84 PROCEEDINGS OF THE AMERICAN ACADEMY 



arsenio-tungstates a paper by Sprenger * on the phospho-tungstates has 

 appeared. Sprenger has examined, with a single exception, only the 

 compounds of the 24 : 1 series, and has added a number of new salts, 

 which, so far as regards their constitution, fully confirm my own results. 

 The compounds described, belonging to the 24-atom series, are the 

 following : — 



24 W0 3 . PA . 3 H 2 -f 58 aq 



24 W0 3 . PA . 3 BaO + 58 aq 



24 W0 3 . P 2 3 . 2 BaO . H.,0 + 58 aq 



24 WO, . P 2 5 . BaO . 2 H 2 -f 58 aq 



24 W0 3 . P 2 5 • 8 Cu 2 -f 58 aq 



24 W0 3 . P~0 5 . 3 Ag 2 -J- 58 aq 



24 W0 3 . P 2 6 . Ag/i . H 2 + 58 aq. 



Sprenger's formula for the octahedral acid agrees with that which I 

 had given if we consider the acid as tribasic. The other salts which 

 he has described are new, and form a valuable addition to our knowl- 

 edge of this class of compounds. It is well worthy of notice, that in all 

 of his salts, the acid included, the number of atoms of water is the 

 same. The acid with 58 atoms of water of crystallization forms, there- 

 fore, a complete and stable molecular structure in which 2, 4, or 6 atoms 

 of hydrogen are replaceable. I do not recall any other series in which 

 this constancy of crystalline water occurs, at least to the same extent. 

 Sprenger has also obtained a salt of the 22-atom series which is of 

 much interest. This is the barium salt 



22 W0 3 . P 2 5 . 7 BaO + 591 aq, 



and its special interest depends upon the fact, first, that the ratio of the 

 tungstic to the phosphoric oxide is as 22 : 1, and, secondly, that the 

 salt contains seven atoms of fixed base, or, in other words, must be con- 

 sidered as derived from an acid containing at least fourteen atoms of 

 hydroxyl. Sprenger asserts that he has obtained the corresponding 

 acid, and it is to be hoped that he will pursue the subject farther. 

 This barium compound furnishes additional evidence of the independent 

 existence of a series in which the ratio is 22 : 1, and in addition it 

 renders more probable the formula which I have given for Debray's 

 silver salt, 



22 Mo0 3 . P 2 5 . 7 Ag 2 -f 14 aq. 



From these two tolerably well-established cases it would appear that 

 * Journal fiir prakt. Cheruie, xxii. 418. 



