EXPERIMENTS ON VARIOUS ALLOYS OF GOLD. 287 



SECTION I. 



ON THE VARIOU3 ALLOYS OF GOLD. 



The wear of coin is fubject to be modified by certain phyfical Plan of cxpcri- 

 properties, fuch as ductility and hardnefs, which vary in de- 

 gree, according to the chemical effects produced by different 

 metallic fubftances, when employed in certain proportions as 

 alloys. From thefe confiderations, it appears proper, 



Firft, to examine the effects which the various metals pro- Effects of alloys, 

 duce upon gold, when combined with it in given proportions, 

 beginning with T \f, which is the ftandard proportion of alloy, 

 and in certain cafes gradually decreafing to J of a grain in the 

 ounce of troy, or tj^ part of the mafs. 



Secondly, to examine the fpecific gravity of gold d if- Specific gra- 

 ferently alloyed, and the caufes of certain variations to which vm "" 

 it is liable. 



And, thirdly, to afcertain the effects of friction varioufly Wear. 

 modified. 



GOLD ALLOYED WITH ARSENIC. 



Experiment I. 

 To 5307 grains of gold in fufion, 453 pure arfenic were Gold and 

 added. Only fix grains remained in the ingot, which was ar cmc * 

 brittle. 



Experiment II. 

 To 442 grs. gold were added 19 grs. copper, and on perfect Gold, copper, 

 fufion, 19 grs. pure arfenic, and the whole quickly poured an aremc * 

 out. None of the arfenic remained. 

 Experiment III. 

 480 grains of gold in a fmall crucible was inclofed within Gold and arfe- 

 two larger crucibles, well luted together. 480 grains of pure ™ c ff ^ c,ofe 

 arfenic were included in the outer veffel. Strong and con- 

 tinued heat, (a) raifed fome arfenic in the white oxide, (b) 

 and alfo a final I portion of the gold, (c) and the gold was 

 brittle, with a coarfe gray fracture, an increafe of 1,5 grains 

 in weight, (d) It was difficult to expeli the arfenic by heat. 

 Experiment IV. 

 A plate of gold was fufpended within two crucibles ground Gold expofed to 

 and luted together, pure arfenjc being placed in the lower. Jfenfcat ^rei 



By heat. 



