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.
Several oxides of osmium are known. The protoxide, OsO, is obtained as a dark grey insoluble powder when osmium sulphite is heated with sodium carbonate in a current of carbon dioxide. The sesquioxide, Os2O3, results on heating osmium with an excess of the tetroxide. The dioxide, OsO2, is formed when potassium osmichloride is heated with sodium carbonate in a current of carbon dioxide, or by electrolysis of a solution of the tetroxide in the presence of alkali. It is insoluble in acids and exists in several hydrated forms. The osmiates, corresponding to the unknown trioxide OsO3, are red or green coloured salts; the solutions are only stable in the presence of excess of caustic alkali; on boiling an aqueous solution of the potassium salt it decomposes readily, forming a black precipitate of osmic acid, H2OsO4. Potassium osmiate, K2OsO42H2O, formed when an alkaline solution of the tetroxide is decomposed by alcohol, or by potassium nitrite, crystallizes in red octahedra. It is stable in dry air, but in moist air rapidly decomposes. The tetroxide, OsO4, is formed when osmium compounds are heated in air, or with aqua regia, or fused with caustic alkali and nitre. It is obtained as a yellowish coloured mass and can be sublimed in the form of needles which melt at 40° C. It possesses an unpleasant smell and its vapour is extremely poisonous. It dissolves slowly in water, and the aqueous solution is reduced by most metals with precipitation of osmium. It acts as an oxidizing agent, liberating iodine from potassium iodide, converting alcohol into acetaldehyde, &c.
Osmium dichloride, OsCl2, is obtained as a dark coloured powder when the metal is heated in a current of chlorine. Its solution in water is deep blue in colour, but the colour changes rapidly to green and yellow. The trichloride, OsCl3, is only known in solution and is formed by the reducing action of mercury on ammoniacal solutions of the tetroxide. A hydrated form of composition OsCl3.3H2O has been described. The tetrachloride, OsCl4, is obtained as a dark red sublimate (mixed with the dichloride) when osmium is heated in dry chlorine. It is soluble in water, but the dilute solution readily decomposes on standing. It combines with the chlorides of the alkali metals to form characteristic double salts of the type OsCl4.2MCl (osmichlorides). Potassium osmichloride, K2OsCl6, is formed when a mixture of osmium and potassium chloride is heated in a current of chlorine, or on adding potassium chloride and alcohol to a solution of the tetroxide in hydrochloric acid. It crystallizes in dark red octahedra which are almost insoluble in cold water. The aqueous solution decomposes rapidly on boiling. Iodine has no action on osmium, but on warming the tetroxide with a mixture of potassium iodide and hydrochloric acid a deep emerald green, colour is produced, due to the formation of a compound OsI2.2HI; this reaction is a delicate test for osmium (E. Pinerua Alvarez, Comptes rendus, 1905, 140, p. 1254). Osmium disulphide, OsS2, is obtained as a dark brown precipitate, insoluble in water, by passing sulphuretted hydrogen into a solution of an osmichloride. The tetrasulphide, OsS4, is similarly prepared when sulphuretted hydrogen is passed into acid solutions of the tetroxide. It is a brownish black solid, insoluble in solutions of the alkaline sulphides. The atomic, weight of the metal has been determined by K. Seubert (Ber., 1888, 21, p. 1839) from the analysis of potassium and ammonium osmichlorides, the values obtained being approximately 191.
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.
