118 PROCEEDINGS OF THE AMERICAN ACADEMY 



Calc'd. Found. 



14MoO, 2016 49.86 50.02 



4044 100.00 



I give this formula with much reserve, and only as probably cor- 

 rect. To express the presence of hexametaphosphoric oxide, it may 

 be written 



14 MoO,3 . {Ba. . 6 PO^} . BaO + 00 aq. 

 I shall return to the subject at another time. 



STANNO-PHOSPHO-TUNGSTATES. 



The vanadico-vanadio-tungstates and vanadico-vanadio-molybdates 

 which I have described furnish instances of compounds embraced 

 under the general formulas 



m RO3 . 71 R'Oo . p W.O, . r W'.p. 



I shall show that the compounds belonging to this type are very 

 numerous, and frequently very well defined. For the present, it will 

 be sufficient to cite two new series of hitherto undescribed salts, my 

 object being to direct the attention of other chemists to a new field of 

 investigation, and to point out methods of preparation and of analysis 

 which may facilitate their work. 



Stanno-phospho-tungstates are formed when the stanno-chlorides of 

 ammonium or of the alkaline metals are mixed in solution with acid 

 alkaline tungstates. They are colorless crystalline salts, so far as 

 studied. As a representative of this series we may take the am- 

 monium salt. 



Anahjtical Methods. — In these salts the three higher oxides may be 

 determined together by precipitation with mercurous nitrate and mer- 

 curic oxide, but the ignited oxides should be evaporated once or twice 

 with nitric acid to oxidize any reduced tin. Tin may be separated as 

 metal by fusion with potassic cyanide, and phosphoric oxide may be 

 determined after separating tin with sulphydric acid. 



22 : 2 : 1 : 2 Ammomo Stanno-phospho-tungstate. — "When a solution 

 of stanno-chloride of ammonium is poured into a clear cold solution of 



