A N T I M O N Y : ITS HISTORY, CHEMISTRY, MINERALOGY ...

THE METALLURGY OF ANTIMONY. 115
13 lbs. of wrought iron, but not cast iron. Tinned scrap is preferred ;
and, if it is used, it is beaten up into a round ball, large enough to fit
the top of the crucible. The remaining iron is in the form of turnings
or borings, mixed with the ore together with the salt. The mixture is
dropped into the crucible through a funnel; the furnace hole is then
closed for about half an hour, when the crucible is again examined.
The salt used assists the separation of the slag, and tends to promote
the fusion of the siliceous matters of the ore. On an average four
meltings can be made in each crucible per twelve hours; the richer
the ore is, the shorter is the time required.
The crucibles used are generally 20 inches high and 11 inches
outside across the mouth. They are made of a mixture of good fireclay
and plumbago, which latter must be free from iron. The clay
used has the following compositions:—
Water, H20 .
Silica, SiO2
Alumina, A12O8
Protoxide of iron, i'oO
Lime, CaO
Magnesia, MgO.
Potash, K2O .
Soda, KagO
Titanic acid, TiO8 .
Stourbridge.
7'00
69-00
22*00
1*50
0*49
0'54
0*41
0*18
Hexham.
7*44
59*05
25*61
2*20
0*88
0-75
1-97
0-28
1-53
101-12 99-71
On the whole, the Stourbridge quality is the better of the two.
The crucible, when dry, weighs 42 lbs., of which 35J lbs. are dry
clay, and the remaining 6J lbs. plumbago.
The mould, conical in shape, with a f-inch circular hole at the
bottom, is placed opposite to each crucible. The metal thus obtained
is known as "singles," and contains 91*63 per cent* antimony, 7*23
per cent, iron, 0*82 per cent, sulphur, and 0*32 per cent, insoluble
matter.
The next operation is to purify the " singles " with a small quantity
of liquated sulphide of antimony. The charge for this second process
is : 84 lbs. of singles broken small, 7 to 8 lbs. of liquated sulphide of
antimony, and 4 lbs. of salt. The fusion is closely watched, and
great care must be taken that the metal and the sulphide mix
together thoroughly. The fused mass is stirred now and then
with an iron rod, the time required for a charge being about 1\
hours. When fusion is complete, the slag and matte are ladled off
with an iron spoon, and the contents of the crucible poured into the