52 Mr. Hatchett’s Experiments on the various Alloys , 
loosely stopped with a piece of charcoal, and the crucibles, being 
hrmly luted, were as before placed in an open fire. 
When the vessels appeared of a full red heat, they were taken 
out, and, being placed upon the pavement of the laboratory, 
about half an ounce of metallic arsenic was quickly introduced 
through the aperture that has been mentioned, which was 
again closed, although very imperfectly, by a piece of char- 
coal. The arsenic immediately began to produce flame and 
fumes, which partially escaped through the opening ; in about 
five minutes, the crucibles ceased to appear red-hot, and the 
greater part of the arsenic was dissipated. 
Upon separating the crucibles, the plate of gold was found 
entire, but it was much discoloured ; and the portion of gold 
which had combined with the arsenic, had trickled to the 
edges of the plate, where it became accumulated, and would 
soon have dropped into the lower crucible, had it not been for 
the short duration of the heat. 
The plates of gold which were employed in the two experi- 
ments, had been annealed, and were remarkably ductile ; and it 
has already been observed, that the part of the plate which 
remained after the first experiment, completely retained its 
original ductility; but the plate which had been employed in 
the second experiment, although not brittle, was become less 
flexible. The cause of this difference was very apparent ; for, in 
the first experiment, the whole of the gold combined with 
arsenic had, by the continuance of the heat, been enabled to flow 
from the remaining part of the plate of standard gold, which, 
although thus reduced in size, retained none of the arsenic. 
In the second experiment, on the contrary, the heat ceased, 
