Ozone
Ozone
18th April 2023
by William Tullett
Created at:
18th April 2023
Creator:
William Tullett
Citation:
[click to copy]
Ozone
Smells
The word ozone did not exist until 1840, when the German chemist Christian Friedrich Schöbein needed a term for the strange odour given off by electric sparks passing through dry air. Given that the most distinctive sensory property of this new gas was its odour, Schöbein devised the word ‘ozone’ from the Greek ozein, meaning ‘to smell’. Variously described as pungent or fresh ozone is a molecule composed, as would later be determined in 1865, of 3 oxygen atoms. It has been associated with the smell after thunder and lightning storms and the scent of fresh country air. Initially held to possess miracuolous health-giving properties, ozone was widely deployed in a variety of spaces in the late nineteenth and early twentieth century and various inventions were deployed to generate and capture it. However, there by the 1920s there was increasing scepticism about the utility of ozone and more and more evidence that its influence on the human body could be highly negative. Despite this, the scent of ozone was continually deployed in novels and travel accounts to evoke the refreshing and healthy airs of nature in forests, at sea, and on top of mountains.
Odeuropa Smell Explorer
Smells
Looking back after the identification and naming of ozone, nineteenth-century authors suggested that the 'sulpheorus' and 'fearful' smells of thunderbolts in ancient texts such as Homer's Odyssey and Iliad were the produced by ozone (Fox, 1873: 3). But history of ozone’s naming and popularization truly begins with the history of electricity. The eighteenth-century was a period of extensive electrical experimentation, as scientists explored the possibilities that electricity might yield for understanding the body and maintaining health. In these experiments a strange smell often appeared. In 1768 the English polymath and pneumatic chemist Joseph Priestly that electricity was sensible to smell. If a person took a pointed brass rod that had been electrified and put it within inches of their nose they would 'feel a strong and disagreeable smell, like that of burning sulphur' (Priestley, 1768: 19). In 1774 William Hooper described the 'faint phosphoreal smell' of electricity (Hooper, 1774) and the Italian chemist and physician Tiberius Cavallo also suggested that when an electrically charged object was presented to the nostrils an individual they 'would be affected by a smell, much resembling that of phosphorous' (Cavallo, 1777: 40).

Experimenters quickly realised that the smell given off by electricity was very similar to that given off by thunder and lightning. In 1762 a recent stroke victim Reverend Winder of Halsted, Essex, was asleep when his house was struck by lightning and filled his bedroom with a 'strong phosphorous smell' (Wesley, 1777: 236). By the end of the eighteenth century this was consistently referred to as an ‘electrical odour’ or ‘electrical smell, as in one set of experiments on metalloids where the ‘electrical odour’ was described as similar to ‘the smell that is frequently pereceived in the atmosphere after storms’ (Weiss, 1809: 367).

As the ‘electrical’ smell that first emerged from experimental descriptions became familiar it began to be used more frequently as a descriptor in meteorological observations. For example, in Cambridge on March 28th 1813 Thomas Forster of Corpus Christi college observed that 'There was a strong electric smell at night like the smell after showers have fallen on dry ground in summer' (Forster, 1813: 319). Similarly, at Tottenham on the 10th of September 1815 Luke Howard recorded 'somewhat hazy air, with a smell of electricity' (Howard, 1815: 320). The association of this scent with pure air was also apparent by 1800, when Antoine-François de Fourcroy noted that 'the smell of electricity is often perceived by sedentary people, when they go into the open air' (Fourcroy, 1800: 198).

Finally, in 1840 the German chemist Christian Friedrich Schöbein gave the smell its name: ozone. What ensued was a massive popularisation of the term to describe healthy smells. In 1865 Glasgow newspaper readers were given the most common reference point for ozone: if 'during a thunderstorm, you have ever been in the neighbourhood of an object that has been struck by lightning, you will have become familiar with a peculiar pungent sulphurous or phosphorous smell... that pervades the air'. This was ozone (Glasgow Herald, 1865). This was the initial reference used by Schönbein himself, who noted the presence of ozonic odours when his servant was hit by lighting in a tent on a Swiss mountain (Fox, 1873: 4) and associated ‘the smell with that accompanying a flash of lightning during a storm on the Jura' (Fox, 1873: 6).

But increasingly the topographical and material referents for ozone expanded. Country, mountain-top, forest and sea-side air were all, by the late nineteenth century, held to be full of ozone. In the 1880s experiments were made to more accurately measure the threshold of detection for the scent of ozone. Here the smell changed as the concentration of ozone altered: from the 'distinct odour that reminded 'one of the air on the South Downs during a south-west breeze', to the smell of usual fresh air, and finally to the point where the smell disappeared completely (Hartley, 1881: 121-2).

It was even suggested that ozone was source of the prophylactic powers that enabled herbs, flowers, and spices to ward off disease. In an article in 1872 Paolo Mantegazza, a Professor at Padua, argued that power of odoriferous herbs and flowers as plague preventatives resided in the large quantity of ozone that they discharged. The essences of these plants, as used in perfumes, contained the largest amount of ozone (Mategazza, 1870). Having read this, the New-York Unitarian minister Charles H. Brigham thus surmised that the 'boudoir of a fashionable lady… well supplied with perfume bottles and bouquets is a factory of ozone' (Brigham, 1874, 262). By contrast, it was claimed that if substances such as cinnamon or turpentine lost their odour then exposure to ozone could allow them to 'gain a kind of freshness'. Ozone might thus extend or increase the odour of fragrant materials (Richardson, 1889).
As the number of experiments on ozone further expanded, knowledge of its smell meant that it was often used as a descriptor in other experimental contexts. To give one example among many, in 1907, radium chloride kept enclosed in dry air for 3-4 days took on a 'marked smell of ozone' (Thorpe, 1908: 308). By 1920 the widespread invocation of ozone in a multitude spaces and practices from domestic cleaning to industrial production and from laboratory science to the storage of refrigerated food, meant that there was less and less certainty about its precise smell. Eric Keightley Rideal, who published a whole book on ozone in 1920, noted:

that there is no unanimity in describing this odour, since it has been likened to sulphur, chlorine and phosophorus… other observers have compared it to dilute oxides of nitrogen, whilst De la Coux likens it to lobster (Rideal, 1920: 5-6).

Another book-length treatment of ozone suggested that 'the best we can do is to say that ozone smells like ozone' because it is 'so definite and strong that it really is entitled to be considered an individual smell’ (Vosamaer, 1916: 6). If it was anything, ozone was a unique example of a smell that that entered into the consciences of people and a whole web of conceptual contexts by virtue of its being given a name.
Places
It was, by 1905, 'a generally cherished idea that ozone is accountable for the health-giving properties of sea or mountain air' (Anon, 1905: 1195). Country air was held to be particularly full of ozone. This might appear inodorous when one was long habituated to it. But if a person had been 'subjected for many hours to a vitiated atmosphere' only to then experience a 'whiff of the purest country air' the presence of ozone would be immediately apparent (Fox, 1873: 143).

Forests and lush landscapes were held to be repositories of ozone. In both European and American novels, the prairies of the American West were said to be home to 'miraculous air, heady with ozone and made memorably sweet by leagues of wild flowerets' (Porter, 1907). Characters trapsing across America 'smelt the ozone of the West, where sandy plains melted into the horizon' (Baxter, 1920). The connection of turpentine with ozone production would, one writer to Nature argued, immediately 'bring to the mind of the tourist the freshness of the air of hills planted with pine forests' (Nubibus, 1874: 382). Walking in the Maine woods, characters breathed in the 'pure, exhilarating ozone and fragrant odors of pine-balsam' (Hornibrook, 1897). European forests were also full of ozone. The air of the Erzgebirge hills in Germany thought to be 'rich in ozone and aromatic of pine woods' (Anon, 1908).

An article on English seaside sanitoria argued that 'the peculiar smell perceived at the seaside ought to teach persons even utterly ignorant of medicine that the air there possesses virtues and properties quite different to the air of continents’ (E. S. D., 1870: 228). Given that the 'peculiar odour of sea-air' was said to be due to ozone, it was 'readily perceived in travelling by rail from some inland place towards the coast' (Fox, 1873: 143). On an autumnal visit to the Irish coast, it was said that you could 'smell the ozone strong as violets' (Thurston, 1910). At Kissingen, to the north west of Germany, natural salt-water springs filled the air with water spray and its odour was 'popularly likened to that of the sea shore'. Ozone was held to be the culprit (Fox, 1873: 110). Posters promoting sea-side tourism therefore jumped on ozone to promote beaches and resorts.

Figure 1. Chromolitho card advertisingt the Philadelphia-based Drs Starkey and Palen's 'Compound Oxygen', supposedly containing ozone, as a miraculous cure, 1886, 11 x 16c, EPH3006, Wellcome Collection, London.


However, once ozone had been identified and its production by electric means explored, there were plenty of calls to use it in a variety of public and private spaces. Perhaps the most obvious were public halls and theatres where people gathered in large numbers. In 1910 the new 'Ozonair' company in London produced a series of compact osonizers that could be used in large rooms. An article on the company argued that ‘in a crowded hall the atmosphere of a public meeting would stand to gain enormously by the freshening and purifying effects of one or two well-placed ozonisers’ (Anon, 1910a). The air produced by these ozone generators was said to impart a 'delightful refreshing sensation' and relieve 'the air of all oppression and stuffiness' that would be appreciated in 'crowded places, churches, public halls, theatres, clubs, workshops, steamships' (Anon, 1910b).The discomfort from attendant on a lack of ventilation was due to ‘the nausea caused by the odour emitted from an imperfectly washed crowd’ and the value of ozone therefore depended ‘largely upon its power of removing this odour’ (Hill, 1912: 72). In Karlsruhe in 1908 an ozone generating apparatus was set up in the ventilation system of the Court Theatre and was felt to be beneficial. It was noted that 'especially after the breaks one can clearly smell the refreshing smell of ozone' and the 'unpleasant' smells that filled the theatre when it was sold out or during long performances could no longer be detected (Anon, 1908: 6). 

Figure 2. Ozone generaetor, produced by Compagnie de l'ozone, Rue Elise Bruxelles, 1900-1950, Rijksmuseum Boerhaave.

Ozone was also used on transport networks. Since it had opened in 1900 the Central London Railway had been unfavourably compared to other underground railways. One writer noted that:

In Paris on a hot day, it is positively refreshing to meet the cool breeze escaping from each station, the air having an odour of a clean-smelling and not unpleasant disinfectant in place of the stuffy hot smell of the Central London Railway (Wordingham, 1902: 672).

In London, ozone was therefore successfully used to take away the 'unpleasant smell of the Central Tube railway' (Hill, 1913) and the railway made a point of this by advertising that ‘Father Neptune’ would blow ’80 million cubic feet of ozone’ through the underground tunnels on a daily basis. In 1960 the poet John Betjeman recalled the smell of summers spent on the London underground between 1916 and 1921:

The Central London, with its cut-glass shades
On draughty stations, had an ozone smell –
Not seaweed-scented ozone from the sea
But something chemical from Birmingham. (Gilbert, 2012: 111

But ozone generators were also advertised for home use. The 'Kriens Ozogenerator' advertised in 1909 asked newspaper readers 'have you ever thought about what air you breathe during your nightly sleep?'. It informed the possibly now slightly anxious audience that this air 'becomes useless and harmful to human health'. The solution was an ozone generator that replaced the oxygen respired by the sleeper, got rid of carbon dioxide, and replaced the foul odours with ‘the refreshing smell of the coniferous forest’ (Anon, 1909: 16). Part of the claim was thus that by generating ozone you were bringing the healthy qualities of natural environments into the home. Adverts could be found for 'Conifer Spirit or Ozone Fir-Forest Air' which was claimed to purify rooms from bad smells and cured respiratory illnesses 'just as excellently as staying in coniferous forests' (Anon, 1882: 15). Clearly the idea that ozone was the smell of healthy air was widespread and at least some households contained working ozone generators. In a German newspaper article from May 1912, reported that 'many people believe that an apparatus for generating ozone can improve the air in their homes considerably and permanently' (Anon, 1912: 9). Ozone might be encouraged into both homes and hospitals in other ways. Thomas Moffatt argued that ozone was 'nature's disinfectant' and that oil of juniper and turpentine, when oxidized, both produced large amounts of ozone. His recommendations were that furniture might be polished with beeswax and turpentine to render it the air of a room 'fresh and ozonic', all furniture should be made of pine wood, and all cesspools surrounded by with fir trees and juniper shrubs (Moffatt, 1877: 254).

The suggested uses for ozone kept on proliferating. In 1899 it was suggested that ozone could ‘destroy the evil smells’ of the House of Commons (Anon, 1899: 1245) and in 1905 it was argued that the ‘peculiar and refreshing smell of ozone’ would make it a useful deodorizer of public lavatories rather than the ‘sickly smell of chlorine compounds and tar acids’ (Anon, 1905: 1444). In Germany ozone ventilation systems were 'almost always used on larger' navy and passenger ships - initially for keeping recreation rooms smelling sweet and later for storing food and drinking water. The ozone in the sea air was therefore matched by extra ozone throughout the indoor spaces of ships (Anon, 1927: 9).
Practices
In most of these cases the use of ozone was largely for the purposes of deodorizating, disinfecting and refreshing the air. By the 1920s ozone was being widely used in the oil, fat, and wax industries to remove bad odours and flavours. Bone fact, cod oil, and tallow were some of the substances deodorized by the application of ozone (Rideal, 1920: 160-3). Given its germicidal and deodorizing properties, ozone was also used for sterilized water supplies, treating wounds, and in preserving and storing cold meat (Rideal, 1920: 13). Many companies were formed in the late nineteenth and early twentieth century to market these uses of ozone, including the Compagnie des eaux et de l'ozone, founded in 1907 by Marius-Paul Otto of Nice in order to market the sterilizing of drinking water through ozone. In 1899 The Lancet printed a discussion of an ozonator for use in hospitals and sick rooms that would be 'extremely useful as a deodorant of feotid discharges or evacuations'. Demonstrations showed that the ozonator gave the air of a room 'the impression of freshness' and removed the 'disagreeable odours or that sense of stuffiness' that sometimes characterised these areas (Anon, 1899: 525). Thomas Moffat, of ozone's biggest public health supporters, used ozone against cholera outbreaks in Newcastle. Taking a bottle with half a pint of water and a piece of phosphorous floating in it, Moffat placed this in a room and waited until the peculiar smell of ozone is detected', repeating the process up to three times a day (Moffatt, 1865: 303). Ozone's stimulant and germicidal effects were put to use in at least one military hospital during the First World War (Stoker, 1916: 712) and were also used for gas-warfare victims (Stoker, 1918: 550). However, trials of ozone applications for food and drink were often ambivalent. In 1901 experiments with different flasks of milk, including sterilised, unsterilised, and sterilized milk that had 'gone bad', it was found that passing ozone through them produced offensive odours in the first two cases but got rid of the smell of the bad milk in the final flask (Ransome and Foulerton, 1901: 61-2).
 
The growing interest in ozone also meant new ways of measuring its presence were developed. One of the issues with ozone was that, despite its smell being highly potent and easy to detect even in small amounts, it was often present in the air only in very diluted form. This meant that the nose was not always the best guide. In fact, correspondents recommending different ways of generating ozone in hospital rooms noted that if the gas was 'just sensible to the smell' then its concentration was already too great. The best level of ozone was that which was invisible to or only just appreciable by the sense of smell (Wise, 1887: 584). It was suggested that 'if ozone is used in a ventilating system… it should be in such concentration as is scarcely perceptible to a keen sense of smell' (Hill and Flack, 1911: 407). Visual tests were therefore developed to try and identify a substance that had taken its name from its smell. Schöbein developed a test using specially prepared papers which was then further developed by subsequent users. This involved soaking white blotting paper in a solution 1 part potassic iodide, 5 parts starch, and 100 parts of water. If ozone was present then a reaction with the paper would cause the iodine to be free and the starch to turn blue (Tidy, 1878: 62). In 1886 W. J. Black used ozone papers to compare the air of seaside towns, which coloured the paper and thereby proved the presence of ozone, with London's 'mephitic air', which bleached the papers white again (Black, 1886: 76). Similar experiments were conducted at sea, with papers hung upon the ship’s deck to observe the different levels of ozone in harbours, ports, and open sea (Black, 1885: 416). It was suggested that hill and valley meteorological stations in Britain might be equipped with papers for testing ozone, since this would enable conclusion about the 'purity and salburity' of the atmosphere (Wragge, 1880: 537). However, some still trusted the sense of smell over these visualisations. Leopold Gragenberg, the Goettinger Institute chemist, who had gained a PhD for research on ozone, argued that 'the identification of ozone through its odour is at least as reliable and precise as that by the iodine test, provided of course that the experimenter is used to the particular smell of ozone, and other odours are absent' (Vosamaer, 1916: 21).
Feelings and Noses
From the beginning it was suggested that what ozone did was alter the senses themselves rather than communicating a particular smell. In the early nineteenth century it had been suggested that the ozone was not the produce of a particular substance, but was instead the product of electricity acting on the olfactory nerves (Althaus, 1860: 103). The idea that ozone had a direct impact on the nerves was still being discussed in 1911. Rather than clearing the air of dangerous or discomforting impurities, ozone excited 'the olfactory nerves and those of the respiratory tract and skin' and thereby relieved 'the monotony of the close air, the smell of tube railways, in cold meat stores, hide stores, and other trades'. Ozone therefore had 'practice value in relieving the nervous system from the depressant influence of an unpleasant odour is none the less for this' (Hill and Flack, 1911: 408). Leonard Hill, one of the leading researchers working on ozone, suggested in a 1913 letter to The Times that it did not really matter whether ozone genuinely got rid of foul smells or simply stopped the person from being able to smell them. The 'smell of a tube railway' or a 'glue, soap, bone manure factory' or a 'cold meat, linoleum store, fried fish shop &c' was not poisonous but the evil smell 'depresses us by acting on our olfactory sense'. By taking away a 'monotonous and depressing sensation', ozone was doing a helpful job (Hill, 1913). Eric Keightley Rideal agreed. Given that most people also found the smell of ozone pleasant, it also provided a 'counter irritant to the olfactory organs' that was psychologically significant (Rideal, 1920: 155).

However, not everybody was convinced by this. The same accusations that had long been levelled against deodorizers and disinfectants were also hurled at ozone. Another writer to The Times suggested, ozone's capacity for masking bad odours should be used with caution: 'since bad odour are danger signals, anything which tends to conceal them is obviously not in the best interests of hygeine' (Anon, 1913). Ozone could neutralize the smell of stinking meat or human excrement, though of course 'the masking of these smells gives no proof of the destruction of the evil-smelling emanations' (Hill and Flack, 1911: 408). Further experiments on the physiological actions of ozone suggested that, in larger concentrations, its actions could be deleterious. Mice subjected to heavily ozonised air exhibited, one by one, slowed respiration, convulsions, and the death. Human exposure to ozonised air led to tightened chests, slower breathing, tingling skin, and a feebled pulse before experiments had to be stopped for worry about what might come next (Dewar and M’Kendrick, 1873: 104). Whilst humans were held to enjoy the smell of ozone, this was not thought to be the case for other animals. It was even suggested that ozone machines could be used for getting rid of vermin: 'In locks, channels etc the rats disappear immediately as soon as they perceive the smell of the disinfectant’ (Anon, 1908: 9).

By the end of the nineteenth century the belief in the health-preserving and -giving properties of ozone were widespread. The wide-ranging acceptance of ozone’s positive influence resulted in it becoming an advertising buzzword, so much so that in 1904 it was argued that 'there is a great deal of mischief in the use of the term ozone: all kinds of objects, perfumes and plants in the trade are supposed to produce a highly ozone-rich pleasure, judging by the advice given’ (Anon, 1904: 17). By the 1910s there were 'ozonators' on the market that depended on the oxidisation and evaporation of essential oils, such as cinammon oil. Such machines misled the public's noses, since they were 'supposed to believe that the odor they smell is ozone' (Vosamaer, 1916: 14). In this context, the gap between scientific descriptions of ozone and the wider application of the term by the public seemed to be gradually expanding.

But in some sense the seeds of this development had been established in the eighteenth century, when the first identification of the ‘electric odour’ had been through comparisons with weather phenomena and country air. In an 1889 lecture to the Leicester Literary and Philosophical Society, it was noted that 'the public often expressed much more decided opinions concerning ozone and its presence in the air than experienced chemists'. The speaker gave the example of a person who 'going fresh from the town into the country, went out in the morning upon the hills, and was full of satisfaction as he took deep inspirations, rejoicing at the thought that he was getting large quantities of ozone into his lungs' (Smithless, 1886: 478).

The domestic use of ozone provides another example. One did not have to turn to electric ozonators to generate some ozone for your home. Given that the 'peculiar odour that comes from freshly washed linen' when dried in the open air was due to ozone, 'you need only to hang up bed sheets in the house which have been damp for a long time and exposed to a sharp, dry wind; the air in the room is then filled with significant amounts of ozone'. It added that 'every housewife knows the strong, penetrating smell' (Anon, 1898: 6). Ozone’s hold on the popular mind was, at least in part, because it was easily perceptible to anybody who had smelled line-dried linen, thunder and lightning, or sea-side air. Despite the origins of the term in laboratory science and electrical experimentation, ozone’s olfactory reference points were embedded – even in Schönbein’s scientific descriptions - in ordinary, everyday, comparisons.
Creator:
William Tullett
Citation:
William Tullett, “Ozone,” Encyclopedia of Smell History and Heritage, accessed April 20, 2024, https://encyclopedia.odeuropa.eu/items/show/5.
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