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two negative, and in antozone a negative to lie between two positive atoms. It will be at once seen that this hypothesis involves the simultaneous production of a corresponding amount of antozone whenever ozoue is formed. Schonbein, moreover, considered that oue or other of the' bodies is formed whenever oxygen enters into combination with any substance whatever, and he accordingly classed all compounds containing oxygen under two heads; viz. ozonides, or those which contain the negative variety of oxygen, of which the typical representatives are permanganic and chromic acids and the peroxides of manganese, silver, lead, cobalt, nickel, bismuth and iron, all of which he believed to liberate chlorine from its compounds and to turn guaiacum paper blue; and antozonides, or those which contain oxygen in the positive state, typified by peroxide of hydrogen and the peroxides of the alkalies and alkaline earths, which do not exhibit either of the last-named reactions.

Applying the results of his investigations to physiology, Schonbein maintained that the blood-corpuscles resolved the oxygen of the air into its oppositely polarized constituents ozone and antozone; adding that the former was consumed in various oxidizing processes within the body, and that the latter was in part transformed by the bloodcorpuscles into ozone, and the remainder iuto peroxide of hydrogen by combining with the water of the blood. This transformation of antozone into ozone by the action of the blood he supported by showing that tincture of guaiacum is only coloured blue by peroxide of hydrogen (i. e. by antozone water according to Schonbein's hypothesis), when blood- or pus-corpuscles are present. However, it must be remembered that many other substances besides ozone impart a blue colour to guaiacum. Schonbein further maintained, in support of the existence of antozone as a distinct body from ozone, that the former could be produced by rubbing a piece of Bavarian fluor spar, which, according to him, produced a different odour from that of ozone; but in this he seems to have been mistaken, since Schrotter, on the contrary, not only pronounced the odours identical, but further showed that the product thns obtained liberates iodine from iodide of potassium.

In support of the views of Schonbein, Meissner, in 1863, showed that if a stream of electrified oxygen be passed through water, a cloud or mist will appear in the receiver into which it is conducted, the production of which he attributed to the influence of a substance which he named "atmizone," and which was afterwards shown to be identical with Schonbein's antozone. He succeeded in isolating this by passing a stream of electrified oxygen through a solution of iodide of potassium which absorbs all the ozone, while the emerging gas produced a dense white mist after being led through a vessel containing water. By these discoveries Meissner sought to explain the formation of clouds in the atmosphere, regarding these bodies as an aggregate of antozone or " atmizone " aqueous vapour. To the influence of atmizone he also attributed the formation of coal-smoke and tobacco-smoke, as well as the fumes of phosphorus and gunpowder.

Those who maintained the existence of antozone as a distinct body from ozone were of opinion that the former is destitute of the power of oxidizing such bodies as phosphorus and pyrogallic acid, or of liberating iodine from iodide of potassium, while it is readily soluble in water, which it converts into peroxide of hydrogen. Ozone has diametrically opposite properties. Babo and Weltzien, however, and subsequently Nasse and Engler, observing that "atmizone" or antozone is only produced when ozone suffers decomposition from the action of water, and that ozone and autozone are not formed simultaneously when dry oxygen is subjected to the action of electricity, as must necessarily be the case on Schonbein's hypothesis of their constitution, came to the conclusion that the doctrine of the existence of any distinct substance as antozone is erroneous, and that the phenomena of which it is the supposed cause are due to the diffusion of peroxide of hydrogen through air or oxygen, thus completely overturning Schonbein's ingenious hypothesis. Brodie coincides in this view. In support of it Nasse and Engler showed (1) that when a current of electrified oxygen is passed through a tube containing dry zinc-sodium (which absorbs ozone, but has no action at all upon the so-called antozone) and then passed through water, no mist or vapour is produced, thus demonstrating that ozone and antozone are not simultaneously formed; (2) that when a stream of electrified oxygen is conducted through a tube containing chloride of calcium (which absorbs antozone but does not affect ozone), and then passed through water, clouds still appear in the receiver, which could not be the case if their existence depended on the presence of antozone; (3) that all the tests of the so-called antozone are identical with those of peroxide of hydrogen. Even Meissner has recently qualified the assent he formerly gave to Schonbein's hypothesis, which, although it has still a few supporters, is daily losing ground; and it may now be considered as at least provisionally established that the antozone of Schonbein, the atmizone of Meissner, and the peroxide of hydrogen of Thenard are identical. Babo, indeed, is of opinion that the cloud-forming power depends on the presence of nitrogen, but this appears to have been sufficiently refuted by Meissner himself.

Dismissing Schonbein's antozone from our consideration, it is now necessary that we should inquire into the volumetric relations of ozone and oxygen, the modes of preparing the former body, the circumstances which modify its production, and its distinctive properties; and also endeavour to substitute some valid theory of its constitution, since Schonbein's ingenious hypothesis seems no longer tenable.

Ozone may be prepared in at least seven different ways: (1.) By passing electric sparks through air or oxygen, or by the inductive influence of a series of sparks passed along the outer surface of the tube containing the gas. This latter is the preferable modification of the method we are now considering, because the passage of the actual spark destroys a large portion of the ozone as soon as it is formed. Sparks an inch long generate twice as much ozone as those of one sixth of an inch. It is a curious fact that the form and covering of the containing tube exert an immense influence on the amount of ozone produced by this method. Thus, the production of ozone in a row of parallel uncovered tubes is nil; when these are coated and fastened together with a thin covering of wax the quantity produced is appreciable ; it is increased when lateral glass wings are affixed to the tube, still further augmented when sealing-wax supports are added to the glass wings, and reaches its maximum when the tubes are provided with thick glass wings with sharp angular edges. When the angles of these wings are rounded off the production of ozone falls to nil, but it is again formed in abundance on the angles being restored. These facts, however strange, seem to be perfectly well established by Meissner's experiments.

(2.) Ozone may be prepared by the electrolysis of acidulated water, when it appears at the negative pole.

(3.) By placing a piece of phosphorus half covered with tepid water in a vessel of air. The phosphorus ought-to be removed after two hours at latest, as it then begins to absorb a portion of the ozone it had previously formed.

(4.) By the action of strong sulphuric acid upon permanganate of potash, a method judiciously recommended by Dr. Fox when the formation of this body is desired for the purification of the atmosphere in hospitals and theatres. (5.) By dispersing water in a pulverized form through the air, as the electricity generated by the vaporisation of the water dust converts a portion of the atmospheric oxygen into ozone.

(6.) By the introduction of a heated glass rod into a mixture of air and ether-vapour.

(7.) By exposing almost any ether or essential oil to the action of light and air. Dr. Day, of Geelong, recommends that ethers thus ozonized should be employed to disinfect the clothes, bedding, bandages, &c., of the sick in hospitals. A convenient method of producing ozone in hospital wards, &c., is to heat a platinum wire to incandescence by means of a Bunsen's coil.

The theory of the constitution of ozone, as also that of the volumetric relations subsisting between that body and oxygen, seem now to be established on a tolerably secure basis by the labours of Andrews and Tait, supplemented by those of Sorel. The first-named physicists observed that while only a small proportion of the oxygen experimented with could be converted into ozone at one time, a certain reduction of the volume of the gas attends the formation of each successive portion of this substance. By the application of heat the ozone was reconverted into oxygen, and the total volume of the gas resumed its first dimensions. They found that 100 volumes of oxygen, when acted on by the electric spark, contracted to 92 volumes, with the formation of ozone; and, strange to say, when the ozone thus formed was absorbed by mercury, 92 volumes of oxygen still remained. This process was continued, the residual 92 volumes were ozonized and thereby reduced to 84-82 volumes, the ozone thus formed again taken up by mercury, and still 84-82 volumes of oxygen remained behind. This latter phenomenon seemed inexplicable, but Dr. Odling accounted for the formation of the gas by the supposition that the molecule of ozone contains three atoms of oxygen, and, since the molecules of all gases are equal in volume, was, therefore, half as dense again as the molecule of oxygen, which contains only two atoms. Hence, when the 100 volumes of oxygen contracted to 92 volumes with formation of ozone, what took place was this :—1 molecule, 16 volumes, or 2 atoms of oxygen united with half a molecule, 8 volumes, or 1 atom of oxygen to form 1 molecule, two atoms, or 16 volumes of ozone, thereby diminishing the total bulk of the gas by 8 volumes, i. e. reducing the 100 volumes to 92 volumes. A similar process occurred with each successive formation of ozone. Odling further suggested that when the gas is acted upon by mercury it is only the third atom of the oxygen contained iu the molecule of ozone which is absorbed by the metal, the remaining two atoms being liberated as free oxygen, and the total volume of the gas, accordingly, remaining unchanged. This theory was confirmed by Soret, who, by using oil of turpentine as the absorbent

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