METALLURGICAL COLLECTIONS. 
97 
Plattner’s method of gold extraction by means of chlorine, as 
formerly used at Reichenstein, in Silesia, for the treatment of 
residues of arsenical ores (lolingite) containing about 1J ounces 
of gold to the ton, and about 5 per cent, of arsenic, is illustrated 
in this Case. Chlorination processes are still largely employed 
for gold extraction. Of late years, too, a dilute solution of. 
cyanide of potassium has been very extensively used for 
obtaining gold from the “ tailings ” of the gold mills. 
The preparation of many of the other less common metals, 
and their compounds, such as antimony, bismuth, cadmium, 
aluminium, &c., receives illustration in the Pedestal Case No. 35, 
immediately opposite to the Table Case under description ( see 
p. 56). 
The remaining Table Cases of the metallurgical series stand in 
the three embay ments on the opposite side of the room, to which 
therefore we now cross. 
Lead-Smelting. 
Table Case 17. — The. processes of smelting lead and of 
separating the silver from it were known at a very early 
period. The Book of Job clearly describes the metallurgical and 
mining processes; and in Jeremiah we read, “ the bellows are 
burned, the lead is consumed of the fire ; the founder melteth in 
vain. . . Reprobate silver shall men call them.” This 
passage proves the knowledge of the processes of desilverising 
lead by oxidation, such as, until of late years, has been commonly 
employed. The traces of old Roman lead mines are very exten- 
sive in many parts of Europe, and the discovery of Roman pigs 
of lead by no means uncommon. These were usually stamped 
with the name of the emperor under whose reign the lead had 
been produced. One of these Roman pigs of lead will be found 
in the collection, and two casts from other pigs. The original 
pig was one of fifty found in an old smelting work discovered 
near Orihuela, Valencia, Spain ( see Wall Case 44). 
Metallic lead is obtained either by simply roasting the galena, 
or native sulphide, under proper conditions ; or by roasting the 
ore, and then reducing the oxidised products by means of car • 
bonaceous matters ; or finally by removing the sulphur from 
galena by heating it with metallic iron. The operations of lead 
smelting may be conducted either in reverberatory furnaces, in 
blast-furnaces, or on shallow hearths. 
The process of desilverising lead was formerly effected by 
oxidising the lead, the oxide being from time to time removed 
from the furnace, leaving the silver upon the bed of bone ashes 
prepared to receive it. A vast improvement was effected by 
the late Mr. Hugh Lee Pattinson, who discovered that lead con- 
solidated, or crystallised, at a higher temperature than the alloy 
of lead and silver ; consequently that, if he kept lead containing 
silver in a state of fusion at the lowest temperature at which 
the fluid state could be maintained, solid masses were gradually 
formed, which were found to be almost pure lead Thus 
