OP ARTS AND SCIENCES. 235 



scribed, or rather of the corresponding acid, may be written, in 

 accordance with the general principles already assumed, as follows : — 



M0O2 = M0O2 



I I 



O O 



I I 



M0O2 = M0O2 



I I 



o o 



I I 



HO - M0O2 — M0O2 - OH 



I I 



HO - M0O2 — M0O2 - OH 



I I 



O O 



I I 



HO - PO OP - OH 



li II 



Hg Hg 



In this formula the acid is supposed to correspond to the ammonium 

 salt described. 



HYPOPHOSPHO-TUNGSTATES. 



The salts of this series are not very well defined as regards their 

 physical properties, and it is difficult to obtain any single one in a state 

 of perfect purity. They are most readily prepared by boiling acid 

 tungstates with a solution of hypophosphorous acid, and appear to be 

 in general very soluble in water, yielding sometimes thick syrupy 

 liquids, and sometimes gelatinous masses more or less colored by the 

 partial reduction of tungstic teroxide. 



Potassic Salt. — When a strong solution of hypophosphorous acid is 

 mixed with one of 12 : 5 acid sodic tungstate, the liquid becomes turbid 

 and yellowish, and after a short time gelatinizes to a pale yellow mass. 

 This is to be dissolved in boiling water, and a solution of potassic 

 bromide added, which after a short time gives a white crystalline pre- 

 cipitate, to be drained upon the filter-pump, redissolved in hot water, 

 again crystallized, drained, washed with cold water, and dried on wool- 

 len paper. As thus prepared, the salt presented small colorless granular 

 crystals, soluble in hot water to a somewhat turbid strongly acid liquid, 

 which effervesced with alkaline carbonates. The solution gave no 

 precipitate with cupric sulphate, and no copper was reduced on boiling 



