464 
By the first crystallization, from .0108 per cent. 3 oz. 
lOdwts. 13 grs. per ton Silver, is reduced to .0052 per cent. 
1 oz. 13 dwts. 23 grs. per ton in the crystals; and concen- 
trated to .0140 per cent. 4 oz. 11 dwts. 11 grs. per ton in 
the fluid lead, left in the pot. 
Copper, from 11 oz. 4 dwts. 16 grs. per ton, is reduced to 
4 oz. 19 dwts. 7 grs. in the crystals, and concentrated to 
15 oz. 10 dwts. 23 grs. in the fluid lead. 
In the second crystallization, the separation is still more 
apparent, as a larger proportion of crystals are removed than 
in the first. Ultimately, the Silver is reduced to only 9 dwts. 
3 grs. per ton ; Copper, 1 oz. 15 dwts. 6 grs. per ton in the 
refined lead. 
It will be seen that the amount of foreign metals in the 
crystals should correspond to that in the metal of the next 
pot before crystallizing, and in most cases it is identical in 
others sufficiently near to prove the truth of the analysis. 
Although iron appears in the first crystallization to be 
removed in a similar manner, yet, upon repeating the opera- 
tion, it does not diminish in quantity in the crystals, nor 
become concentrated in the fluid lead, but rather the minimum 
seems to be in the samples of lead taken before crystallization, 
that is immediately after skimming. Contact with the iron 
vessels and ladles then supplies the increased per centage in 
the crystals. 
It is probable that this method of purification succeeds best 
when the amount of impurities is not very considerable. For, 
in the instance of lead containing a large proportion of copper, 
when it is submitted to a regulated temperature just sufficient 
to melt the more fusible metal ; it liquates, leaving a skeleton of 
copper. Upon this, a process is founded, called the liquation 
process, totally different from that described in this paper. 
Thus, by melting at a regulated temperature, by skimming, 
and by crystallization, a lead may be obtained practically 
pure. * 
