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 made him commandant of the Imperial Guard, grand-master of the artillery and marshal of the palace. In December 1878 he became war minister, and held the post, with a small break, until 1885. He died at Constantinople, in the palace built for him by the sultan near Yildiz Kiosk, on the 14th of April 1900, and his body was buried with great pomp in the Sultan Muhammad Mosque.

 OSMIUM [symbol Os., atomic weight 190·9 (O＝16)], in chemistry, a metallic element, found in platinum ore in small particles, consisting essentially of an alloy of osmium and iridium and known as osmiridium. It was first obtained in 1803 by Smithson Tennant (Phil. Trans., 1804, 94, p. 411). It may be prepared from osmiridium by fusing the alloy with zinc, the zinc being afterwards removed by distillation. The residue so obtained is then powdered and ignited with barium nitrate, which converts the iridium into its oxide and the osmium into barium osmiate. The barium salt is extracted by water and boiled with nitric acid, when the osmium volatilizes in the form of its tetroxide. As an alternative the osmiridium is fused with zinc, the regulus treated with hydrochloric acid, and then heated with barium nitrate and barium peroxide. After fusion, the mass is finely powdered and treated with cold dilute hydrochloric acid; and when action has finished, nitric and sulphuric acids are added, the precipitated barium sulphate removed, the liquid distilled and the osmium precipitated as sulphide. The sulphide is converted into sodium osmichloride by fusion with salt, in a current of chlorine, the sodium salt transformed into ammonium salt by precipitation with ammonium chloride, and the ammonium salt finally heated strongly (H. Sainte-Claire-Deville and H. J. Debray, An. min., 1859 [5], 16, 74; see also C. E. Claus, Jour. prakt. Chem., 1862, 85, p. 142; F. Wöhler, Pogg. 31, p. 161; E. Leidie and L. Quenessen, Bull. soc. chim., 1903 (8), 29, p. 801). The tetroxide, OsO4, can be easily reduced to the metal by dissolving it in hydrochloric acid and adding zinc, mercury, or an alkaline formate to the liquid, or by passing its vapour, mixed with carbon dioxide and monoxide, through a red-hot porcelain tube. The metal has a blue-grey colour, and may be obtained in the crystalline state by solution in tin. Its specific gravity is 21·3-22·48 (Deville and Debray) and its specific heat is 0·03113 (Regnault). It can be distilled in the electric furnace. In the massive state it is insoluble in all acids, but when freshly precipitated from solutions it dissolves in fuming nitric acid. On fusion with caustic potash it yields potassium osmiate. It combines with fluorine at 100° C, and when heated with chlorine it forms a mixture of chlorides. A colloidal variety was obtained by A. Gutbier and G. Hofmeier (Jour. prakt. Chem., 1905 (2), 71, p. 452) by reducing osmium compounds with hydrazine hydrate in the presence of gum arabic.

 OSNABRÜCK, a town and episcopal see of Germany, in the Prussian province of Hanover, situated on the Hase, 70 m. W. of the city of Hanover, 31 m. by rail N.E. of Münster, and at the junction of the lines Hamburg-Cologne and Berlin-Amsterdam. Pop. (1905) 59,580. The older streets contain many interesting examples of Gothic and Renaissance domestic architecture, while the substantial houses of the modern quarters testify to the present prosperity of the town. The old fortifications have been converted into promenades. The Roman Catholic cathedral, with its three towers, is a spacious building of the 13th century, partly in the Romanesque and partly in the Transitional style; but it is inferior in architectural interest to the Marienkirche, a fine Gothic structure of the 14th and 15th centuries. The town hall, a 15th-century Gothic building, contains portraits of some of the plenipotentiaries engaged in concluding the peace of Westphalia, the negotiations for which were partly carried on here from 1644 to 1648. Other important buildings are the museum, erected in 1888-1889 and containing scientific and historical collections; the episcopal palace and the law courts. The lunatic asylum on the Gertrudenberg occupies the site of an ancient nunnery. The town has an equestrian statue of the emperor William I., a statue of Justus Möser (1720–1794) and a memorial of the war of 1870–1871. Linen was formerly the staple product, but it no longer retains that position. The manufactures include machinery, paper, chemicals, tobacco and cigars, pianos and beer. Other industries are spinning and weaving. The town has large iron and steel works and there are coal mines in the neighbourhood. A brisk trade is carried on in grain and wood, textiles, iron goods and Westphalian hams, while important cattle and horse fairs are held here.

Osnabrück is an ancient place and in 888 received the right to establish a mint, a market and a toll-house. Surrounded with walls towards the close of the 11th century, it maintained an independent attitude towards its nominal ruler, the bishop, and joined the Hanseatic League, reaching the height of its prosperity in the 15th century. The decay inaugurated by the dissensions of the Reformation was accelerated by the ravages of the Thirty Years’ War, but a new period of prosperity began about the middle of the 18th century. The bishopric of Osnabrück was founded by Charlemagne about 800, after he had subdued the Saxons. It embraced the district between the Ems and the Hunte, and was included in the archbishopric of Cologne. By the peace of Westphalia it was decreed that it should be held by a Roman Catholic and a Protestant bishop alternately, and this state of affairs lasted until the secularization of the see in 1803. In 1815 the bishopric was given to Hanover. The last bishop was Frederick, duke of York, a son of the English king George III. Since 1857 Osnabrück has been the seat of a Roman Catholic bishop.