72 PROCEEDINGS OF THE AMERICAN ACADEMY 



corresponding to 



12 WO3 . PA . 3 BaO, and 20 WO3 . F^O, . 6 U^O. 



As regards the mode of replacement, however, our views must de- 

 pend upon the special form of structural formulas which we pro- 

 visionally adopt. With the view which I have taken of the subject, 

 we may write for a phospho-vanadic acid assumed to have the 

 formula 



6VA-P205.3H,0, 



corresponding to the phospho-tungstic acid 



6WO3.PA.3Hp, 



the structural formula, 



I 1 



VIO2 — O — O — VIO2 



I I 



VIO2 — O — — VIO2 



VIO2 — O — O — VIO2 



In the formula of the phospho-vanadic acid assumed, I have repre- 

 sented the complex V2O2 by VI ; and it is easy to see how, structurally, 

 this may be regarded as hexatomic, and as replacing W^^ or Mo^^, 

 since we may reasonably suppose that we have 



O — V = 



I i 



o — v=. 



With this view of the subject ( Vo02)02 = WOo = MoO., etc. This 

 mode of formulating compounds containing vanadic pentoxide enables 

 us, as I have shown, to reduce many complex salts to relatively 

 simpler types, and is supported, as we shall presently see, by the for- 

 mulas of a special class of vanadates exactly corresponding to meta- 



