50 Mr. Hatchett's Experiments on the various Alloys , 
and the gradual cooling of the vessels, in every way promote 
the union of the two metals. 
ADDITIONAL EXPERIMENTS UPON GOLD AND ARSENIC. 
Since the above experiments were written, I was induced to 
examine what effects would be produced by arsenic, in the state 
of vapour, upon red-hot plates of standard gold, the alloy of 
which was copper. 
With the assistance of Mr. Bingley, I therefore made the 
following experiments. 
Two six-inch crucibles were ground so as to fit close when 
the mouth of one was inverted upon the other. Within the 
upper crucible or dome, a plate of the standard gold, which was 
inches long, lj- broad, and thick, and slightly bent, 
was suspended by a strong iron wire ; and one ounce of metallic 
arsenic was put into the lower crucible. The vessels were then 
closely luted, and were placed in an open fire, so that they 
became of a full red heat; they were kept in this state about 12 
or 15 minutes, after which, they were removed from the fire, 
and when cold were opened. 
I then found, that although the heat had been so very much 
inferior to that which is requisite to cause the fusion of gold, 
yet, in the present case, some very extraordinary effects had 
been produced ; for the arsenic, which had been resolved into 
vapour, had acted upon the red hot plate of gold, and had com- 
bined with every part of its surface ; but the combination so 
formed, being extremely fusible, had immediately separated 
from the remaining plate of metal, and had fallen into the lower 
crucible, where it had formed an ingot or button. This ingot 
