366 



NATURE 



{Mar. 12, 1874 



firmed. To determine, however, the actual amount of ozone in 

 the atmosphere is a problem of surpassing difficulty, on account 

 of the extremely small proportion in which it exists, even when 

 at a maximum. Its presence can be easily discovered by any of 

 the ordinary iodised starch- papers, or even more readily by 

 white bibulous ]5aper which has been moistened with a dilute 

 solution of iodide of potassium, and allowed to dry spontaneously 

 in a dark room. If a slip of this paper is exposed for five 

 minutes to a current of air, which will be often supplied by the 

 wind, or may be produced by walking briskly, it will be found 

 to have acquired a delicate red tint, if ozone be present even in 

 the smallest quantities. The tint wdl be best observed by com- 

 paring the shp after expo'sure with another slip of the same paper 

 which has not been exposed. Tlieactionof the diffused lightof day 

 on the paper is rarely perceptible after so short an exposure, but 

 this source of error can be easily avoided by enclosing the paper 

 in a hollow cylinder of wood. 



Although with the experimental resources now at our com- 

 mand, we can scarcely venture even to estimate the actual amount 

 of ozone at any lime present in the atmosphere, yet it may be 

 possible, as Schonbeia long ago proposed, by applying a chro- 

 matic scale to ihe indications of the test-papers, to ascertain ap- 

 proximately its relative amount in different localities, and its 

 variations in the same locality. Such estimates must, however, 

 be most uncertain, since the shades of colour produced on test- 

 paper hardly admit of being defined by numbers ; and in this 

 particular case they are liable to a special source of error, as there 

 can be little doubt that a large but unknown part of the ozone in 



Fig. 5- 



the air which comes into contact with the paper is catalytically 

 destroyed, and produces no chemical effect whatever. At the 

 same time the ozonometer, especially when used with an aspira- 

 tor, does unquestionably give indications of value regarding the 

 ozone states of the atmosphere, and till more accurate methods 

 are devised these observations ought cerlainly to be continued. 



Ozone is rarely found in the air of large towns, unless in a 

 suburb when the wind is blowing from the country ; and it is 

 only under the rarest and most exceptional conditions that it is 

 found in the air of the largest and best ventilated apartments. 

 It is, in fact, rapidly destroyed by smoke and other impurities 

 which are present in the air of localities where large bodies of 

 men have fixed their habitation, and I have often observed this 

 destructive action extending to a distance of one or two miles 

 from a manufacturing town, even in fine and bright weather. 



Ozone is rarely, if ever, absent in fine weather from the 

 air of the country, and it is more abundant, on the whole, in the 

 air of the mountain than of the plain. It is also said to occur 

 in larger quantity near the sea than in inland districts. It has 

 been found to an unusual amount after thunderstorms — a fact 

 whicli is favourable to the view that the presence of ozone in the 

 atmosphere is due to the action of the free electricity of the 

 latter on the oxygen of the air. The amount of ozone in the air 

 is greater, according to some observers, in winter than in sum- 

 mer, in spring than in autumn ; according to others, it is greater 

 in spring and summer than in autumn and winter. As regards 

 the influence of day and night, the observations do not all tell 



the same tale. Ozone has usually been found more abundantly 

 in the air at night than by day, but some careful observers have 

 found the reverse of this statement to be true. 



Schonbein was the first who attempted to connect the fluctu- 

 ations of atmospheric ozone with the prevalence or absence of 

 epidemic disease ; and since this suggestion was first published, 

 numerous observations have been made in different countries 

 with the view of ascertaining whether there is really any con- 

 nection between the indications of the ozonometer and the health 

 of a district. It has been asserted, for example, as the result of 

 observation, that an outbreak of cholera is accompanied by a 

 marked diminution of atmospheric ozone ; but this statement 

 has been disproved by later and more trustworthy observations. 

 On the whole, I think it may be safely asserted that no con- 

 nection has yet been proved to exi^t between the amount of 

 ozone in the atmosphere and the occurrence of epidemic or other 

 forms of disease. 



The permanent absence of ozone from the air of a locality 

 may, however, be regarded as a proof that we are breathing, if 

 I may venture to use the phrase, adulterated air. Its absence 

 from the air of towns, and of large rooms, even in the country, is 

 probably the chief cause of the difference which every one feels 

 when he breathes the air of a town, or of an apartment however 

 spacious, and afterwards inhales the fresh or ozone-containing 

 air of the open country. It is, indeed, highly probable that 

 many of the most important actions, by which the products of 

 vegetable and animal waste are removed by oxidation from the 

 air, are due to the action of ozone, and could not be effected by 

 ordinary or inactive oxygen. If the amount of ozone in the 

 atmosphere appear too small to produce such large results, we 

 must remember that, from its powerful affinities, ozone is being 

 continually used up, and must, therefore, be constantly re- 

 newed. 



The physiological action of ozone on the animal system is a 

 subject of interest, and I am able to state the general results of 

 two independent inquiries — one conducted a few years ago, by 

 Dr. Redfern, in Queen's College, Belfast, the other recently 

 communicated to this Society by Mr. Dewar and Dr. McKen- 

 drick. Dr. Redfern's experiments have not been published, but 

 he has kindly supplied me with the following note on the sub- 

 ject ; — *' The general results," hesavs, " I obtained from about 

 forty experiments conducted from May to September, 1857, to 

 find the effects of oxygen and ozone on different animals, are as 

 follows. The respiration for a very short time of oxygen, con- 

 taining about TiJuth part of ozone, is certainly fatal to all ani- 

 mals. The same gas, when passed over peroxide of manganese 

 and freed from ozone, is comparatively harmless, even when 

 respired for long periods. Respiration of such a mixture of 

 ozone for thirty seconds kills small animals, some dying after 

 respiring it only fifteen seconds, whilst similar animals will live 

 in good health for months after respiring oxygen alone for thirty- 

 seven hours, the carbonic acid being removed during the experi- 

 ment. Death is not due to the closure of the glottis, for it 

 occurs when a large opening has been made in the trachea. 

 Ozone causes death by producing intense congestion of the 

 lungs with emphysema, and distention of the right side of the 

 heart with fluid or coagulated blood, frequently attended by 

 convulsions. If ozone be rcpired in a dilute form, the animals 

 become drowsy and die quietly from coma, the condition of the 

 lungs and heart being the same, except that the emphysema is 

 less marked. Animals which have respired oxygen for more 

 than twelve hours will now and then die suddenly from the 

 formation of coagula in the heart, even after they have appeared 

 in good health for some days." 



The following are the conclusions which Mr. Dewar and 

 Dr. McKendrick have deduced from their researches. Inha- 

 lation of an atmosphere highly charged with ozone diminishes 

 the number of respirations per minute, and reduces the cardiac 

 pulsations in strength, the temperature of the animal being at 

 the same time lowered from 3° to 5° C. After death the blood 

 is found to be in a venous condition. Neither the capillary circu- 

 lation nor the reflex activity of the spinal cord is appreciably 

 affected. The same remark applies to the contractihty and worjc- 

 power of the muscles. Ozone acts on the coloured and colour- 

 less corpuscles of the frog like carbonic acid. Ciliary action is 

 not afiected by ozonised air or oxygen, but if the layer of liquid 

 be very thin, the ciha are readily destroyed. 



The thermal changes which accompany many of the reactions 

 of ozone are well marked, and their investigation, which has 

 been undertaken by Mr. Dewar, promises to yield a valuable 

 addition to our thermo-chemical knowledge. , 



