powdered coal, 30 per cent of crude antimony, and 20 per cent of carbonate of potash), is added to the metal and smelted. The mass is then ladled into moulds in such a manner that the ingots are covered with slag not more than of an inch high. This slag separates on cooling, and the metal surface shows a star if the metal does not contain more than 4 per cent of impurities. The resulting regulus is broken, re-smelted with an addition of crude antimony, and refined; the mass is descorified and mixed with some star slag.

2. By Oxidation by Means of Saltpetre, and by Reduction. An admixture of 8 parts of crude antimony, 6 parts of raw tartar, and 3 parts of saltpetre are charged into a redhot crucible and smelted; the saltpetre forms antimoniate of antimony, which is then reduced by the tartar. This expensive mode yields only 43 per cent.

3. By Smelting with Iron and Fluxes.-This method gives a larger yield, but the antimony is ferruginous, and requires calcination. The smelting is conducted in crucibles, in air furnaces, or in small reverberatory furnaces. The decomposition is effected best by spongy iron, which, however, gives rise to the formation of a too ferruginous metal.

A high temperature, causing the volatilisation of a great deal of antimony, is required for smelting, owing to the small difference between the specific gravity of sulphide of iron and antimony, and because sulphide of iron is more difficult to fuse. The volatilisation is prevented by the addition of fluxes (sulphide of sodium, sulphate of soda, and carbon); these combine with the sulphide of iron, forming thin, easily fusible slags, which completely separate from antimony at a moderate red heat. An excess of sulphide of sodium scorifies sulphide of antimony.

Berthier states that pure SbS, yields from 65 to 70 per cent of antimony, when 100 parts are smelted together with 60 parts of iron scale, from 45 to 50 parts of carbonate of soda, and 10 parts of pulverised coal.

KARST. Arch., 1 R., iv., 261; viii., 285; xi., 39; xiii., 380.

The following method, adopted by Liebig* and Bensch†, is less expensive, and yields antimony free from arsenic :100 parts of sulphide of antimony are smelted together with 42 parts of iron filings, 10 parts of dehydrated sulphate of soda, and from 2 to 3 parts of carbon; 16 parts of the resulting regulus are kept in a fused state for an hour, mixed with 2 per cent of sulphide of iron, I part of sulphide of antimony, and 2 parts of soda. The regulus is again smelted with I parts of carbonate of soda, and again with I part of soda, till the slag takes a light yellow colour. The extraction of arsenic seems to be effected by the sulphide of iron; probably a combination is formed similar to arsenical pyrites.

This method is also suitable for purifying the regulus produced by methods 1 and 2; 16 parts of impure antimony yield 15 parts of antimony free from copper, arsenic, iron, lead, or sulphur.

Karsten directs that the ores should be dressed, but not liquated, and then smelted in a reverberatory furnace with a hollow hearth; 2 or 3 cwts. are charged, with 35 or 36 per cent of wrought iron, sulphate of soda, carbonate and chloride of potassium, and coal. After smelting for eight or ten hours, the antimony is tapped off, still being covered with slag. This antimony is re-melted in crucibles containing about 20 or 30 lbs., some carbonate and chloride of potash and coal dust being added.

At Magurka from 18 to 20 lbs. of crude antimony are melted in plumbago crucibles with proper fluxes, and the resulting regulus re-melted in the same manner.

Production of Regulus of Antimony direct from Ores. This method has of late been occasionally adopted for working richer ores. According to the richness of the ores the smelting is conducted either in crucibles, or in cupola or reverberatory furnaces, and the sulphide of antimony is decomposed either by iron (London), or by roasting reduction processes (Septèmes, Bouc).

*

ERDM. Journ. f. pr. Ch., ix., 164; xliii., 78. Dingl., Bd. 63, p. 446. + Dingl., Bd. 107, p. 214.

KARST. Met., iv., 544.

|| Oester. Ztschr., 1856, p. 59.

Only very rich ores are smelted in crucibles; these require not so much to be fire-resisting as of such quality as will prevent antimony passing through at lower temperatures.

At the lead works at Enthoven, near London (Rotherhithe), antimonial ores containing from 50 to 55 per cent of antimony are smelted in pieces the size of an egg, in crucibles which are manufactured of fire clay, plumbago, and pieces of old crucibles. The ores are put into crucibles heated to a moderate red heat, and a quantity of alkaline slag is charged upon them, and 20 lbs. of old scrap iron placed on the top; the mass is gradually fused, the pieces of iron are pressed into it, and after 1 or 2 hours, when completely fused, are poured into conical iron moulds. The crucibles are then re-charged; when cold the contents of the moulds are easily separated into raw antimony and sulphide of iron; the raw antimony is afterwards refined; 10 or II cwts. of ore are smelted in twelve hours.

The smelting of antimonial ores is adopted at Septèmes and Bouc, near Marseilles. The ores treated are sulphide of antimony and senarmontite from Constantina, containing 60 per cent of antimony, and red antimony from Corsica and Tuscany, containing from 45 to 55 per cent.

The sulphuretted ores are roasted; the richer and purer ores are afterwards smelted in reverberatory furnaces, and the poor and impure ores treated in cupola furnaces. The roasting is performed with charges of 5 or 6 cwts., in small reverberatory furnaces with an oval hearth and two grates, one on each of the long sides. The furnace is charged and closed, and then moderately heated for two hours; the roasting mass is turned and raked, and roasted for about six hours till no more sulphurous acid is developed. The roasting mass loses from 12 to 15 per cent in weight, including 1 or 2 per cent of antimony. It is now smelted in furnaces like those represented by Figs. 169 and 170. The hearth is formed of sand and clay solidly beaten together, and slopes down to the middle, where it is provided with the orifice (a), which is closed by dense coal ashes; b is the air channel through the

* B. u. h. Ztg., 1863, p. 328.

bridge; c the door for introducing the prepared ores and running off the slags; d the bridge; e the grate; f the fire or fuel door; g the chimney.

The roasting mass is charged in quantities of 360, 400, or 500 lbs., and mixed with 80 or 100 lbs. of fluxes, consisting of chloride of sodium, carbonate of soda, and sulphate of soda, (the two latter in smaller quantities, and sometimes even the sulphate of soda is omitted), 60 or 70 lbs. of small charcoal, and 200 or 300 lbs. of slag of the previous charge. This is first charged and smelted for about one hour, when the other components are gradually added, 40 lbs. every 15 minutes; the mass is continually stirred on the hearth, the resulting froth is skimmed off, and a stronger fire is given towards the end of the process. Metal and slags are then tapped off into an outside basin, from which they are removed when cool. The separated metal is broken into pieces in the order of its calcination. The process is finished in four or six hours, consuming 5 or 6 cwts. of coal, and yielding 42 or 43 per cent of metal instead of 50 per cent. Part of the lost antimony is, however, regained from the smoke, which is condensed in a channel about 350 feet long. The smoke contains as much as 50 per cent of antimony. The common salt strongly attacks the walls and sole of the furnace, probably on account of the formation of volatile chloride of aluminium.

Cupola furnaces yield more than reverberatory furnaces, and the smelting cost is less, but only when treating poor ores which are less amenable to treatment in reverberatory furnaces. At Sèptemes and Bouc poorer ores containing from 30 to 40 per cent of antimony are roasted in a reverberatory furnace ; I ton of ore consuming in six hours 4 cwts. of coal, with a loss of 12 per cent, including 2 per cent of antimony. From

2 to 2 tons of roasted ore are smelted in 24 hours at a consumption of from 1 to 1 tons of coke, in cupola furnaces with three tuyeres, 3°3 metres high from the tuyeres to the furnace mouth, o'8 to o'g metre deep, and o'6 metre wide; the furnaces are constructed like channel furnaces with closed eye. The resulting metal, containing from 92 to 95 per cent of antimony, is refined.

III. PURIFICATION OF RAW ANTIMONY.

This purification is effected by melting the raw antimony, containing copper, arsenic, lead, iron, and sulphur, with oxidising reagents (saltpetre or antimonic oxide), and with purifying reagents (carbonates of potash and soda), in order to oxidise and scorify the foreign metals; or these metals (iron, arsenic, lead, copper) are sulphuretted by a small addition of sulphide of antimony, or Glauber's salts and coal, and are transformed into sulphides, when they combine with the slag. An addition of chloride of sodium transforms these metals into chlorides, and as such they either volatilise or become scorified. Antimonic oxide decomposes sulphide of antimony thus:

3(SbO3, SbO5) + 4SbS, = 10Sb+12SO2.

The carbonate of soda reacting as a flux also decomposes sulphide of arsenic, forming carbonic acid, arsenious acid, and sulphide of sodium. Sulphide of sodium fluxes with FeS, CuS, and AsS,, whilst the arsenious acid combines with soda. A repeated smelting with soda is required for a complete removal of arsenic, which is facilitated by the presence of a small amount of iron, as a combination similar to arsenical pyrites is formed. Sulphide of iron must be added if the raw antimony does not contain iron. The purifying smelting is effected in crucibles, in reverberatory furnaces, or in air furnaces. In order to furnish the ingots with the starlike appearance on their surface necessary for commerce, the metal must be allowed to solidify under a cover or star slag, and all movement of the moulds must be avoided.

At the Enthoven lead works, near London, the raw metal is sorted according to the amount of iron it contains, which