Preparation and Distribution.—Ozone exists naturally, in moderate and vari able quantities, in atmospheric air. It is formed during thunder-storms and by silent electrical discharges in the atmos phere. It is evolved during the process of evaporation of water, especially of salt water, and also a result of the respiration of plants, especially those belonging to the Coniferm. It is therefore found in Nature at the sea-shore; in forests, espe cially in the pine-woods; at the summits of mountains and of high towers. On the other hand, it is usually absent in crowded cities and where organic matter is undergoing slow oxidation, except after a thunder-storm. A great amount of ozone is formed in the mist rising from the cold ground, under a clear sky, on a calm autumn or winter day. Atmos pheric ozone, according to Schtinbein, is only generated in any considerable quan tity when oxygen, moisture, and sun beams combine, as exemplified and util ized in the bleaching of linens upon the lawn. According to the same authority, under the influence of light the green foliage of plants exhale both ozone and neutral oxygen, both of which are again taken up in part by the growing cells of the plant.
Ozone may be prepared artificially by oxidizing phosphorus in moist air; by the electrolytic decomposition of water; by the slow oxidation of ether, oil of tur pentine, and other essential oils; and by the action of strong sulphuric acid upon a mixture of potassium permanganate and oxalic acid; and also, as shown by A. Houzeau, by the action of strong sul phuric acid upon barium dioxide; and by subjecting a current of oxygen to the action of the static electrical current.
Although the production of ozone by means of static electricity was discovered in 1839, it was not until 1854 that ozone was obtained in any appreciable quanti ties by von Siemens. Andrews and Tait discovered that the silent electrical dis charge between very fine points would yield the maximum of ozone; and that the intermittent discharge, accompanied by the emission of sparks, caused a con siderable amount of ozone produced to be reconverted into ordinary oxygen as fast as it was formed. Von Siemens's apparatus consisted of a sort of Leyden jar, made by coating the interior of a long tube with tin-foil, and passing over this tube a second wider tube coated with tin-foil on its outer surfaces. Between the two tubes a current of dry oxygen is passed, which becomes electrified by in duction, on connecting the inner and outer coating with the terminal wires of an induction-coil (Ruhmkorff coil) or with a Holtz static machine. By this means it is said that from 10 to 15 per cent. of the oxygen may be converted into ozone. Von Siemens and Halske have since improved the original apparatus in many ways.
Houzeau's apparatus consists of a glass tube containing within a stout platinum filament, and wrapped on the outside with a spiral of copper wire or other good conducting material. One of the rheo phores of the induction-coil is connected with the platinum wire, the other with the copper spiral. A current of dry oxy gen-gas is allowed to pass through the tube.
The quantity of ozone produced is in creased by lowering the temperature, about 50 per cent. of the oxygen being converted into ozone at —SS° F. Based upon this principle, W. J. Morton devised an effective machine which is much im proved in detail (N. Y. Med. Jour., June 23, 30, '94), the output of the machine being measured in milligrammes of ozone per minute, and the dosage regulated ac cordingly.
Tests for Ozone.—In the presence of potassium iodide and moisture ozone will cause the liberation of free iodine (one third of its volume acting in this libera tion and two-thirds escaping as oxygen). Based upon this, test-papers are prepared by immersing sheets of unsized (bibu lous) paper into a solution of starch and potassium iodide; these sheets are dried and afterward cut into strips of conven ient size. For use one of the strips is moistened and exposed; if ozone be pres ent in the air, it will liberate free iodine, which in turn will act upon the starch, producing a blue color (iodide of starch).
Bibulous paper dipped into tincture of guaiac will turn blue upon exposure to ozone.
Moistened indigo test-papers are de colorized by ozone.
In applying these tests it should be re membered that most of the reagents re act similarly to hydrogen dioxide and to ozone, and allowances should be made therefor.
Physiological Action.—The air con tains about two parts of ozone in one million: a quantity thought sufficient to act as a stimulant to the respiratory tract. To the absence of ozone in the air has been attributed many ailments, espe cially neuroses such as hay fever and the "nervousness" of which women most fre quently complain. The fact that such disorders seem to be improved after a thunder-storm has apparently sanctioned this view and led to the use of ozone as a remedy. In concentrated form it causes, when inhaled, inflammation of the respiratory tract and coagulation of the blood in the superficial arteries, though it restores the fluidity of the blood outside of the body. The local effect is attributed to its destructive fluence upon the epithelium of the re spiratory tract and inhibition of its func tions, besides interference with the dis charge of carbon dioxide. The toxic ef fects thus brought about unfavorably affect general metabolism and cause de pression of cardiac action.