Page:EB1911 - Volume 20.djvu/464

Rh is famous for its butter—the only butter made in Sardinia—cheese and other pastoral products; cattle are also bred here.

See D. Scano, ''Storia dell' arte in Sardegna dal xi. al xiv. secolo'' (Cagliari-Sassari, 1907), p. 200.

 OZOKERITE, or (Gr., to emit odour, and , wax), mineral wax, a combustible mineral, which may be designated as crude native  (q.v.), found in many localities in varying degrees of purity. Specimens have been obtained from Scotland, Northumberland and Wales, as well as from about thirty different countries. Of these occurrences the ozokerite of the island of Tcheleken, near Baku, and the deposits of Utah, U.S.A., deserve mention, though the last-named have been largely worked out. The sole sources of commercial supply are in Galicia, at Boryslaw, Dzwiniacz and Starunia, though the mineral is found at other points on both flanks of the Carpathians. Ozokerite-deposits are believed to have originated in much the same way as mineral veins, the slow evaporation and oxidation of petroleum having resulted in the deposition of its dissolved paraffin in the fissures and crevices previously occupied by the liquid. As found native, ozokerite varies from a very soft wax to a black mass as hard as gypsum. Its specific gravity ranges from -85 to -95, and its melting point from 58° to 100° C. It is soluble in ether, petroleum, benzene, turpentine, chloroform, carbon bisulphide, &c. Galician ozokerite varies in colour from light yellow to dark brown, and frequently appears green owing to dichroism. It usually melts at 62° C. Chemically, ozokerite consists of a mixture of various hydrocarbons, containing 85.7% by weight of carbon and 14.3% of hydrogen.

The mining of ozokerite was formerly carried on in Galicia by means of hand-labour, but in the modern ozokerite mines owned by the Boryslaw Actien Gesellschaft and the Galizische Kreditbank, the workings of which extend to a depth of 200 metres, and 225 metres respectively, electrical power is employed for hauUng, pumping and ventilating. In these mines there are the usual main shafts and galleries, the ozokerite being reached by levels driven along the strike of the deposit. The wax, as it reaches the surface, varies in purity, and, in new workings especially, only hand-picking is needed to separate the pure material. In other cases much earthy matter is mixed with the material, and then the rock or shale having been eliminated by hand-picking, the " wax-stone " is boiled with water in large coppers, when the pure wax rises to the surface. This is again melted without water, and the impurities are skimmed off, the material being then run into slightly conical cylindrical moulds and thus made into blocks for the market. The crude ozokerite is refined by treatment first with Nordhausen oil of vitriol, and subsequently with charcoal, when the ceresine or cerasin of commerce is obtained. The refined ozokerite or ceresine, which usually has a melting-point of 61° to 78° C, is largely used as an adulterant of beeswax, and is frequently coloured artificially to resemble that product in appearance.

On distillation in a current of superheated steam, ozokerite yields a candle-making material resembling the paraffin obtained from petroleum and shale-oil but of higher melting-point, and therefore of greater value if the candles made from it are to be used in hot climates. There are also obtained in the distillation light oils and a product resembling (q.v.). The residue in the stills consists of a hard, black, waxy substance, which in admixture with india-rubber is employed under the name of okonite as an electrical insulator. From the residue a form of the material known as heel-ball, used to impart a polished surface to the heels and soles of boots, is also manufactured.

According to published statistics, the output of crude ozokerite in Galicia in 1906 and 1907 was as follows:

 OZONE, allotropic oxygen, O3. The first recorded observations of the substance are due to Van Marum (1785), who found that oxygen gas through which a stream of electric sparks had been passed, tarnished mercury and emitted a peculiar smell. In 1840 C. F. Schonbein (Pogg. Ann. 50, p. 616) showed that this substance was also present in the oxygen liberated during the electrolysis of acidulated water, and gave it the name ozone (Gr. ὄζειν, to smell). Ozone mixed with an excess of oxygen is obtained by submitting dry oxygen to the silent electric discharge [at the temperature of liquid air, E. Briner and E. Durand (Comptes rendus, 1907, 145, p. 1272) obtained a 90% yield]; by the action of fluorine on water at 0° C. (H. Moissan, Comptes rendus, 1899, 129, p. 570); by the action of concentrated sulphuric acid or barium peroxide or on other peroxides and salts of peracids (A. v. Baeyer and V. Villiger, Ber. 1901, 34, p. 355); by passing oxygen over some heated metallic oxides, and by distOhng potassium permanganate with concentrated sulphuric acid in vacuo. It is also formed during many processes of slow oxidation. For a description of the various forms of ozonizers used on the large scale see N. Otto, ''Rev. gén. de chemie pure et appliquée'', 1900, ii. p. 405; W. Elworthy, ''Elekt. Zeits.'', 1904, ii. p. i), and H. GuUleminot (Comptes rendus, 1903, 136, p. 1653). Ozone is also produced by the action of cathode and ultra-violet rays on oxygen. These methods of preparation give an ozone diluted with a considerable amount of unaltered oxygen; A. Ladenburg (Ber. 1898, 31, pp. 2508, 2830) succeeded in liquefying ozonized oxygen with liquid air and then by fractional evaporation obtained a hquid containing between 80 and 90% of ozone.

Ozone is a colourless gas which possesses a characteristic smell. When strongly cooled it condenses to an indigo blue liquid which is extremely explosive (see ). In ozonizing oxygen the volume of the gas diminishes, but if the gas be heated to about 300° C, it returns to its original volume and is found to be nothing but oxygen. The same change of ozone into oxygen may be brought about by contact with platinum black and other substances. Ozone is only very slightly soluble in water. It is a most powerful oxidizing agent, which rapidly attacks organic matter (hence in preparing the gas, rubber connexions must not be used, since they are instantly destroyed), bleaches vegetable colouring matters and acts rapidly on most metals. It liberates iodine from solutions of potassium iodide, the reaction in neutral solution proceeding thus: O3+2KI+H2O=O2+I2+2KHO, whilst in acid solution the decomposition takes the following course: 4O3+10HI= 5I2+H2O2+4H2O+3O2 (A. Ladenburg, Ber. 1901, 34, p. 1184). Ozone is decomposed by some metallic oxides, with regeneration of oxygen. It combines with many unsaturated carbon compounds to form ozonides (C. Harries, Ber. 1904, 37, pp. 839 et seq.).

The constitution of ozone has been determined by J. L. Soret (Ann. chim. pays., 1866 [4], 7, p. 113; 186S [4], 13, p. 257), who showed that the diminution in volume when ozone is absorbed from ozonized oxygen by means of oil of turpentine is twice as great as the increase in volume observed when ozone is reconverted into oxygen on heating. This points to the gas possessing the molecular formula O3. Confirmation was obtained by comparing the rate of diffusion of ozone with that of chlorine, which gave 24.8 as the value for the density of ozone, consequently the molecular formula must be O3 (cf. B. C. Brodie, Phil. Trans., 1872, pt. ii. p. 435). More recently A. Ladenburg (Ber. 1901, 34, p. 631) has obtained as a mean value for the molecular weight the number 47.78, which corresponds with the above molecular formula. Ozone is used largely for sterilizing water.