OZONE (Gr. ozo, I'smell). It was remarked long ago that a peculiar odor was pro duced by the working of an electrical machine. Van-Martini found that, when electric sparks were passed through a tube containing oxygen, the gas became powerfully impregnated with this odor—which he therefore called the "smell of electriety.” Subsequent writers attributed the phenomenon to the formation of nitric acid due to a trace of nitrogen mixed with the oxygen;" especially as the gas was found to act ener getically upon mercury. Thus supposed to be explained, these curious results were soon forgotten. But in 1840 Schtinbein (q.v.), with remarkable acuteness, made a closer investigation of the question, and arrived at many most curious results, all of which have not even yet been satisfactorily accounted for. The problem remains, in fact, one of the most perplexing, as well as interesting, questions imperfectly resolved in chernig try.
• The earlier results of Sehiinhein were as follows: (1.) When water is decompokd by the voltaic current, the electrodes being of gold or platinum, the oxygen (which appears at the positive pole) possesses in a high degree the smell and the oxidizing power devel oped by Van-Marum by means of friction-electricity., (2.) When the positive electrode is formed of an oxidizable metal, these results are not observed, but the electrode is rapidly oxidized. (3.) The oxygen collected at a platinum electrode retains these pro perties for an indefinite period, if kept in a closed vessel; but loses them by heating, by the contact of an oxidizable substance, and even by contact with such bodies as charcoal and oxide of manganese. To the substance, whatever it may be, which possesses such poWerful chemical affinities, Sehonbein gave the name ozone, from its peculiar smell.
In 1845 he showed that the same substance can be produced by the action of phos phorus on moist air; and suggested that it might be a higher oxide of hydrogen.
De la Rive and Marignae shortly afterwards, repeating the experiments of Marum, showed that electric sparks produce ozone even in pure and dry oxygen; and came to the conclusion that ozone is oxygen in an allotropic state, as diamond is a form of coke or charcoal.
Baumert, in 1853, endeavored to show that there are twig kin& of ozone—one formed from pure oxygen by electric sparks, which he allowed to be allotropic oxygen; the other formed in the voltaic decomposition of water, which he endeavored to prove to he a teroxide of hydrogen But Andrews, in 1856, completely refuted this view, by showing that no such oxide of hydrogen (at least in a gaseous form) is produced in the electrolysis of water; and that ozone, from whatever source obtained, is the same body; and is not a compound, but an allotropic form of oxygen.
In 1860 Andrews and Tait „published the results of a series of volumetric experiments on tins snbject, which led to some remarkable conclusions—among which are the fol lowing: When the electric discharge is passed through pure oxygen, it contracts. If ozone be oxygen in an allotropic form, it must therefore be denser than oxygen. It was
found also that a much greater amount of contraction, and a correspondingly greater quantity of ozone, were produced by a silent discharge of electricity between fine points than by a brilliant series of sparks. The contraction due to the formation of the ozone is entirely removed by the destruction of the ozone by heat; and this process can he repeated indefinitely on the same portion of oxygen.
In attempting to determine the density of ozone, they used various bodies to take up the ozone from the oxygen containing it; and met with many very curious results*. Thus, if mercury be introduced'it is immediately attacked and oxidized, and yet the oxygen increases in volume. If iodine be employed, it is immediately oxidized, and no change of volume was observed, though the apparatus would have at once rendered visible a change to the amount of of the bulk of the oxygen By measuring the contraction produced by electricity in the oxygen, then the effect of introducing a solution of iodide of potassium, and determining the amount of oxygen taken up from the quantity of iodiue set free, Andrews and Tait showed that the density of ozone, if it be allotropic oxygen, must be practically infinite—i.e., that ozone must have the density of a liquid or a solid at least, although existing in the gaseous form. This conclusion is, they say, inevitable, unless we make the very improbable assumption, that when iodine, etc., are exposed to ozone, one portion of the ozone (of volume, as oxygen, c quid to the the volume of the whole ozone) combines with the iodine, and the other portion is res tored to the form of oxygen. The paper from whose statements we have quoted con cludes with the suggestion that it is possible that, in the formation of ozone, oxygen may be decomposed. This is, of course, contrary to all the received notions of chemistry— but such a supposition would at once reconcile all the apparently contradictory facts connected with this singular body. Soret and Von .Babo have recently repeated and verified a few of these results, and the former, by using turpentine as an absorbing sub stance, and also by measuring its diffusion rate, has endeavored to show that the density of ozone is 50 per cent greater than that of oxygen—a result on the whole consistent with the recent experiments of Brodie. Andrews has lately shown that ozone is rapidly d stvoyed when shaken up with dry fragments of glass, etc. Ile has also proved that the effect which is (almost invariably, and sometimes in fine weather powerfully) pro duced by the air on what are called ozone-test papers—papers steeped in iodide of potas sium (and generally spoiled by the addition of starch) which are rendered brown (or blue) by the liberation of iodine—is really due to ozone. Ile did so by showing that it acts upon mercury as ozone does, and that it is destroyed by heat at the same tem perature. This action is more strongly manifested in the air of the open country titan in that of towns; and its absence would seem to imply vitiation of the atmosphere.