Christian Friedrich Schoenbein to Faraday   26 May 1855

My dear Faraday,

How could I employ the leisure hour of a fine May morning better and more agreeably than by devoting it to an epistolary conversation with my dear Friend Faraday, whom I besides owe an answer to his last amiable letter¹ and to-day, let me talk a little of Science.

As you cannot avert your mind from the contemplation of that mysterious agency called Magnetism, I am unable to let Oxigen out of sight and of late I have been actively working again on that curious subject not, I think, without some little success. You know that these many years I have entertained the notion according to which not only free but also Oxigen being chemically associated to some matter or other is capable of existing in two different conditions: in the common or inactive and the exalted or ozonic state and to distinguish by signs those different conditions from one another I have given to ozonised oxigen the symbol <oring>O denoting the inactive O by its usual sign = O. Considering the peroxides of hydrogen, nitrogen (hyponitric acid), Barium, Manganese, Lead &c as compounds containing both sorts of oxigen, I have given them the formula HO + <oring>O, NO2 + 2<oring>O, BaO + <oring>O, MnO + <oring>O, PbO + <oring>O &c and, as you are well aware, made these last six years many experiments with the view of separating from the oxycompounds mentioned and other similar ones their ozonised oxigen without obtaining however satisfactory results.

Some time ago Mr. Houzeau² communicated to the french academy a paper³, in which he suggested ideas on the different states of the oxigen being contained in compounds being exactly the same which I for the first time ventured to express in Poggendorffs Annals seven or eight years ago and have since more fully developed in the publications of the Phil. Society of Bâle, notably so in the last number of the proceedings of that learned body⁴. The views recently put up by Mr. Houzeau are therefore rather old acquaintances of mine, but that Chymist has ascertained a novel fact, and as I consider it, a very interesting one. On adding peroxide of Barium to the monohydrate of sulphuric acid he obtained oxigen enjoying all the properties of Ozone. I have arrived at the same end, but in a somewhat different manner. You know, Silver being exposed to the action of ozonised oxigen at the common temperature is transformed into the peroxide of that metal and you will recollect that I sent you a small quantity of that compound, some years ago⁵. Now it is from this peroxide of Silver which I consider to be Ag<oring>O⁶, that I succeeded to eliminate some Ozonised Oxigen.

On throwing the said peroxide into the monohydrate of sulphuric acid a most lively disengagement of a gaseous substance takes place conjointly with the formation of sulphate of Silver. The gas obtained in the manner indicated enjoys the following properties: its smell strongly resembles that of Ozone, but minute quantities being inhaled produce a sort of Asthma, as Ozone does; its electromotive power is strong; and like that of Ozone or chlorine, plates of Platinum or Gold becoming negatively polarised in the gas; it eliminates Jodine from the jodide of potassium and therefore turns instantaneously my test-paper dark blue, it rapidly transforms the yellow ferro-cyanuret of potassium even in its solid state into the red one; it suddenly oxidises sulphurous acid into sulphuric acid and sulphuret of lead into sulphate; it energetically and chlorinelike discharges the colors of organic matters such as Indigo, Litmus &c.; it colors blue the alkoholic solution of guajacum &c.

Now all these reactions being exactly those produced by Oxigen as modified by Electricity or phosphorus i.e Ozone I think, we may be allowed to conclude that the gas being disengaged out of the peroxide of Silver is, or contains, at least, the same principle i.e. Ozone.

Having but very minute quantities of that peroxide at my disposal, I, to my great regret, was forced to perform my experiments on a very small scale, but I had enough of the matter as to ascertain that the gas obtained was a mixture of <oring>O and O, in which the latter very much prevailed. Although there is no doubt to me that all the oxigen eliminated from the peroxide does in the moment of its being set free exist in the ozonic state, there are some obvious causes that account for the mixt nature of the gas i.e. for the transformation of <oring>O into O. One of them is the heat being disengaged at the points of contact between SO⁷ and AgO⁸ and the other the peroxide itself. As to the latter, you know perhaps that last year I ascertained the curious fact that a number of substances exert the same influence upon the ozonised oxigen as heat does i.e. destroy at the common temperature the ozonic condition of that oxigen without taking up a particle of it. The metallic peroxide enjoy that strange property in a very high degree and notably so that of silver, compounds as you see which to my opinion contain ozonized oxigen themselves. Now if a particle of peroxide of Silver not yet decomposed happens to come in contact with a particle of ozonised Oxigen being disengaged from another portion of the peroxide, that particle must become desozonised. There are perhaps some other causes unknown as yet that tend to change <oring>O into O in the case before us. I hope you still possess some of the peroxide of Silver I sent you some years ago and if so, you may even with that small quantity ascertain the correctness of my statements above made. In case you repeat my experiments I advise you to put a little peroxide into comparatively much Oil of Vitriol and do the thing at a low temperature from reasons that are obvious enough. To give you some visible proofs of the great chemical power of the oxigen having been eliminated from the peroxide of Silver by the means above indicated, I join three strips of paper one of them being impregnated with sulphuret of lead another with indigo solution, a third one with the coloring matter of litmus and you will perceive part of each of them to be bleached.

This was effected within a few instants by immersing a moistened end of the strip into the said oxigen.

From more than one reason I cannot help attaching some importance to the result of my experiments and believing that, if properly worked out and philosophically interpreted, it will lead to others of still greater consequence. And pray, let me reason and conjecture a little about it.

If it be allowed that the oxigen being contained in the peroxide of Silver exists in the ozonic condition and it being a fact that free <oring>O is by heat transformed into O, does it not appear very likely that the same agency has the power of changing the <oring>O of the peroxide into O and that this very change of condition is the proximate cause of the decomposition, which the peroxide undergoes when sufficiently heated? And if this conjecture should happen to be founded, are we not permitted to account in the same manner for the decomposition of all the other oxycompounds being effected by heat and yielding free inactive Oxigen? I am inclined to think that we are, and in a paper of mine printed last year I have given detailed reasons for entertaining such an idea. Now supposing my hypothesis to be true, I am afraid many of our present notions on the phenomena regarding chemical analysis, synthesis, affinities &c. cannot be maintained and must sooner or later be essentially modified. Stating that peroxide of Silver for instance consists of one Eq. of Silver and two Eq. of Oxigen and carbonic acid of one Eq. of Carbon and two Eq. of Oxigen is telling, if I may say so, but half the truth as regards the chemical constitution of the compounds named, for it implies the assertion that the oxigen being contained in those compounds is the same thing, an admission which according to my opinion cannot be allowed to be true, for <oring>O is not O though the one may be transformed into the other.

But if the oxigen being chemically associated to other matters be capable of existing in different states and the bearings of the oxycompounds be so much influenced by the peculiar condition in which their Oxigen exists in them, are we not permitted to suspect that other elementary matters may also enjoy a similar capacity of assuming different conditions and be able to exist within compounds in those various states? May it not be presumed that the chemical behaviour of such compounds essentially depends upon the peculiar condition of their constituent parts? Is it to be believed that carbon exists in the oil of turpentine exactly in the same state as it does in charcoal, and is it not possible that the decomposition of all the organic substances is effected by heat, because this agency has the power of transforming carbon from one state into another? To condense these questions and others that easily suggest themselves into one, I ask, is it not very likely that, what they call “allotropism” acts a much more important and general part in Chymistry than it is thought of as yet? I for my part think it to be so.

Now no more of Science, theories and such like! We descend to daily life and my family. Being all of us highly in love with nature we are very fond of rambling in fields and woods, on hills and dales to admire the unfathomable riches of beauties being displayed there. May is called in German “Wonnemonat” which means month of joy, and well meriting that poetical denomination, it is of course a favorite of ours and we indulge during its reign as often as we can in our rambling propensities by taking trips in the neighbouring country. The Jura mountains are a particular point of attraction to us with their rich woodland, limpid rivulets, green valleys, bold rocks and fine views. I preface thus to tell you that some days ago on a fine morning a motley army consisting of big and small Children, male and female and old folks too were seen marching out of the old gates of Bâle tending their steps towards the “Gempenstollen” the highest and most prominent point of the Jura in our neighbourhood. Mr. Schoenbein well acquainted with all the recesses and by-ways round about us, and his family making up good part of the army was unanimously elected commander in Chief which important charge he accepted and filled it up to the best of his powers. The day turned out a glorious one nature exhibiting all her charms. By a great and gradually rising round about way leading through meadows covered with flowers, green fields, flowering orchards, beautiful beechwoods crowded with singing birds we reached after a four hours walk the summit of our favorite hill. A little fatigued the army desired to camp here and it was allowed to do so. The delicately green foliage of fine beeches and the crowns of stately firtree formed a splendid canopy and the mossy ground yielded soft resting places. Carrying our victuals with us the dinner was soon ready and I can assure you that we enjoyed our cold morsels infinitely better than we should have done, had we sat down at a sumptuous royal table. Our camp being placed upon the top of a gigantic projecting rock it commanded a most extensive and glorious view <because> to the south at some distance, we saw the snowy heaventowering Alps of the Berner Oberland, nearer and to the west great part of the Vosges and Alsatia, to the north the Black Forest and Baden, nearest us the many valleys and summits of the Jura mountains. Being enchanted by that glorious sight we could not but most reluctantly break up our camp; but Mr. Schoenbein gave orders at last to march home again on a road however different from that we had come beautiful also beyond description. Having reached the foot of the hill the gypsy host was allowed to halt again for taking refreshments and by eight o’clock we approached the walls of the good town of Bâle, where the commander in chief discharged his troops not without having received before the thanks from high and low, old and young. I am sure you yourself and Mrs. Faraday would have highly relished the gypsy party but come over to us and we shall repeat it. Next midsummer we go to Langenbruck a village in some pass of the Jura intending to say there for a month. It would be a high treat to me and us all, if we could spend that time with you and Mrs. Faraday.

The gentleman who will deliver this letter to you is Mr. Schweitzer⁹ of Bâle an old pupil of mine and whom I take the liberty to recommend most friendly to your kindness.

Mr. Wiedemann charges me with his best compliments to you, he is very actively occupied with electrolytical researches and has received some interesting results.

Should a parcel be directed to you under my address, pray take and keep it untill you find an occasional conveyance for Bâle. There is no hurry for it.

Excuse my immoderately long letter, let me soon have the favor of a letter and believe me

Your’s | most truly | C.F. Schoenbein.

Bâle Mai 26th 1855.

Don’t forget to remember me friendly | to Mrs. Faraday.

Address: Doctor Michael Faraday | &c &c &c | Royal Institution | Albemarle-Street | London.