The conclusion drawn from this experiment is, that the ozone destroyed the miasm by oxidation, and could only make its presence evident after the complete destruction of the noxious volatile substances. This effect is more strikingly shewn by another experiment.
A balloon of similar capacity to the one above mentioned was charged as strongly as possible with ozone, and afterwards washed with water. The same piece of flesh was suspended within it; and the opening being carefully closed, it was left inside for nine hours before the air of the balloon presented the least odour of putrefaction. The air was tested every thirty minutes by an ozonometer, and the proportion of ozone found to be gradually diminishing; but as long as the paper of the instrument exhibited the slightest trace of blue, there was no smell, which only came on as the last signs of ozone disappeared. Thus, all the miasm given off by the piece of flesh during nine hours was completely neutralised by the ozone with which the balloon had been impregnated, so small in quantity as to be but the 6000th part of a gramme. One balloon filled with ozonified air, would suffice to disinfect 540 balloons filled with miasmatic air. 'These considerations,' says M. Schoenbein, 'shew us how little the miasma of the air are to be appreciated by weight, even when they exist therein in a quantity very sensible to the smell, and how small is the proportion of ozone necessary to destroy the miasm produced by the putrefaction of organic substances, and diffused through the atmosphere.'
The presence of ozone in any vessel or in the atmosphere, may be detected by a test-paper which has been moistened with a solution composed of 1 part of pure iodide of potassium, 10 parts of starch, and 100 parts of water, boiled together for a few moments. Paper so prepared turns immediately blue when exposed to the action of ozone, the tint being lighter or darker according to the quantity. Schoenbein's ozonometer consists of 750 slips of dry bibulous paper prepared in the manner described; and with a scale of tints and instructions, sufficient to make observations on the ozone of the atmosphere twice a day for a year. After exposure to the ozone, they require to be moistened to bring out the colour.
M. Schoenbein continues: 'We must admit that the electric discharges which take place incessantly in different parts of the atmosphere, and causing therein a formation of ozone, purify the air by this means of organic, or, more generally, oxidizable miasma; and that they have thus the important office of maintaining it in a state of purity suitable to animal life. By means of atmospheric electricity, and, indirectly, nature thus attains on a great scale the object that we sometimes seek to accomplish in a limited space by fumigations with chlorine.
'Here, as in many other cases, we see nature effecting two different objects at one stroke. For if the oxidizable miasma are destroyed by atmospheric ozone, they, in turn, cause the latter to disappear, and we have seen that it is itself a miasm. This is doubtless the reason why ozone does not accumulate in the atmosphere in greater proportion than the oxidizable miasma, notwithstanding the constant formation of one and the other.
'In all times, the idea has been held, that storms purify the air, and I do not think that this opinion is ill-founded. We know, in fact, that storms give rise to a more abundant production of ozone. It is possible, and even probable, that sometimes, in particular localities, there may not be a just relation between the ozone and the oxidizable miasma in the air, and that the latter cannot be completely destroyed. Hence, in accordance with the chemical nature and physiological influence of these miasma, they would exert a marked action on the animal economy, and cause diseases among the greater number of those who breathe the infected air. But numerous experiments prove that, as a rule, the air contains free ozone, though in very variable proportions; from which we may conclude that no oxidizable miasm—sulphuretted hydrogen, for example—can exist in such an atmosphere, any more than it could exist in air containing but a trace of chlorine.
'I do not know if it be true, as has been advanced by Mr Hunt and other persons, that ozone is deficient in the atmospheric air when some wide-spread malady, such as cholera, is raging. In any case, it would be easy, by means of the prepared paper, to determine the truth or fallacy of this opinion.
'There is one fact which should particularly engage the attention of physicians and physiologists, which is, that, of all seasons, the winter is distinguished by the greatest proportion of ozone; whence it follows, that during that season the air contains least of oxidizable miasma. We can say, therefore, with respect to this class of miasma, that the air is purer in winter than in summer.
'All my observations agree in shewing, that the proportion of ozone in the air increases with the height; if this fact be general, as I am disposed to believe, we must consider the upper regions of the atmosphere as purer, with regard to oxidizable miasma, than the lower.
'The appearance of certain maladies—intermittent fever, for example—appears to be connected with certain seasons and particular geographical conditions. It would be worth while to ascertain, by ozonometric observations, whether these physiological phenomena have any relation whatever with the proportion of ozone contained in the air in which they occur.