts of 

 antimonic acid fall as an insoluble powder, when solutions of the 

 different metallic oxides are precipitated by the neutral salt. 



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