shows a vertical section ; the bed is concave, and isconstructed of sand and clay well consolidated; atits middle a pipe, a, forms a canal for the fused metalto flow out as soon as produced, and which is closedby heavy ashes, b is the f.ir channel in the bridge cl,and c is a door through which the prepared ore isintroduced and the residuary slag abstracted. Thefire is shown at /; e is the grate and cj the chimney.
Fig. 8 is a plan of the furnace, wherein the sameletters indicate the same parts.
Sulphide of antimony is dressed for reduction bymixing it with the proper quantity of iron, or ironscales, and alkaline carbonate: 2 or 3 cwts. of orerequire from eight to ten hours’ heat for reduction ;but the metal obtained in this way is very impure,and is therefore remelted in portions of from 20 to30 lbs. in crucibles. These ase covered over withground charcoal, and heated in a reverberatoryfurnace.
The metal obtained by this process contains con-siderable quantities of iron, sulphur, and frequentlyarsenic, lead, and copper. These bodies deteriorateits quality, even for the arts, and of course it cannotbe employed in medicine while the smallest trace of
Fig. 3.
-g-
arsenic is present. It is therefore imperatively neces-sary to subject the crude antimony to purification. Forthis purpose it is fused with £ part of antiinonioussulphide, and an equal weight of sodium carbonate,in a hessian crucible for one hour. On breaking thecrucible after cooling, the metal is carefully separatedfrom the slag, and submitted to a second fusion with1^ part of the carbonate. Sometimes a third fusionis required; but in this case it is to be performedwith 1 part of the alkaline carbonate. Should therebe lead, it remains in the antimony after the secondfusion, although the other metals may be completelyremoved; and from its great fusibility, slight portionsare retained even after the third operation.
If arsenic be absent, a part of the metallic antimonyis oxidized and remains in the slag; but very little,if any, of the metal is thus acted upon whilst arsenicis present.
It has been found that 100 parts of the crudemetal and G parts of the sulphide yield 94 of pureantimony. It is necessary, when larger quantities ofiron are present, to add proportionally more of thesulphide of antimony; for unless there be sufficientsulphur to combine with the whole of the iron, thearsenic cannot be oxidized.
Wohler recommends deflagration of 10 parts ofthe metal with 12 of saltpetre, and 10 of carbonateof soda; the arsenic is oxidized, and forms potassiumarsenite, and the antimony is at the same time con-verted into potassium antimoniate by this treatment.On boiling the fused mass with water, the arsenicalcompound is dissolved, leaving the antimoniate,which is collected, washed, dried, and reduced in theusual way with charcoal in an earthen pot.
The metal obtained by this means still containscopper and iron.
According to Berzelius , the impurities are re-moved by fusing 2 parts of the metal (finely powdered)with 1 part of the trioxide of antimony; the iron,copper, and arsenic are oxidized, and remain in theslag; in this case the lead, should any be present,is still combined with the antimony. Musprattthinks it better to fuse rather more than 4 parts ofantimony with 1 part of manganese dioxide, and tosubject the regulus so obtained to a second fusionwith one-tenth of its weight of sodium carbonate.
As the stibnite is nearly always found associatedwith seams of silicious and calcareous impurities, apreliminary operation is necessary in order to
l'ig. 4.
Fig. 5.
separate it from its gangue; this process is calledeliquation.
Any difference that exists in the manner of eli-quating crude sulphide of antimony is chiefly in thefurnace employed. In Hungary the ancient method,viz. that of roasting the ore in largo pots or crucibles,is still practised. These pots are furnished with anaperture at their bottom, opening into a smaller one,which is embedded in the ground. A cover is ap-pended to the upper pot, which may be luted downafter the vessel is charged. These pots are placed in acircle with a furnace in the centre, the heat fromwhich passes freely under the bottom and round thebody of each pot.
Figs. 4 and 5 are drawings of this arrangement;the former is a section of the elevation, and the lattera plan, showing the position of the crucibles roundthe fire, aaa denote the pots in which the crudeore is heated, and ccc the smaller pots which receivethe liquid sulphide; cl is the fire-grate. In theelevated section, the relative position of thesecrucibles is comprehensively shown, with their con-necting tubes, b b ; both crucibles and tubes are madeof earthenware.
The furnace employed for the fluxier of the crude