Christian Friedrich Schoenbein to Faraday   17 September 1857

Bâsle Septbr. 17th 1857.

My dear Faraday,

The moment is fast approaching, which will separate my eldest daughter from her home, parents and friends, and as you may easily imagine, all of us, and Mrs. Schoenbein most particularly, are looking for that painful hour with feelings appropriate to the case. The girl herself, however, exhibits on that occasion more courage than I thought she could command and though being fully conscious of what she is about to undertake, the wicked woman does not seem to have lost any of her wonted spirits. If I were not fully convinced that my daughter should find a second home with your friend, I certainly would not have given my consent to her emigrating there; and, besides, my knowing, that you and Mrs. Faraday are near her, gives me confident hopes, that she will be well off in every respect and meet with good counsel as often as she will happen to stand in need of it. Pray be kind to the girl, for though my child, I am allowed to assure you, that she is a good and excellent creature, who, I have no doubt, will please you Mrs. Faraday and Miss Hornblower.

Within a month my second daughter Sophia, who by the bye was intended to be a philosopher, also will leave me to go to the far North and stay over the winter with some friends of mine at Altona. Though she will be placed in very good hands, still to be deprived of two daughters at once, who have these many years given so much life to our little domestic circle, is rather hard to their parents and younger sisters; but we cannot help and must suffer the girls to go their own way. To Mrs. Schoenbein those separatings will cost floods of tears in spite of her stoical maxims. In the course of this summer I have been travelling and working. I saw once more my favorite town “Nuremberg” that splendid and interesting monument of the middle ages, where every house, court and street puts you back to times and a state of things long gone by. At the same time I visited old intimate friends, (and that was the principal end of my journey) who thirty some years ago were my fellow students at the University of Erlangen. I need hardly tell you, that I enjoyed my trip very much and spent most delicious days with those old cronies of mine, one of whom happens to be one of the most extraordinary and amiable men, I know, being highly poetical, therefore full of imagination, rich of original ideas, of a matchless humor, teeming with wit and what I do not consider as the least of his many excellent qualities, full of the milk of human kindness, in short a genuine man every inch. In the little book which will be presented to you by Miss Schoenbein, the author has tried to depict the man in the chapter entitled “Der Freund”¹. Having once touched that “opusculum”, the authorship of which I leave you to guess, I beg you to accept that trifling as a keepsake. It is sort of “quodlibet” and hardly worth while to be read. But if you should feel inclined to know a little what curious notions a friend of your’s is entertaining on “Men and things”, get some chapters of the little work translated to you. I see that the author has taken the liberty to talk even of yourself, but have reason to think, that in doing so he was actuated by the most friendly motives.

I have continued my researches on oxigen, that inexhaustible source of investigation, and ascertained a series of novel facts which seem to be not altogether void of scientific interest. One of those facts is queer and paradoxical enough. What do you say to a desoxidation of an oxycompound being effected by the means of oxigen itself? You are perhaps aware, that some years ago I found out a number of substances enjoying the power to transform free <oring>O into O i.e to act like heat. The oxides of the precious metals and the metallic peroxides such as that of manganese, lead &c. belong to that category, and which are oxy-compounds containing either all or part of their oxygen in the ozonic condition. Now it appears, that the action taking place for instance between free <oring>O and PbO + <oring>O is reciprocal; for not only the former happens to be converted into O, but the peroxide of lead is at the same time reduced to PbO, which seems to show that the <oring>O of PbO + <oring>O also becomes desozonized and on that account eliminated. The same desoxidizing effect is produced upon PbO<2> by the ozonized oil of turpentine and the peroxide of hydrogen (to me = HO + <oring>O). To show those remarkable effects in a simple manner, I employ a test-paper being impregnated i.e. colored with minute quantities of peroxide of lead. If moist strips of that paper be suspended in strongly ozonized air, within a few hours they will be completely bleached i.e. PbO<2> reduced to PbO. The said test paper on being put in ozonized oil of turpentine or peroxide of hydrogen undergoes the same change. The strips joined will show you that effect. Now those curious facts seem to me to give room to a very strange conjecture, which, extraordinary and startling as it may sound, I cannot help communicating to you. I suspect that there are two kinds of active oxigen, standing to each other in the relation of algebraic magnitudes of contrary signs i.e. being such, as will neutralize each other into active oxigen, if brought together in equal quantities. Now supposing that there are three kinds of oxigen <oring+>O, <oring->O, O and assuming that HO<2> is = HO + <oring+>O and PbO<2> = PbO + <oring->O, those peroxides, on being brought in contact with one another, must be catalized, because the <oring+>O of the one neutralizes the <oring->O of the other peroxide into O, which as such can no more rest associated either with PbO or HO. For the reduction of PbO<2> to PbO being effected by free <oring>O, I am inclined to account in the same way i.e. by assuming opposite states of the two portions of oxigen, which act upon each other. In the two isomeric and crystallographically polar acids of Pasteur’s², which neutralize each other into what they call racemic acid³, we have a case of an analogous kind.

I am, of course, far from believing, that the fact above stated necessarily lead to such a conclusion, but for the present I cannot conceive any other hypothesis, by which the desoxidizing effect being produced by free <oring>O, ozonized oil of turpentine or peroxide of hydrogen upon PbO<2> could be better accounted for. Be that however as it may, as we philosophers cannot do and notably work without having some hypothetical views in our heads, I shall place myself for some time under the guidance of the conjecture alluded to and see what can be made out of it. If it leads me to the discovery of some interesting facts, I shall not feel ashamed of it, though it may turn out to be fallacious. We are no gods but shortsighted men and must be content with finding out a little bit of truth in wading through a sea of errors.

You know, it is an old notion of mine, that common oxigen as such cannot enter into any chemical combination and must undergo a change of condition i.e. become ozonized before it acquires oxidizing powers. The oxidation of phosphorus, oil of turpentine &c. being apparently effected by common oxigen is typical to me, because we know, and I think with sufficient certainty, that in those cases the ozonisation of common oxigen always precedes oxidation. In order to increase as much as possible the body of evidence speaking in favor of that assumption of mine, I have of late worked a good deal on the oil of bitter almonds (Benzule + H), which, as to its bearings to common oxigen, is certainly one of the most remarkable bodies, I know; for that oxigen being at the common temperature placed under the joint influence of the oil named and solar light, effects a number of oxidations, which only <oring>O but not O is capable of causing. Under the circumstances mentioned Jodine is eliminated from jodide of potassium, indigo solution discolored rapidly enough, the solution of guajacum blued, a great number of metals oxidized, even Silver not excepted &c. To convince yourself of that action in a simple way, add to dilute paste of starch, containing some jodide of potassium, a drop or two of hyduret of Benzule (free from prussic acid), shake in the dark that mixture together with ordinary oxigen, and no action will result; make the same experiment in the sun and the liquids will almost instantaneously be turned deep blue, just so as if free ozonized oxigen had acted upon the paste. The same color will make its appearance, if you treat in a similar way a recently prepared solution of guajacum. To show that even Silver is oxidized, put some drops of our oil upon a plate of pure silver and having the essence moved about in direct sunlight for a minute or two, aqueous sulphuretted hydrogen being poured upon the spot of reaction, will cause a rather abundant precipitation of sulphuret of silver, a proof of the presence of oxide of silver. I need not expressly state, that the hyduret of Benzule is oxidized along with the metals, in consequence of which benzoates are formed: benzoate of Lead, Cadmium, Copper, Silver &c. A very pretty experiment may be made with metallic Arsenic. Lay round a glass tube a ring of that metal (according to Marsh’s methode⁴) drop some oil of bitter almonds upon it, turn the tube being held in a horizontal position round its axis, no action in the dark, whilst in the direct solar light that ring will rapidly disappear under the circumstances indicated, arsenic acid being formed, just as is the case in ozonized oxigen. Rings of Antimony being not acted upon, or at least but very slightly under these circumstances, both the metals may be easily distinguished from each other by the means of hyduret of Benzule. The details of my researches on the oil of bitter almonds will be published by the academy of Munic⁵.

You know, that nitrification has been these many years a matter of interest and research to me and of late I have increased our knowledge about that subject by some novel facts. Some years ago, I found out, that ozonized oxigen transforms Ammonia into the nitrate of that base; last year I ascertained, that inactive oxigen on being put in contact with platinum or copper acquires the power of oxidizing even at the common temperature the elements of Ammonia into nitrous acid and water, nitrite of Ammonia being formed under these circumstances.

Now I have discovered that HO<2>, Mn<2>O<7> (permanganic acid) or the salts of that acid, for instance permanganate of potash, on being mixt up with aqueous Ammonia produce nitrites⁶. A singular fact is that free ozonized oxigen alone seems to be capable of oxidizing the nitrogen of Ammonia into nitric acid, the ozonized oxigen of oxy-compounds or the oxigen being rendered active by the influence of copper or platinum produces nitrous acid. Are we to infer from those facts, that the formation of a nitrite is the first stage of a nitrification?

One gambol more on my hobby-horse and I shall descend from the animal. I have of late succeeded in ozonizing the oil of turpentine so strongly that one equiv. of that essence is associated to one equiv. of oxigen, and you may easily imagine the great oxidizing power of that oil. By shaking it with peroxide of lead it becomes desozonized, PbO<2> being reduced to PbO, a fact, which according to the statements above made, is a matter of course.

Now you are released my dear Friend from listening to the talkings of a loquacious philosopher to whom, I hope, you will prove indulgent as you have already so often done him that favor.

Now nothing more than the request to remember me friendly to the most gracious She-Sovereign of the Royal Institution, whom you will beg in my name to take my girl under her high protection.

In hoping that you and Mrs. Faraday are doing well I am, my dear Friend

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

I must add a remark or two on my peroxide-testpaper. I prepare it by drenching strips of this filtering paper with a solution of PbO<2> and that solution is produced by shaking together (for about 15 minutes or so) two volumes of strongly ozonized oil of Turpentine and one volume of Extractum Saturni (subacetate of lead). On filtering that mixture I get a transparent liquid being colored like portwine which in fact is oil of turpentine holding some peroxide and oxide of lead dissolved. Upon the filter remains a yellow substance being a mixture of PbO<2> and PbO. Within 24 hours a similar mixture is deposited out of the colored essence. It is a remarkable fact, that the test-paper is rapidly bleached in strongly insolated atmosph. air, as you will see from a strip laid by, which in a good sun was completely bleached within an hour’s time. For that reason my test paper must be kept in the dark.