ANTIMONY.— Smelting.
2-13
presents a fine stellated appearance. In consequenceof this crystalline property, the alchemists consideredthe phenomenon symbolical of that mysterious lumi-nary which was to guide them in their occult pathto the discovery of a universal medicine, or thephilosopher’s stone.
At 800° Fahr. the metal fuses, and at a white heatit slowly but distinctly volatilizes in closed vessels;in a current of hydrogen, however, it distils withtolerable facility. If exposed to a stream of oxygenon ignited charcoal it burns brilliantly, evolving awhite light, and is at the same time converted into thetetroxide (Sb a 0 4 ), which is eliminated in the form ofa thick whitish smoke. Should a globule of the metalat a high temperature be dropped from an eminenceupon a board or plate of iron, the mass subdividesinto numerous smaller globules, which hop along theplane in a combustible state, marking the coursethey take by a white streak or line of the tetroxide.
Antimony is not sensibly affected on exposure tothe air at the ordinary temperature; its surfacebecomes slightly tarnished, but does not rust. Ifexposed to the air during fusion, rapid oxidationtakes place.
Hydrochloric acid dissolves antimony with theevolution of hydrogen and the formation of the tri-chloride (SbClj); concentrated sulphuric acid oxidizesit, sulphurous acid being at the same time evolved; butif the acid be diluted with water it does not dissolveit. Nitric acid, even when very dilute, rapidlyattacks antimony, and converts it into a white in-soluble powder which is the trioxide,tetroxide(Sb 2 0 4 ),or the pentoxide (Sb 2 0 6 ), according to the strength ofthe acid and the tune of digestion. Aqua regia con-verts the metal into the trichloride.
The specific gravity of antimony is 6712, and itsspecific heat, according to Kegnault, is (M)5077.
For preparing the metal on a large scale, the tri-sulphide (stibnite, or grey antimony ore, Sb 2 S 8 ) isgenerally employed, as well for the abundant pro-duce which it yields, as on account of its reductionbeing more easily effected than that of any other oreof the metal, with the exception of the native oxide ;the latter, however, is never met with in sufficientquantity, and consequently is seldom used.
There are two varieties of stibnite, the massiveand the fibrous: the former presents a long columnarcomposition, and the latter is distinguished by itsplumous, woolly, or felt-like appearance ; it is of alight lead colour, sometimes dull externally, andoften iridescent.
Fig. l.
The mineral is met within crystals of the rhombic-( prism (Fig. 1), which are( sometimes aggregatedlaterally. Before the blow-
_/ pipe, on charcoal, sulphide
C of antimony fuses and is~~7 absorbed, giving off at
_-/ the same time sulphurous
acid and white fumes of the trioxide of the metal.
The most celebrated localities productive of thismineral arc Felsobanya, Chemnitz , and Crenmitz, in
Hungary , whence the grey antimony is procured;Dumfriesshire in Scotland , where the fibrous andlaminated variety is found; and Cornwall, where themassive sort is raised. Other varieties of the sul-phide are also to be found, at Magurka in Hungary ,at Freyberg and Braunsdorf in Saxony , and at Stol-berg in the Ilartz.
Manufacture of Antimony on tiie Large Scale.—Many of the operations in the preparation ofantimony on the large scale are the same as thosewhich will be mentioned hereafter, when describingthe dry assay of the antimonious compounds. Themethod most commonly followed is, first to converttlie sulphide into oxide, and then to reduce withcream of tartar.
The sulphide of antimony is deprived of its sulphur,and oxygen substituted by heating with free accessof air, as in the annexed equation:—
Antimonious « Antimonious Sulphurous
sulphide. y ° e ' oxide. oxide.
Sb 2 S 3 + 90 = Sb 2 0 3 + 3S0 2
This change is conducted in a reverberatory fur-nace, where the comparatively large amount ofoxygen required to displace the sulphur (which is
Fig. 2.
also oxidized), is derived from the abundant currentof air flowing over the heated mineral. During theroasting the attendant should be mindful of the greatvolatility of trisulphide of antimony, and regulatethe heat so as to prevent the loss of material whichwould attend the application of a too elevated tem-perature. The charge of stibnite must be well stirredwith an iron slicer or rake during the roasting, toinsure every part coming in contact with the atmo-sphere. When properly roasted the mass has agreyish-white appearance.
Having obtained the oxide in the manner described,it is intimately mixed with about a tenth of its weightof cream of tartar, and reduced in large earthen cru-cibles, heated in a wind furnace, when the followingdecomposition takes place:—
Antimonious Potassiumoxide. acid tartrate.
Antimony.
Potassium
carbonate.
Carbonic
oxide.
Water,
Sb 2 0 3 + 2 IvC 4 H 5 0 3 = 2Sb + K 2 C0 3 + 7CO + 5II 2 0