116 PROCEEDINGS OP THE AMERICAN ACADEMY 



The yellow columnar mass, after re-solution and standing over sul- 

 phuric acid in pleno gave perfectly colorless regular octahedra, which 

 corresponded to the formula, 



24W0 3 . P 2 5 . 6 H 2 + 55 aq, or W 24 P 2 O n (HO) 12 -f- 55 aq. 



In the cases of the two last-mentioned hydrates of the acid, the 

 phosphoric oxide was determined by two successive precipitations as 

 ammonio-magnesic phosphate. The analyses leave no doubt as to the 

 constitution of the acid. Scheibler obtained two different phospho- 

 tungstic acids, to which he gave respectively the provisional formulas 



H 16 PW n O« -[- 18 H 2 0, and H n PW 10 O 88 + 8 H 2 0. 

 I should double these and write 



22 W0 3 . P 2 5 . 6 H 2 -f 45 aq, or W 22 P 2 O e5 (HO) I2 + 45 aq. 



20 W0 3 . P 2 5 . 6 H 2 + 21 aq, or W^P.O^HO)^ -f 21 aq. 

 I have not obtained the acid of the 20-atom series, though I shall 

 show further on that there is at least one well-defined salt in which 

 the ratio of tungstic to phosphoric oxide is as 20 to 1. Scheibler does 

 not give the method which he employed for the separation of the two 

 oxides, and I consider it at least probable that his acid 



22 WO a . P 2 5 . 6 H 2 -f 45 aq 



is identical with the first of the three hydrates which I have described 

 above. 



The solution of phospho-tungstic acid forms a colorless heavy oily 

 liquid, with a high refracting power. It has an acid as well as bitter 

 taste, and readily expels carbonic dioxide from carbonates. On stand- 

 ing for some days, the solution undergoes partial decomposition with 

 deposition of a white crystalline powder. This powder is also almost 

 always deposited, in greater or less quantity, in the preparation of the 



