272 PROCEEDINGS OP THE AMERICAN ACADEMY 



The analyses correspond very closely to the formula, 



60 WO3 . 3 P2O5 . Y.fl, . VO2 . 18 BaO + 150 aq, 

 which requires : — 



0.76 



13.44 

 20066 100.00 



The baric oxide is estimated by difference. The relation of this 

 salt to the aurora-red octahedral phospho-vanadio-tungstate of barium 

 already described is interesting. We have respectively the formulas, 



60 WO3 . 3 P.O^ . VA . V 0, .18 BaO +150 aq, 

 60 WO3 . 3 pp. . V2O5 . VA . 18 BaO + 144 aq, 



and it is easy to see how, at least theoretically, one salt could be pre- 

 pared from the other. With respect to the rational constitution of the 

 green salt, it is possible at present only to form a provisional hypoth- 

 esis. I am disposed to regard it as a triple compound, and to assign 

 to it the formula, 



3(12 WO3 . F,0, . 3 BaO . 3 H.O} + 1 2 WO3 . Vp, . 5 BaO . H,0 + 



12 WO3 . V02.4BaO 



In this formula all the terms correspond to known compounds, the 

 last to the dodeka-silico-tungstate type established by Marignac, VOg 

 replacing SiO^. Of course, as in similar cases, various other formulas 

 may be proposed. I lay no particular stress upon the view I have 

 taken, which a wider and deeper study of these compounds may prove 

 to be untenable. The formation of the salt may be expressed by the 

 equation, 



3 {20 WO3 . PoO, . 6 BaO} + V.O^ + V0,= 



60 WO3 . 3 P.O^ . V.O^ . TO, . 18 BaO. 



The formula must be doubled to permit of a representation by 

 means of a symmetrical structural formula. If we omit all the 

 molecules of tungstic oxide except two, in order to save space, the 



