OF ARTS AND SCIENCES. 



239 



posed by heating in a porcelain crucible, and fuses at a low red heat, 

 giving off vapors of molybdic teroxide. The fused mass on cooling 

 is bluish gray. It dissolves readily in water to a deep blue liquid, 

 which has a strongly acid reaction, and gives with magnesia-mixture 

 the reaction for phosphoric acid. 



The structural formula of the acid corresponding to the ammonium 

 salt may be written provisionally : — 



MoOj = 

 I 

 



I 

 MoO. = 



'2 

 I 



o 



I 

 MoO-^ 



I 



O 



I 

 M0O2 



I 



o 



I 

 HO — MoO, 



HO — MoO, — 



M0O2 



I 

 O 



I 

 M0O3 



I 



O 



I 



M002 



I 



o 



I 



M002 



I 



o 



I 

 MoO, 



— OH 



MoO„— OH 



If we accept the views now generally received as to the constitution 

 of hypophosphorous and phosphorous acids, the hypophospho-molyb- 

 dates, hypophospho-tungstates, and phosphoroso-molybdates furnish 

 a much needed demonstration of the fact, that in this whole class of 

 compounds part at least of the hydroxyl is united to phosphorus di- 

 rectly, and a part only to tungsten or molybdenum. This will appear 

 at once from the formulas for the two acids, since these cannot be 

 broken up into simpler expressions, 



{Hj . PO . OH}, and {H . PO . (OH)^, 



or from the structural formulas which I have given. I shall return to 



