64 Mr. Hatchett’s Experime?its on the various Alloys , 
in the manner abovementioned, did not suffer (even when several 
months had elapsed) any perceptible alteration. 
Mr. Bingley, who was always obligingly ready to assist in 
these experiments, at my request, examined the habits of this 
combination of manganese with gold, by the usual process of 
assaying. He found that the manganese was completely me- 
tallized, and combined with the gold, but not in an exactly equal 
proportion throughout the mass ; for, in one part the manga- 
nese amounted to ■§-, and in another to 
The gold defends the manganese, in the metallic state, from 
the action of those acids which usually dissolve it. 
When the mixed metal is exposed to a great heat, with free 
access of air, it loses its metallic lustre, and is covered with a 
dark brown oxide. 
24 carats of the metal, which had been exposed to a consi- 
derable heat under a muffle, acquired of its weight. 
Another time, under similar circumstances, it acquired T r ^ of 
its original weight; but this proportion of oxygen disposed it 
to vitrify, and the mass was fixed to the cupel by a dark blue 
enamel. 
Nitric or sulphuric acid alone, cannot completely dissolve this 
oxide ; but, a little sugar being added to the nitric acid, enables 
it superficially to dissolve the oxide, and to separate it from the 
gold, which then remains clean, and of its natural colour; yet 
the manganese has only thus been removed from the surface, 
for, when the mass is cut, the interior exhibits the original gray 
colour of the mixed metal. 
The gold may be purified from the manganese by lead alone, 
if there is heat and lead sufficient; but this may be more com- 
pletely and certainly performed, by the mixture of silver, and 
separation by nitric acid. 
