Let us briefly3 consider the history of ozone.
Nine years after Priestley had discovered oxygen, Van Marum, the electrician, noticed that when electric sparks are taken through that gas, a peculiar4 odour is evolved. Most people know this odour, since it is always to be recognized in the neighbourhood of an electrical machine in action. In reality, it indicates the presence of ozone in the air. But for more than half a century after Van Marum had noticed it, it was supposed to be the “smell of electricity.”
In 1840, Sch?nbein began to inquire into the cause of this peculiar odour. He presently found that it is due to some change in the oxygen; and that it can be produced in many ways. Of these, the simplest, and, in some respects, the most interesting, is the following:—“Take sticks of common phosphorus, scrape them until they have a metallic5 lustre6, place them in this condition under a large bell-jar, and half-cover them with water. The air in the bell-jar is348 soon charged with ozone, and a large room can readily be supplied with ozonized air by this process.”
Sch?nbein set himself to inquire into the properties of this new gas, and very interesting results rewarded his researches. It became quite clear, to begin with, that whatever ozone may be, its properties are perfectly7 distinct from those of oxygen. Its power of oxidizing or rusting8 metals, for example, is much greater than that which oxygen possesses. Many metals which oxygen will not oxidize at all, even when they are at a high temperature, submit at once to the influence of ozone. But the power of ozone on other substances than metals is equally remarkable9. Dr. Richardson states that, when air is so ozonized as to be only respirable for a short time, its destructive power is such that gutta-percha and india-rubber tubings are destroyed by merely conveying it.
The bleaching10 and disinfecting powers of ozone are very striking. Sch?nbein was at first led to associate them with the qualities of chlorine gas; but he soon found that they are perfectly distinct.
It had not yet been shown whether ozone was a simple or a compound gas. If simple, of course it could be but another form of oxygen. At first, however, the chances seemed against this view; and there were not wanting skilful11 chemists who asserted that ozone was a compound of the oxygen of the air with the hydrogen which forms an element of the aqueous vapour nearly always present in the atmosphere.
It was important to set this question at rest. This was accomplished12 by the labours of De la Rive and Marignac, who proved that ozone is simply another form of oxygen.
Here we touch on a difficult branch of modern chemical research. The chemical elements being recognized as the simplest forms of matter, it might be supposed that each element would be unchangeable in its nature. That a compound should admit of change, is of course a thing to be expected. If we decompose13 water, for instance, into its349 component14 elements, oxygen and hydrogen, we may look on these gases as exhibiting water to us in another form. And a hundred instances of the sort might be adduced, in which, either by separating the elements of a compound, or by re-arranging them, we obtain new forms of matter without any real change of substance. But with an element, the case, one would suppose, should be different.
However, the physicist15 must take facts as he finds them; and amongst the most thoroughly recognized chemical facts we have this one, that elementary substances may assume different forms. Chemists call the phenomenon allotropy. A well-known instance of allotropy is seen in red phosphorus. Phosphorus is one of the chemical elements; and, as every one knows, the form in which it is usually obtained is that of a soft, yellow, semi-transparent solid, somewhat resembling bees’ wax in consistence, poisonous, and readily taking fire. Red phosphorus is the same element, yet differs wholly in its properties. It is a powder, it does not readily take fire, and it is not poisonous.
Ozone, then, is another form of oxygen. It is the only instance yet discovered of gaseous16 allotropy.
And now we have to deal with the difficult and still-vexed questions of the way in which the change from oxygen is brought about, and the actual distinction between the two forms of the same gas. Sch?nbein held that common oxygen is produced by the combination of two special forms of oxygen—the positive and the negative, or, as he called them, ozone and antozone. He showed that, in certain conditions of the air, the atmospheric17 oxygen exhibits qualities which are the direct reverse of those which ozone exhibits, and are distinct from those of ordinary oxygen. In oxygen thus negatived or antozonized, animals cannot live any more than they can in nitrogen. The products of decomposition18 are not only not destroyed as by ozone, but seem subject to preservative19 influences, and speedily become singularly offensive; dead animal matter rapidly putrefies, and wounds show a tendency to mortification20.
350 But the theory of positive and negative forms of oxygen, though still held by a few physicists21, has gradually given way before the advance of new and sounder modes of inquiry22. It has been proved, in the first place, that ozone is denser23 than ordinary oxygen. The production of ozone is always followed by a contraction24 of the gas’s volume, the contraction being greater or less according to the amount of oxygen which has been ozonized. Regularly as the observers—Messrs. Andrews and Tait—converted a definite proportion of oxygen into ozone, the corresponding contraction followed, and as regularly was the original volume of the gas restored when, by the action of heat, the ozone was reconverted into oxygen.
And now a very singular experiment was made by the observers, with results which proved utterly25 perplexing to them. Mercury has the power of absorbing ozone; and the experimenters thought that if, after producing a definite contraction by the formation of ozone, they could absorb the ozone by means of mercury, the quantity of oxygen which remained would serve to show them how much ozone had been formed, and thence, of course, they could determine the density26 of ozone.
Suppose, for instance, that we have one hundred cubic inches of oxygen, and that by any process we reduce it to a combination of oxygen and ozone occupying ninety-five cubic inches. Now, if the mercury absorbed the ozone, and we found, say, that there only remained eighty-five cubic inches of oxygen, we could reason in this way:—Ten cubic inches were occupied by the ozone before the mercury absorbed it; but these correspond to fifteen cubic inches of oxygen; hence, ozone must be denser than oxygen in the proportion of fifteen to ten, or three to two. And whatever result might have followed, a real absorption of the ozone by the mercury would have satisfactorily solved the problem.
But the result actually obtained did not admit of interpretation27 in this way. The apparent absorption of the351 ozone by the mercury, that is, the disappearance28 of the ozone from the mixture, was accompanied by no diminution29 of volume at all. In other words, returning to our illustrative case, after the absorption of the ozone from the ninety-five cubic inches occupied by the mixture, there still remained ninety-five cubic inches of oxygen; so that it seemed as though an evanescent volume of ozone corresponded in weight to five cubic inches of oxygen. This solution, of course, could not be admitted, since it made the density of ozone infinite.
The explanation of this perplexing experiment is full of interest and instruction. The following is the account given by Mr. C. W. Heaton (Professor of Chemistry at Charing30 Cross Hospital), slightly modified, however, so that it may be more readily understood.
Modern chemists adopt, as a convenient mode of representing the phenomena31 which gases exhibit, the theory that every gas, whether elementary or compound, consists of minute molecules33. They suppose that these molecules are of equal size, and are separated by equal intervals34 so long as the gas remains35 unchanged in heat and density. This view serves to account for the features of resemblance presented by all gases. The features in which gases vary are accounted for by the theory that the molecules are differently constituted. The molecules are supposed to be clusters of atoms, and the qualities of a gas are assumed to depend on the nature and arrangement of these ultimate atoms. The molecules of some elements consist but of a single atom; the molecules of others are formed by pairs of atoms; those of others by triplets; and so on. Again, the molecules of compound gases are supposed to consist of combinations of different kinds of atoms.
Now, Dr. Odling, to whom we owe the solution of the perplexing problem described above, thus interpreted the observed phenomena. A molecule32 of oxygen contains two atoms, one of ozone contains three, and the oxidizing power of ozone depends on the ease with which it parts with its third352 atom of oxygen. Thus, in the experiment which perplexed36 Messrs. Andrews and Tait, the mercury only seemed to absorb the ozone; in reality it converted the ozone into oxygen by removing its third atom. And now we see how to interpret such a result as we considered in our illustrative case. Five cubic inches of oxygen gave up their atoms, each atom combining with one of the remaining oxygen doublets, so as to form a set of ozone triplets. Clearly, then, fifteen cubic inches of oxygen were transformed into ozone. They now occupied but ten cubic inches; so that the mixture, or ozonized oxygen, contained eighty-five cubic inches of oxygen and ten of ozone. When the mercury was introduced, it simply transformed all the ozone triplets into oxygen doublets, by taking away the odd atom from each. It thus left ten cubic inches of oxygen, which, with the remaining eighty-five, constituted the ninety-five cubic inches observed to remain after the supposed absorption of the ozone.
It follows, of course, that ozone is half as heavy again as oxygen.
But, as Mr. Heaton remarked, “this beautiful hypothesis, although accounting37 perfectly for all known facts, was yet but a probability. One link was lacking in the chain of evidence, and that link M. Soret has supplied by a happily devised experiment.” Although mercury and most substances are only capable of converting ozone into oxygen, oil of turpentine has the power of absorbing ozone in its entirety. Thus, when the experiment was repeated, with oil of turpentine in place of the mercury, the ozone was absorbed, and the remaining oxygen, instead of occupying ninety-five inches, occupied but eighty-five. After this, no doubt could remain that Dr. Odling’s ingeniously conceived hypothesis was the correct explanation of Messrs. Andrews and Tait’s experiment.
We recognize, then, in ozone a sort of concentrated oxygen, with this peculiar property, that it possesses an extraordinary readiness to part with its characteristic third353 atom, and so disappear as ozone, two-thirds of its weight remaining as oxygen.
It is to this peculiarity38 that ozone owes the properties which render it so important to our welfare. We are indeed, as yet, in no position to theorize respecting this element, our knowledge of its very existence being so recent, and our information respecting its presence in our atmosphere being of still more recent acquisition.
Indeed, it is well remarked by Mr. Heaton, that we had, until quite lately, no reason for confidently adopting Sch?nbein’s view that ozone exists in our atmosphere. The test-papers which Sch?nbein made use of turned blue under the influence of ozone, it is true, but they were similarly influenced by other elements which are known to exist in our atmosphere, and even the sun’s rays turned them blue. However, Dr. Andrews has shown how the character of the air producing the change can be further tested, so as to render it certain that ozone only has been at work. If air which colours the test-papers be found to lose the property after being heated, the change can only be due to ozone, because nitrous and nitric acids (which have the power of colouring the test-papers) would not be removed by the heat, whereas ozone is changed by heat into oxygen.
Once we are certain that ozone exists in the air, we must recognize the fact that its presence cannot fail to have an important bearing on our health and comfort; for ozone is an exceedingly active agent, and cannot exist anywhere without setting busily to its own proper work. What that work is, and whether it is beneficial or deleterious to ourselves, remains to be considered.
In the first place, ozone has immense power as a disinfectant. It decomposes39 the products emanating40 from putrefying matter more effectually than any other known element. Perhaps the most striking proof ever given of its qualities in this respect is that afforded by an experiment conducted by Dr. Richardson a few years ago.
He placed a pint41 of blood taken from an ox in a large354 wide-mouthed bottle. The blood had then coagulated, and it was left exposed to the air until it had become entirely42 redissolved by the effects of decomposition. At the end of a year the blood was put into a stoppered bottle, and set aside for seven years. “The bottle was then taken from its hiding-place,” says Dr. Richardson, “and an ounce of the blood was withdrawn43. The fluid was so offensive as to produce nausea44 when the gases evolved from it were inhaled45. It was subjected by Dr. Wood and myself to a current of ozone. For a few minutes the odour of ozone was destroyed by the odour of the gases from the blood; gradually the offensive smell passed away; then the fluid mass became quite sweet, and at last a faint odour of ozone was detected, whereupon the current was stopped. The blood was thus entirely deodorized; but another and most singular phenomenon was observed. The dead blood coagulated as the products of decomposition were removed, and this so perfectly, that from the new clot46 that was formed serum47 exuded48. Before the experiment commenced, I had predicted on theoretical grounds that secondary coagulation49 would follow on purification; and this experiment, as well as several others afterwards performed, verified the truth of the prediction.”
It will of course be understood that ozone, in thus acting50 as a disinfectant, is transformed into oxygen. It parts with its third atom as in the mercury experiment, and so loses its distinctive51 peculiarity. Thus we might be led to anticipate the results which come next to be considered.
Ozone has certain work to do, and in doing that work is transmuted52 into oxygen. It follows, then, that where there has been much work for ozone to do, there we shall find little ozone left in the air. Hence, in open spaces where there is little decomposing53 matter, we should expect to find more ozone than in towns or cities. This accords with what is actually observed. And not only is it found that country air contains more ozone than town air, but it is found that air which has come from the sea has more ozone than even355 the country air, while air in the crowded parts of large cities has no ozone at all, nor has the air of inhabited rooms.
So far as we have gone, we might be disposed to speak unhesitatingly in favour of the effects produced by ozone. We see it purifying the air which would otherwise be loaded by the products of decomposing matter, we find it present in the sea air and the country air which we know to be so bracing54 and health-restoring after a long residence in town, and we find it absent just in those places which we look upon as most unhealthy.
Again, we find further evidence of the good effects of ozone in the fact that cholera55 and other epidemics56 never make their dreaded57 appearance in the land when the air is well supplied with ozone—or in what the meteorologists call “the ozone-periods.” And though we cannot yet explain the circumstance quite satisfactorily, we yet seem justified58 in ascribing to the purifying and disinfecting qualities of ozone our freedom at those times from epidemics to which cleanliness and good sanitary59 regulations are notedly inimical.
But there is a reverse side to the picture. And as we described an experiment illustrating60 the disinfecting qualities of ozone before describing the good effects of the element, we shall describe an experiment illustrating certain less pleasing qualities of ozone, before discussing the deleterious influences which it seems capable of exerting.
Dr. Richardson found that when the air of a room was so loaded with ozone as to be only respirable with difficulty, animals placed in the room were affected61 in a very singular manner. “In the first place,” he says, “all the symptoms of nasal catarrh and of irritation62 of the mucous63 membranes64 of the nose, the mouth, and the throat were rapidly induced. Then followed free secretion65 of saliva66 and profuse67 action of the skin—perspiration. The breathing was greatly quickened, and the action of the heart increased in proportion.” When the animals were suffered to remain yet longer within the room, congestion68 of the lungs followed,356 and the disease called by physicians “congestive bronchitis” was set up.
A very singular circumstance was noticed also as to the effects of ozone on the different orders of animals. The above-mentioned effects, and others which accompanied them, the description of which would be out of place in these pages, were developed more freely in carnivorous than in herbivorous animals. Rats, for example, were much more easily influenced by ozone than rabbits were.
The results of Dr. Richardson’s experiments prepare us to hear that ozone-periods, though characterized by the absence of certain diseases, bring with them their own forms of disease. Apoplexy, epilepsy, and other similar diseases seem peculiarly associated with the ozone-periods, insomuch that eighty per cent. of the deaths occurring from them take place on days when ozone is present in the air in larger quantities than usual. Catarrh, influenza69, and affections of the bronchial tubes, also affect the ozone-periods.
We see, then, that we have much yet to learn respecting ozone before we can pronounce definitively70 whether it is more to be welcomed or dreaded. We must wait until the researches which are in progress have been carried out to their conclusion, and perhaps even then further modes of inquiry will have to be pursued before we can form a definite opinion.
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1
ozone
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| n.臭氧，新鲜空气 | |
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thoroughly
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| adv.完全地，彻底地，十足地 | |
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3
briefly
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| adv.简单地，简短地 | |
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peculiar
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| adj.古怪的，异常的；特殊的，特有的 | |
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5
metallic
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| adj.金属的；金属制的；含金属的；产金属的；像金属的 | |
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6
lustre
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| n.光亮，光泽；荣誉 | |
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7
perfectly
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| adv.完美地，无可非议地，彻底地 | |
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8
rusting
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| n.生锈v.（使）生锈( rust的现在分词 ) | |
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9
remarkable
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| adj.显著的，异常的，非凡的，值得注意的 | |
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10
bleaching
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| 漂白法，漂白 | |
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skilful
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| (=skillful)adj.灵巧的，熟练的 | |
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12
accomplished
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| adj.有才艺的；有造诣的；达到了的 | |
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13
decompose
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| vi.分解；vt.（使）腐败，（使）腐烂 | |
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14
component
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| n.组成部分，成分，元件；adj.组成的，合成的 | |
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15
physicist
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| n.物理学家，研究物理学的人 | |
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16
gaseous
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| adj.气体的，气态的 | |
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atmospheric
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| adj.大气的，空气的；大气层的；大气所引起的 | |
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18
decomposition
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| n. 分解, 腐烂, 崩溃 | |
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19
preservative
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| n.防腐剂；防腐料；保护料；预防药 | |
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mortification
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| n.耻辱，屈辱 | |
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physicists
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| 物理学家( physicist的名词复数 ) | |
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inquiry
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| n.打听，询问，调查，查问 | |
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23
denser
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| adj. 不易看透的, 密集的, 浓厚的, 愚钝的 | |
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contraction
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| n.缩略词，缩写式，害病 | |
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utterly
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| adv.完全地，绝对地 | |
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density
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| n.密集，密度，浓度 | |
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interpretation
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| n.解释，说明，描述；艺术处理 | |
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disappearance
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| n.消失，消散，失踪 | |
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diminution
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| n.减少；变小 | |
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charing
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| n.炭化v.把…烧成炭，把…烧焦( char的现在分词 )；烧成炭，烧焦；做杂役女佣 | |
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phenomena
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| n.现象 | |
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molecule
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| n.分子，克分子 | |
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molecules
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| 分子( molecule的名词复数 ) | |
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intervals
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| n.[军事]间隔( interval的名词复数 )；间隔时间；[数学]区间；（戏剧、电影或音乐会的）幕间休息 | |
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remains
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| n.剩余物，残留物；遗体，遗迹 | |
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perplexed
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| adj.不知所措的 | |
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accounting
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| n.会计，会计学，借贷对照表 | |
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peculiarity
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| n.独特性，特色；特殊的东西；怪癖 | |
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decomposes
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| 腐烂( decompose的第三人称单数 )； （使）分解； 分解（某物质、光线等） | |
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emanating
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| v.从…处传出，传出( emanate的现在分词 )；产生，表现，显示 | |
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pint
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| n.品脱 | |
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entirely
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| ad.全部地，完整地；完全地，彻底地 | |
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43
withdrawn
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| vt.收回；使退出；vi.撤退，退出 | |
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nausea
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| n.作呕，恶心；极端的憎恶(或厌恶) | |
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inhaled
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| v.吸入( inhale的过去式和过去分词 ) | |
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clot
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| n.凝块；v.使凝成块 | |
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serum
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| n.浆液，血清，乳浆 | |
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48
exuded
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| v.缓慢流出，渗出，分泌出( exude的过去式和过去分词 )；流露出对（某物）的神态或感情 | |
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coagulation
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| n.凝固；凝结物 | |
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50
acting
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| n.演戏，行为，假装；adj.代理的，临时的，演出用的 | |
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distinctive
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| adj.特别的，有特色的，与众不同的 | |
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transmuted
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| v.使变形，使变质，把…变成…( transmute的过去式和过去分词 ) | |
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decomposing
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| 腐烂( decompose的现在分词 )； （使）分解； 分解（某物质、光线等） | |
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bracing
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| adj.令人振奋的 | |
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cholera
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| n.霍乱 | |
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epidemics
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| n．流行病 | |
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dreaded
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| adj.令人畏惧的；害怕的v.害怕，恐惧，担心( dread的过去式和过去分词) | |
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justified
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| a.正当的，有理的 | |
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sanitary
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| adj.卫生方面的，卫生的，清洁的，卫生的 | |
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illustrating
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| 给…加插图( illustrate的现在分词 )； 说明； 表明； （用示例、图画等）说明 | |
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affected
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| adj.不自然的，假装的 | |
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irritation
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| n.激怒，恼怒，生气 | |
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mucous
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| adj. 黏液的，似黏液的 | |
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membranes
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| n.（动物或植物体内的）薄膜( membrane的名词复数 )；隔膜；（可起防水、防风等作用的）膜状物 | |
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secretion
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| n.分泌 | |
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saliva
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| n.唾液，口水 | |
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profuse
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| adj.很多的，大量的，极其丰富的 | |
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congestion
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| n.阻塞，消化不良 | |
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influenza
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| n.流行性感冒，流感 | |
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definitively
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| adv.决定性地，最后地 | |
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