v 
specific Gravity , and comparative Wear of Gold. 71 
and fourteen grains of copper, so that, at most, there could only 
be \ of a grain of lead in the ounce. 
The colour of this metal resembled the former; and it was 
also very brittle ; but the texture was not spongy, for it was very 
similar to that of gold made standard by copper. 
Experiment vm. 
One ounce of the fine gold, in a small four-inch crucible, was 
placed within another of 12 inches, at the bottom of which, 
about two ounces of lead were put on the outside of the small 
crucible. An inverted crucible, of 1 2 inches, was then luted on, 
and the whole was exposed to a strong heat, in a wind-furnace, 
during two hours. 
When the vessels were cold, and were opened, the colour of 
the gold in the small crucible was found to be unchanged ; but, 
instead of weighing 480 grains, it now weighed 488,1 grs. and 
was so brittle, that it was immediately broken by the hammer. 
As so large a quantity of volatilized lead had thus been com- 
bined with gold, in close vessels, the following experiment was 
made with the free access of air. 
Experiment ix. 
One ounce of fine gold, in a small crucible, was placed within 
another of 12 inches, containing about four ounces of lead, 
which, remaining open, was exposed to a strong heat in a wind- 
furnace, during half an hour. 
The gold in the small crucible was afterwards examined ; and 
the external' colour was found to be but little changed ; the 
ductility of it was also not much injured, for, when repeatedly 
hammered, it only cracked slightly on the edges. 
