Discovery. This remarkable, I might almost say, mysterious principle is probably the most effective of all disinfectants, and, so far as concerns the mere destruction of noxious effluvia, might supersede all others, could it be obtained in sufficient quantity at a moderate cost. Though in some of its effects known long since, its actual discovery may be dated but a few years back. The credit of its discovery is due to Schonbein, of Basle, Switzerland, who published an account of his investigations in 1842, having been led to them by the observation of the peculiar smell produced in the air by electric action; an observation which also gave rise to the name by which ozone is now recognized, derived from the Greek verb o.C<», I smell, or emit odour.

Nature. Singular as it may seem, the nature of ozone has not yet been definitively determined. it was first thought by Schonbein to be identical with peroxide of hydrogen; and this idea is still, or at all events has been until very recently, entertained by some writers. it was, however, abandoned by Schonbein, upon the discovery by Becquerel that electricity, passed through a tube containing perfectly dry oxygen, was capable of developing ozone; and the theory then adopted was, that it was an allotropic condition of oxygen; that is, a condition of oxygen in which, though identical in nature, it has acquired new properties, differing greatly from those exhibited by the gas in its ordinary state. On this basis, Schonbein has recently advanced an hypothesis, beautiful in itself, and happily explaining most, if not all of the phenomena which characterize this remarkable agent. He supposes that oxygen is capable, in its relations to electricity, of assuming three different states; those, namely, of, 1. oxygen in a condition of negative electric polarity, in which it is called ozone; 2. oxygen in a positive electrical state, which he proposes to name antozone; and 3. common oxygen, which is neutral, and consists of the other two united in equivalent proportion. Thus the production of ozone by electrical action is readily explained. When electricity passes rapidly through the air in sparks or flashes, the common oxygen is resolved into the two allotropic forms of ozone and antozone, or negative and positive oxygen, the former of which is recognized by its peculiar odour, and the latter, having no sensible property by which it can be known, nor any striking chemical affinities, escapes notice. But, as the two forms have a strong affinity, they cannot remain long in free contact without combining to form neutral or common oxygen. Hence, the smell of ozone quickly vanishes; the two forms being recom-bined the moment that the decomposing agency is withdrawn. A third set of chemists deny both the identity of ozone with peroxide of hydrogen, and the theory of the allotropic state of oxygen, and maintain that the peculiar powers displayed by the so-called ozone are simply those of oxygen in its nascent state, or that in which, separated from its combinations, it has not yet assumed the gaseous form; a state which has long been known very greatly to increase its oxidizing power. On the whole, the views of Schonbein appear to me to be most consistent with the existing state of knowledge on the subject, and may be received until something more satisfactory shall be developed.

Preparation

A constant production and constant consumption of ozone is going on in the atmosphere; and this agent probably performs an important part in the physical economy of the earth. it is generated during thunder-storms, through the electrical agency of the lightning; and the existence of a violent gust is sometimes recognized, at a great distance from the place of observation, by the extraordinary prevalence of ozone in the air. High winds are thought also to develop it, and it is believed by some to be generated during the evaporation of liquids on the surface of the earth, and the occurrence everywhere of slow oxidation. it has been detected in the oxygen given out by the leaves of plants, and is said to be one of the results of respiration in animals. it is asserted also to be formed during fermentation and the growth of moulds. A certain temperature is necessary to its production; and it ceases to be generated during the greatest heat of summer, and in the coldest weather of winter. in the arctic regions it is not developed, because not wanted to correct atmospheric impurities. A temperature between 50° and 96° F. is said to be compatible with its evolution. it is of course very unequal in the atmosphere at different times and places. in mountainous regions, upon the sea-coast, and in the pure air of the country generally, it prevails more than in large towns, especially in close and filthy places, where it can seldom be detected, being consumed in the oxidation of the organic effluvia. it is thought that, as a general rule, the atmosphere contains normally a certain proportion of ozone, which has been estimated at one in 20,000 parts.

Ozone may be artificially developed from the oxygen of the air in various ways. it is not possible, however, to ozonize at once a large proportion of the atmospheric oxygen. it has been estimated that not more than 1/1300 of any portion of air operated on can be thus changed; possibly because the greater portion of the newly developed principle is neutralized by the antozone produced at the same time. I do not propose even to enumerate the various processes by which this principle is produced; and shall content myself with briefly noticing, in this place, some of the more prominent, reserving for special consideration such as are most convenient for practical purposes, till wo come to the application of the agent as a disinfectant.

The rapid working of an electrical machine ozonizes the air around it, as evinced by the peculiar smell produced. The same result follows the passage of electric sparks successively, or even a continuous stream of galvanism through a confined portion of moistened air, or by a current across a surface of water. Ozone is generated during the galvanic decomposition of water; and in this, and all other cases of electrolysis in which it is produced, is always manifested at the positive pole.