86 PROCEEDINGS OP THE AMERICAN ACADEMY 



HO-W0 2 = W0 2 -OH 



i " i 



HO-W0 2 — W0 2 -OH 



i I 



HO-W0 2 — W0 3 - OH 



i i 



o 



1 I 



3 (HO) = PO-O-OP = (OH), 



This formula explains the basicity of the acid satisfactorily. It 

 also shows that, as six atoms of hydroxyl are united with phosphorus, 

 and six with tungstic oxide, there should be theoretically a limiting 

 case corresponding to an acid containing six atoms of hydroxyl, and 

 represented by the formula 



6 W0 3 . P 2 5 . 3 H 2 or 6 W0 2 . 3 . P 2 5 . (HO) 6 



and structurally by 



wo 2 = wo, 



i \ 0/ i 

 W0 2 -0- wo 2 



II II 



W0 2 -0- wo 2 



o 



1 I 



3 (HO) = PO - O - OP = (OH), 



According to this view six atoms of hydroxyl are always associated 

 with phosphorus, or, as the case may be, with arsenic. I consider this 

 view of the subject by far the more probable. At the same time, how- 

 ever, it is also possible that we may have the structural formula, 



in which all the atoms of hydroxyl are associated directly with tung- 

 sten, and in the present state of our knowledge we can only decide the 



