328 METALS AND THEIR COMBINATIONS. 



Bi 2 O 5 , corresponding to P 2 O 5 , Sb 2 O 5 , I 2 O 5 , or N 2 O 5 . In fact, bismuth 

 forms, besides the two oxides mentioned, two others of the composition 

 Bi 2 O 2 and Bi 2 O 4 , corresponding to the respective nitrogen oxides. 

 A characteristic property of this metal is decomposition of the con- 

 centrated solution of any of its normal salts by the addition of much 

 water, with the formation and precipitation of so-called oxysalts or 

 subsalts of bismuth, while some bismuth with a large quantity of 

 acid remains in solution. This is due to the very weak basic charac- 

 ter of Bi(OH) 3 . 



The true constitution of these subsalts is as yet doubtful, but a 

 comparison of them has led to the assumption of a radical Bismuthyl, 

 BiO, which behaves like an atom of a univalent metal. 



The relation between the normal or bismuth salts, and the subsalts 

 or bismuthyl salts, will be shown by the composition of the following 

 compounds : 



Bismuth chloride, BiCl 3 . Bismuth yl chloride, (BiO)CL 



" bromide, BiBr 3 . " bromide, (BiO)Br. 



iodide, BiI 3 . ' iodide, (BiO)I. 



" nitrate, Bi(NO 3 ) 3 . " nitrate, (BiO)NO 3 . 



sulphate, Bi 2 (S0 4 ) 3 . " sulphate, (BiO) 2 SO 4 . 



carbonate, Bi 2 (CO 3 ) 3 j carbonate, (BiO) 2 CO 3 . 



not known. ) 



The nature of normal bismuth salts and bismuthyl salts may be 

 explained by saying that the first are derived from the triacid base 

 Bi(OH) 3 , the latter from the monacid base BiO.OH. These two 

 hydroxides are related to one another thus : 



Bi(OH) 3 = Bi/ H + H 2 0. 



Bismuth subnitrate, Bismuthi subnitras, BiONO 3 .H 2 O ? (Oxy- 

 nitrate of bismuth}. By dissolving metallic bismuth in nitric acid, a 

 solution of bismuth nitrate is obtained, nitrogen dioxide escaping : 

 Bi + 4HNO 3 = Bi(NO 3 ) 3 + NO + 2H 2 O. 



Upon evaporation of the solution, colorless crystals of bismuth 

 nitrate, Bi(NO 3 ) 3 5H 2 O, are obtained. 



If, however, the solution (or the dissolved crystals) be poured into 

 a large quantity of water, the salt is decomposed with the formation 

 of bismuthyl nitrate and nitric acid, which latter keeps in solution 

 some bismuth : 



Bi(N(V 3 + 2H 2 = BiON0 3 .H 2 O + 2HNO 3 



Subnitrate of bismuth is a heavy, white, tasteless powder, of a 



