256 PROCEEDINGS OF THE AMERICAN ACADEMY. 



1.1441 grams lost on gentle heating 0.1583 gram water = 13.84%. 

 0.9383 gram lost on gentle heating 0.1313 gram water ^ 13.99%. 

 1.8069 grams gave 1.4033 grams WO3 + Pt = 77.66%. 

 0.8809 gram gave 0.6847 gram WOg+Pt = 77.72%. 

 * gram gave gram platinum == 2.46% Pt02. 



The analyses agree with the formula, 



30 WO3 . PtO^ . 12 NaaO + 72 aq., 

 which requires : 



9226.5 100.00 



In the analyses the water was determined by heating in an air-bath, 

 and not by ignition. No correction for oxygen of PtOg is therefore 

 applied. The solution of the salt gives the characteristic white scaly 

 crystals with NH4CI and KCl, and as in the last two cases we may 

 safely assume that the compound is a double salt. The most probable 

 formula considering the mode of formation is, 



10 WO3 . PtOa . 4 NasO + 2 {10 WO3 . 4 NagO} + 72 aq. 



From the above it appears that, strictly speaking, none of the com- 

 pounds described correspond to the silico-tungstates of Marignac, all 

 of which appear to contain four molecules of basic oxide. Such plati- 

 num compounds may, however, exist in combination, as seems to be 

 shown in the salts last described. 



The other metals of the platinum group will probably be found to 

 form similar compounds. Want of material has prevented a careful 

 study of the subject, but a number of qualitative tests made with small 

 quantities of salts of iridium, ruthenium, palladium, and osmium ap- 

 peared to show clearly that these metals also form compounds with 

 tungstic and raolybdic oxides analogous to those of platinum. 



8:2:3 Platino-mohjbdate of Ammonium. When freshly prepared 

 sodic platinate NaoO . 3 Pt02 is boiled with a solution of 14 : 6 am- 

 monic molybdate, it readily dissolves to an orange-yellow liquid, which 

 after a time deposits beautiful lemon-yellow crystals, which may be 

 easily purified by recrystallization. The salt dissolves rather easily in 



* The data of this analysis were accidentally lost. 



