specific Gravity , and comparative Wear of Gold. 59 
As soon as the gold was in complete fusion, about four ounces 
of zinc were put into the large crucible. 
A considerable flame, accompanied by a large quantity of 
white oxide of zinc, immediately arose, and part of the oxide 
adhered to the interior of the large crucible. 
Within half an hour, the crucible containing the gold was 
removed, and was suffered to cool. 
Upon examining the button, it appeared, that a portion of the 
volatilized zinc was combined with the gold ; for the surface 
was dull, and of a Spanish snuff colour ; moreover, it proved to 
be very brittle, similar to the former results. 
From these experiments, it is evident, that zinc is highly in- 
jurious to the ductility of gold; that a portion of it is easily 
separated from gold by heat ; that, when a large quantity of gold 
is alloyed with the standard proportion of zinc, only part of the 
latter is speedily volatilized, but, when small quantities are 
treated, the whole of the zinc becomes separated, and the gold 
remains pure ; that, if zinc is previously combined with copper 
in the state of brass, it is not so easily separated by heat, when 
added to melted gold ; and, lastly, that gold in fusion absorbs 
and retains a portion of zinc, when exposed to the latter metal 
in a volatilized state, even in open vessels. 
GOLD ALLOYED WITH COBALT. 
Experiment 1. 
The effects produced by cobalt upon gold, do not appear to 
have been hitherto investigated ; for this reason, the following 
experiments were made. 
To eighteen pennyweights and ten grains of gold, 23 car. 
3jgrs. fine, when in fusion, one pennyweight and fourteen 
Is 
