[39] Adie (1889) obtained compounds of As_{2}O_{3} with 1, 2, 4, and 8 SO_{3} by the direct action of ordinary and Nordhausen sulphuric acid upon As_{2}O_{3}. Weber had previously obtained As_{2}O_{3}SO_{3} (which disengages SO_{3} at 225°), and also other As_{2}O_{3}_n_SO_{3} (where _n_ = 3, 6, and 8), by the action of the vapours of SO_{3} upon As_{2}O_{3} at a definite temperature. The compound As_{2}O_{3},8SO_{3} loses SO_{3} at 100°. Oxide of antimony, Sb_{2}O_{3}, gives similar compounds. Adie (1891) also obtained (by the action of SO_{3} upon H_{3}PO_{4}) a compound H_{3}PO_{4}3SO_{3} in the form of a viscous liquid decomposed by water. _Antimony_ (stibium), Sb = 120, is another analogue of phosphorus. In its external appearance and the properties of its compounds it resembles the metals still more closely than arsenic. In fact, antimony has the appearance, lustre, and many of the characteristic properties of the metals. Its oxide, Sb_{2}O_{3}, exhibits the earthy appearance of rust or of lime, and has distinctly basic properties, although it corresponds with nitrous and phosphorous anhydride, and is able, like them, to give saline compounds with bases. At the same time antimony presents, in the majority of its compounds, an entire analogy with phosphorus and arsenic. Its compounds belong to the type SbX_{3} and SbX_{5}. It is found in nature chiefly in the form of sulphide, Sb_{2}S_{3}. This substance sometimes occurs in large masses in mineral veins and is known in mineralogy under the name of antimony glance or _stibnite_, and commercially as _antimony_ (Chapter XX., Note 29). The most abundant deposits of antimony ore occur in Portugal (near Oporto on the Douro). Besides which antimony partially or totally replaces arsenic in some minerals; thus, for example, a compound of antimony sulphide and arsenic sulphide with silver sulphide is found in red silver ore. But in every case antimony is a rather rare metal found in few localities. In Russia it is known to occur in Daghestan in the Caucasus. It is extracted chiefly for the preparation of alloys with lead and tin, which are used for casting printing type.[40] Some of its compounds are also used in medicine, the most important in this respect being antimony pentasulphide, Sb_{2}S_{5} (_sulfur auratum antimonii_), and tartar emetic, which is a double salt derived from tartaric acid and has the composition C_{4}H_{4}K(SbO)O_{6}. Even the native antimony sulphide is used in large quantities as a purgative for horses and dogs. Metallic antimony is extracted from the glance, Sb_{2}S_{2}, by roasting, when the sulphur burns away and the antimony oxidises, forming the oxide Sb_{2}O_{3}, which is then heated with charcoal, and thus reduced to a _metallic state_. The reduction may be carried on in the laboratory on a small scale by fusing the sulphide with iron which takes up the sulphur.[40 bis]