specific Gravity , and comparative Wear of Gold . 117 
“ furnace for about a quarter of an hour, and then suffered to 
“ cool, was broken ; the gold was then found in one lump at 
“ the bottom, and the silver above it, in two pieces, with some 
“ grains enveloped in the salts, which had not been intirely 
“ melted. The silver was perfectly pure, and without the least 
“ mixture of gold; but the gold retained about one-sixth part 
“ of silver." 
He repeated the experiment, with different mixtures of the 
two metals, and found the silver to be always free from 
gold, but that the gold retained a little of the silver, except in 
two instances, in which this was also pure. Mr. Homberg ob- 
serves, that “ unless the gold and silver are nearly in equal 
“ quantities, the separation does not succeed ; and that the only 
“ nicety in the process consists in hitting the due point of fusion ; 
<c for, if the fire is too long continued, or the mixt made to flow 
“ thin, the two metals, after they have parted from one another, 
“ mingle again together.” Lewis’s Phil. Comm, of Arts, p, 86 . 
From these experiments it appears, that the equal distribution 
and mixture of two metals, such as gold and silver, is by no 
means very easy to be made, without certain precautions ; and 
also, that when they have been completely mixed, if they are 
kept in fusion under certain circumstances, a separation, more 
or less perfect, sometimes takes place. This separation appears to 
be according to the relative affinities and specific gravities of 
the two metals, and is the soonest effected when the metals 
have not been perfectly mixed.* 
Soon alter the commencement of the experiments at the Mint, 
* Some compound metals may perhaps be mere mechanical mixtures ; but I am 
inclined to believe, th&t by much the greatest number are true chemical combinations ; 
and consequently, when these last have been properly formed, a separation of the com. 
ponent metals, by the means abovementioned, can seldom if ever be effected. 
