INTERESTING CRYSTALLINE ALLOYS. 88 



The ratios of the gold and silver in these three products 

 were as follow: 



f Approximately.) 



First liquation An 74.16 Ag 25.84 Au3Ag2 



Second liquation, . . . Au 65.35 Ag S4.65 AuAg 

 Pasty residue, . . , . Au 71.33 Ag 28.67 Au4Ag3 



In all these alloys of Au, Ag, and Cu, the only crystalline 

 form observed was that of the regular octahedron without any 

 modifications.* 



Alloys of Bismuth and Platinttm. 



Experiments were made to see how far it was possible to 

 prepare in a similar way crystalline alloys of platinum and 

 bismuth. 



Pt and Bi were melted together and allowed to cool slowly in 

 the usual way. The brittle alloy was treated first with dilute 

 nitric acid and then with strong acid. A black crystalline 

 powder was obtained, which, under the microscope, showed some 

 few crystals, form not determined. 



A second experiment was made with the addition of Cu to a 

 similar mixture as before. A highly crystalline, jet-black residue 

 was obtained, which, on examination, proved to be binoxide of 

 platinum. 



Crystalline alloys are obtained in the saine way as with Au ; 

 but these compounds, unlike those containing Au, are decom- 

 posed by nitric acid ; the metals Bi and Cu that entered into the 

 composition of the alloy being entirely replaced by oxygen, and 

 this without destroying the structure of the crystal, as will be 

 seen by examination (No. 12). The black crystals became red- 

 hot in a current of hydrogen, water being condensed on the 

 sides of the tube, a grayish- white powder of Pt being left be- 

 hind (No. 13). A loss of weight was sustained in this experi- 

 ment equal to 13.75 per cent., which is very near the amount of 

 oxygen required by the formula PtOa- On heating in a tube, 

 it gives off 0, a grayish- white powder of Pt remaining. 



The black crystals can be ground easily in a mortar without 

 showing the slightest evidence of metallic particles. Alcohol is 

 readily oxidized by this compound. On heating the crystals, a 

 trace of reddish-brown gas is given off, probably due to a small 

 quantity of occluded nitric oxide. 



* The Bi used for most of these alloys was somewhat impure, containing nota- 

 bly a little copper. 



