276 PROCEEDINGS OF THE AMERICAN ACADEMY. 



The selenium was determined by reduction with sulphurous acid and 

 the molybdic oxide by difference. In spite of the mode of prepara- 

 tion, the salt did not contain phos^shoric pentoxide. On repeating 

 the preparation of the salt I obtained different results, the pro- 

 portions used being probably not the same. The solution deposited 

 first groups of colorless crystals, and then gave after further evapora- 

 tion a white granular crystalline salt. The grouped crystals seemed 

 at first to be quite insoluble in water, but when boiled dissolved, and 

 then crystallized out very readily. Perhaps more than one salt was 

 formed in this operation. The solution of the salt analyzed gave pale 

 yellow crystalline precipitate with argentic and mercurous nitrates. 



Selenoso- Tungstates. 



When ammonic tungstate is boiled with a solution of SeOgHo it 

 readily dissolves to a pale yellow solution, which almost immediately 

 gives beautiful shimmering scales in a pale yellow mother liquor. 

 These pass at once through a filter and are difficult to separate and 

 wash. Potassic tungstate also readily dissolves in a solution of sele- 

 nious acid, forming a pale yellow solution which on heating suddenly 

 becomes opaque, while a pale yellow precijiitate is thrown down. 

 'When washed by decantation with cold water, both the ammonic and 

 potassic salts have a distinct pale yellow color. When a solution of 

 selenious acid is mixed with one of 12:5 sodic tungstate and a solu- 

 tion of potassic bromide is added, a white precij^itate m very minute 

 granular crystals is formed, settling rather slowly, and very slightly 

 soluble in hot water. A solution of argentic nitrate gave, with the 

 well washed salt, large very pale yellow crystalline flakes. Mercu- 

 rous nitrate gave a pale yellow crystalline precipitate. A solution of 

 selenious acid mixed with one of 24 : 1 : 2 sodic phospho-tungstate 

 gave a white granular precipitate very slightly soluble in hot water. 

 After careful washing, this gave, on boiling with argentic nitrate, a 

 perfectly white crystalline salt, a bright yellow crystalline precipitate 

 with mercurous nitrate, and a white crystalline precipitate with baric 

 chloride. It is possible that phospho-seleuoso-tungstates are formed in 

 this manner. 



Pechard * has recently described salts of two series of molybdo- 

 eelenites, as he terms them, having respectively formulas which 

 would indicate that they are derivatives of the acids ; 



4 ILO . 3 SeOg . 10 M0O3 , and 2 HoO . SeO,, . 5 M0O3. 



* Comptes Rendus, CXVI. 1441-1444; also, CXVII. 104-106. 



