1852.) OF THE ROYAL INSTITUTION. 207 
obviously be desirable, when practicable, to obtain it by roasting with 
access of air on auriferous iron pyrites, such as the Californian.— 
The result of several experiments on the smelting of auriferous 
quartz were placed before the audience. The gold is separated 
from the lead by well known and ancient processes of cupellation. 
In the smelting of what is termed ‘‘ Sweep,” or the dust obtained 
by the sweeping of the shops of silversmiths and jewellers, the 
same principle is adopted* Lead is added, either in the metallic 
state, or in a state of combination, from which it may be evolved in 
the metallic state in the furnace, as in the case with certain lead slags. 
The part which mercury plays at the ordinary temperature in the 
amalgamation mills is performed by lead at a high temperature in 
the furnace. Anossow, a Russian engineer, is reported to have 
made successful experiments in the smelting of the gold-sand of 
the Ural by substituting cast iron for lead, and subsequently dis- 
solving out the iron from the gold by sulphuric acid. He asserts 
that by this means he procured a very much larger quantity of 
gold than could have been separated by the most careful washing. 
His results, however, have not been received as correct. The 
results of experiments on the use of cast iron as a vehicle to collect 
the gold, were placed before the audience. By simply melting 
the cast iron in contact with lead, the greater part, if not the 
whole of the gold, appeared to be extracted from the iron with 
which it had been alloyed. 
Although no positive opinion was expressed respecting the 
desirableness, or otherwise, of smelting the auriferous quartz of 
California, yet it was suggested, that in the event of the smelting 
process being adopted, it would, probably, for various reasons be 
found advantageous to smelt the quartz in conjunction with 
some of the South American silver ores, many of which contain 
old. 
e The smelting of auriferous pyrites was next described. The pyrites 
is first roasted, by which process oxide of iron is formed. The 
roasted ore is smelted in a blast furnace with unroasted ore. A 
slag is obtained, and below sulphide of iron (or, as it is termed, a 
*‘ matte,’) containing the gold from the two portions of ore. This 
‘matte’? may be roasted, and again smelted with another portion 
of unroasted ore. A slag and ‘‘ matte” are again obtained, and 
the latter will contain the gold from the three portions of ore. 
The gold may thus be concentrated, and ultimately extracted from 
the “matte” by smelting with lead. Many details were neces- 
sarily given which do not appear in this general notice of the 
lecture. 
The treatment of certain auriferous ores by Chlorine.-— Chlorine dis- 
solved in water has been employed in extracting gold from a poor 
auriferous arsenical pyrites at Riechenstein. ‘The ore is roasted, and 
the products treated with chlorine water. The gold is dissolved as 
chloride, and precipitated from its solution by sulphuretted hydrogen. 
