m - 
90 Mr. Hatchett’s Experiments on the various Alloys , 
Allowing, therefore, that other metallic substances may at 
times be present in copper, and may contribute to affect gold 
which is alloyed with it, yet, for the reasons above related, I am 
inclined to attribute, most frequently, this effect to antimony 
or lead.* 
* Copper which is pure, is uniform in its effects, and does not injure the ductility 
of gold ; it would therefore be proper, in all cases when copper is to be purchased for 
*the purpose of alloying gold, to make a previous trial of it on a small quantity, as this 
would answer every purpose of a tedious and expensive analysis. 
Since the above was written, I have made various experiments in the humid way, on 
the, different kinds of copper which are known in commerce, especially on the 
following : 
No. 1. Finest granulated Swedish copper - - sp. grav. 8,895. 
2. — — Swedish dollar copper - sp. grav. 8,799. 
3. - — — sheet British copper - - sp. grav. 8,785. 
4. Fine granulated British copper - - - sp. grav. 8,607. 
480 grains of the first, only afforded a few particles of sulphate of lead, which could 
not be estimated. 
The second contained both lead and antimony, of which the lead was in the largest 
proportion, as it amounted to nearly one grain of metallic lead, whilst the antimony 
did not exceed half a grain. 
The sheet British copper yielded some lead, with scarcely any antimony ; and, on the 
contrary, the granulated British copper contained antimony with but very little lead. 
We may therefore conclude, that the varieties of copper known in commerce, are 
seldom, if ever, absolutely free from lead or antimony ; and that the brittle quality, so 
frequently communicated to gold by an alloy of copper, arises from the presence of 
one or both of these metals, which, even in the proportion of part of the mass, 
I have already proved to be capable of destroying the ductility of gold. 
I have lately made some farther inquiries concerning the varieties of Swedish 
copper, and am informed, that the fine granulated copper is made in this country 
from the Swedish cake-copper, merely by the ordinary process of granulation ; and, as 
the quality even of this copper has been found variable, the Deputy Master of the Mint 
has of late employed British copper, which has been refined expressly for the pur- 
pose, and seems to answer perfectly well. Respecting the variable and occasional very 
bad quality of the copper dollars, Mr. Swedenstierna, a learned Swedish gentleman 
