GIBBS. — COMPLEX INORGANIC ACIDS. 275 



The silica was determiued by igniting the salt with free access of 

 air until all the molybdic oxide was exjielled. The reactions of a so- 

 lution of the sodium salt were as follows. No precipitate with baric 

 and calcic chlorides. None at first with potassic bromide, but on 

 standing bright yellow crystals formed. A sulphur yellow crystalline 

 precipitate with mercuric nitrate and a beautiful bright orange-yellow 

 highly crystalline precipitate with mercurous nitrate. A very pale 

 yellow crystalline precipitate with argentic nitrate and a pale yellow 

 line-graiued crystalline precipitate with thallous nitrate. Pechard * 

 has obtained the same salt by precisely the same process as that 

 which I have employed, and has priority in publication. I have 

 also obtained a titanio-molybdate and a zirconio-molybdate by similar 

 methods, but have not analyzed them. Pechard has described beau- 

 tiful salts of the two series, and rendered further work on my part 

 unnecessary. 



Selenoso-Molybdates. 



When 24 : 1 phospho-molybdate of potassium is boiled with a solu- 

 tion of potassic selenite SO.Ka it readily dissolves to a perfectly clear 

 and colorless liquid, which after an hour deposits beautiful large gran- 

 ular colorless crystals in abundance. These are readily soluble in hot 

 water, and crystallize from the solution without change, except that 

 large transparent colorless crusts are obtained. Of this salt, analyzed 

 by Mr. G. W. Patterson : 



1.1360 grams gave 0.1503 gram of selenium = 13.23% = 18.09% SeOa- 

 1.1360 grams gave 0.7772 gram PtCleK, = 13.27% K,0. 

 0.9570 gram lost up to 175° C. 0.0058 gram HoO = 0.61%. 



Deducting the small percentage of water, the analyses correspond to 

 the formula. 



17 MoO, . 6 SeO, . 5 KoO. 



1 



3568 100.00 



The formula may also be written, 



6 {SeOa . 2 M0O3} -f 5 M0O4K0. 



* Comptes Rendus, CXVII. 691-694. Cited in Zeitschift fur anorg Chemie, 

 VI. 200. 



