82 INTEKESTINE CRYSTALLINE ALLOYS. 



there was no further action, a large percentage of the Cu was 

 dissolved out, and a product was obtained a little darker in 

 colour, containing 93,49 Au and 6.51 Cu (No. 9). 



Crystals were also obtained containing all three metals in 

 the proportion: Gold 60.16; silver, 21.21; copper, 18.63 (No. 10). 



These experiments indicate that Au will not combine with 

 Bi if Ag or Cu are present in sufficient quantity. The crystals 

 of Au and Bi are in fine needle-shaped forms, the system of 

 crystallization not deLarmined ; but possibly rhombohedral (the 

 crystalline form of Bi). 



Au, Ag, and Cu crystallize out together from a solution of 

 these metals in Bi ; the mother liquor, if I may use the expres- 

 sion, containing no Ag or Cu unless these metals are present in 

 excess of what is required to form alloys that will resist the 

 action of dilute nitric acid. 



The following experiment was made with the view of 

 determining the solvent action of Bi, melted at a low temperature, 

 on the crystals of alloy of Au and Ag formed by the process that 

 I have described : 



An alloy was made by melting Au and Ag in about their 

 atomic proportions with Bi, and allowing to cool slowly. The 

 alloy was then heated in a small iron ladle until it became liquid, 

 care being taken not to increase the temperature much above the 

 melting-point. The liquid portion was then poured off and the 

 residue of crystals drained until a pasty mass was obtained. The 

 temperature was then slightly increased, and a further quantity 

 of molten Bi poured off. The percentage of each product was as 

 follows: 56 per cent, of the total weight was poured off at the 

 first melting at a low temperature; 19 per cent, after a slightly 

 increased temperature ; the rest, 25 per cent, (the pasty mass), re- 

 treated with dilute nitric acid, gave a crop of good crystals, which 

 were found to contain : G-old, 59.06; silver, 37.21 (No. 11); Cu 

 and Bi (by diff.), 3.73. Treated with strong nitric acid, their 

 composition became: Gold, 68.53; silver, 27.54; copper, 3.93. I 

 found in this experiment that the pasty residue in the ladle 

 contained only about 62 per cent, of the total gold, the remainder 

 being carried off by the liquated Bi. 



