88 Mr. Hatchett's Experiments on the various Alloys , 
of the former metals is sufficient to destroy the ductility of gold. 
It may therefore be suspected, that the brittle quality which 
certain kinds of copper communicate to gold, proceeds from 
those metals ; for, although other metallic substances produce 
the same effect, yet, as the former especially are so commonly 
present with the ores of copper, it is highly probable that anti- 
mony, or lead, may remain combined with the smelted copper, 
in a proportion too small to affect the general and more obvious 
properties of that metal, yet still sufficient to destroy the ducti- 
lity of gold, when such copper is employed as an alloy. 
To ascertain how far copper might be alloyed with lead, or 
antimony, without any very apparent change in its obvious pro- 
perties, the following experiments were made. 
To 47 6 grains of fine malleable copper, in fusion, four grains 
of antimony were added, and, being well mixed, the whole was 
poured into a mould. 
The colour of this copper, when filed and polished, was such 
as not easily to be distinguished from that which had not been 
thus alloyed. 
It was also hammered and rolled, without shewing any signs 
of brittleness. The specific gravity was 8,354.* 
The like quantity of copper was alloyed with four grains of lead. 
This also was ductile, and did not suffer any apparent change 
of colour. 
The specific gravity was 8,472. 
The same experiment was repeated with four grains of bis- 
muth ; but the copper thus alloyed was exceedingly' spongy and 
brittle. 
* The finest Swedish copper was employed in these experiments j the specific 
gravity of it was 8,895, 
