Christian Friedrich Schoenbein to Faraday   26 October 1859

My dear Faraday,

My having spent the autumnal vacations partly at Neuchâtel, partly at Presinge the seat of our friend de la Rive on the frontiers of Savoy and returned to Basle but a few days ago, must excuse this late answer of mine to your last kind letter¹. Hard working had made such a temporary relaxation quite necessary to my mind. First of all, allow me to offer my most heartfelt congratulation to you on account of the celebration of your 68th birthday and let us hope, that it may please Him, who is the sovereign Lord of our life, to grant the return of many more. Generally speaking a long age is rather an equivocal gift and in the most favourable case accompanaied with many evils, which human flesh is heir to², amongst which not the slightest one is the feeling and consciousness that we have lost the bouyancy of Youth. But there are some privileged men, whose mind, in spite of carrying a heavy load of years upon their back, remain elastic and green, continuing to take the liveliest interest with every thing regarding the higher and nobler aims of Mankind. Either I am entirely mistaken, or you are such a man. May your body be a little broken down, your hairs have turned grey or white, your countenance be furrowed by wrinkles, perhaps even your walk and step somewhat tottering, what is that to you, who are still soaring in the highest regions of philosophy, whilst youngsters replete with bodily powers are crawling upon the lowest ground. A little more or less of memory, precious as this gift is, does not matter much and after all, according to what you have accomplished during your career of life, you are more than any other man entitled to enjoy the “otium cum dignitate”³. There is a german saying “Fünfzig Jahre Stillestand, sechzig Jahr fängt’s Alter an” and according to it, your friend must now also be called an old man, having the eighteenth of this month accomplished his sixtieth year. It is certainly with some reluctance that I acknowledge myself to be a “senex”, but my grey hairs give but too obvious an evidence in favor of the truth and I must submit to what I cannot change. Although far advanced in the career of life I nevertheless feel still rather youthly and have not yet lost to a perceptible degree my ancient love for science and philosophical research and that I consider as an invaluable boon received from him, who is the Giver of all good things, and as calculated to cheer up the evening of my life. Like you I have every reason to be most grateful to kind Providence for what fell to my lot, modest as it has been and not always made up of smiles and sunshine. But now enough of birthday reflections. During the summer gone by I have been rather active in my laboratory and trust my doings will not have been quite useless. Pray, listen now a little to my random talkings about philosophical matters. First of all know, that I continued to work upon what I have called “the chemical polarization of neutral Oxigen” of which subject I communicated you something in my last letter and from it you will recollect, that during the slow combustion of Phosphorus and Aether as well as the Electrolysis of water, both kinds of active Oxigen (<plus>O and <minus>O) make their appearance, the former in the shape of HO + <plus>O.

Having these many years considered the said slow combustion of phosphorus as the type of all the slow oxidations, which inorganic and organic bodies undergo in the moist atmospheric air or pure common oxigen, I suspected, that the peroxide of hydrogen might be produced, if not in all (from secondary reasons) at least in a great number of cases and directed therefore my attention first to the slow oxidation of the more readily oxidable metallic bodies. My conjecture proved correct, having already found out that half a dozen of metals during their slow oxidation give rise to the formation of very appreciable quantities of HO<2>, as you will perceive from the statements to follow. To ascertain with full certainty small quantities of that compound, I first wanted proper i.e. most delicate tests for HO<2> and I fully succeeded in finding out more than one of that description, in corroboration of which I may tell you, that by the means of them I am able to detect the millionth part of the said peroxide contained in water and even less than that. These tests depend upon the oxidizing and reducing effects produced by HO<2> upon certain substances. Dilute paste of starch containing some jodide of potassium, if it be mixt up with water containing but half a millionth of HO<2> is within a very short time colored dark blue on adding some drops of a weak dissolution of any protoxide salt of iron to the mixture. The dilute dissolution of HO<2> slightly acidulated by SO<3> discharges the red color of an acidulated dissolution of the permanganate of potash (by reducing the acid of that salt to the protoxide of manganese). HO<2> even in a most dilute state throws down prussian blue out of a mixture of most dilute dissolutions of the red cyanide of potassium and any peroxide salt of iron (by reducing Fe<2>O<3> to FeO). Most dilute HO<2> colored blue by some Indigo solution is rapidly discolored on adding some drops of a dilute solution of iron vitriol to the mixture. A dilute solution of chromic acid is certainly a less delicate test for HO<2>, than the mentioned ones are, but its property of being colored azureblue by water containing but 1/20 000 of HO<2> makes it in many cases a valuable and practical test, which I always use when I have to deal with water somewhat rich in HO<2>. Now by the means of those tests I have of late ascertained that during the slow oxidation of Zinc, Cadmium, Lead, Tin, Bismuthum and Copper (effected by moist common oxgyen or atmospheric air) perceptable quantities of HO<2> are always formed conjointly with the oxides of those metals. To produce HO<2>, some of the metals being in a state of mechanical division as Zinc, Cadmium and Lead, have but to be put in contact with pure water and atmospheric air for a very short time, but I find it more convenient to amalgamate first the metals with mercury. Take for instance 100 grammes of Zinc filings, and the same quantity of Mercury, put them into a tumbler filled with dilute sulphuric acid, stir up the metals by a glass rod and you will soon have a grossly powdered Amalgama. Now, after having that metallic mixture washed with water, put it loosely into a funnel, set upon a bottle, let a very thin vein of distilled water run over the amalgama, and by the means of dilute paste of starch containing Jodide of potassium, you will already detect peroxide of hydrogen in the water having passed (in the manner indicated) only once over the amalgama, if you add to a mixture of both some drops of a solution of Ironvitriol &c.- If you shake for a few seconds the said amalgama together with air and 100 grammes of distilled water, the latter will have the property of striking blue the paste of starch on adding to it a couple of drops of a dilute solution of any protoxide salt of iron. Water containing 1% of SO<3>, all circumstances being the same, produces more HO<2> than pure water does. You may satisfy yourself with one instance. Take 100 grammes of a still liquid amalgama of Lead, shake it with 100 grammes of the mentioned acidulated water and atmospheric air for 5 - 6 minutes, separate by filtering the sulfate formed from the water, add to the latter some drops of a dilute solution of Chromic acid and your liquid will be transiently turned azureblue, a proof of the presence of HO<2>. If you shake one volume of the said acidulated water, two volumes of pure Ether and some drops of a dilute solution of CrO<3> together, the ether assumes a still deeper blue color. The same acidulated water of course discharges the color of the permanganate solution &c. In saying so much about this matter, I must not omit to add that the quantity of HO<2> formed under the circumstances, reaches soon its maximum which does not go beyond 1/6000 of the quantity of acidulated water employed. The reason of this fact is obvious. I shall not enter into any more details about the subject, hoping to find soon an opportunity for sending you a paper containing all the particulars about this highly interesting formation of HO<2>⁴. From the facts above stated and others not mentioned I am led to conjecture, that all the slow oxidations taking place in the moist atmospheric air depend upon what I call “the chemical polarisation of neutral oxigen” i.e. that this act always precedes that of real oxidataion. The oxidable matter being eager to combine with <minus>O and water with <plus>O to produce HO + <plus>O, determine that mysterious polarisation of O in a similar manner as HO<2> is sometimes decomposed, if placed between two substances, one of which attracts the oxigen, the other the hydrogen of the compound. But be that as it may, perfectly sure is now the fact, that in a number of cases of slow oxidation the counterpart or antipode of <minus>O makes its appearance in the shape of HO + <plus>O and that the latter compound also acts an important part in those slow oxidations. I am inclined to suspect, that the chemical polarisation of O is deeply concerned in animal respiration and many other chemical actions going on in nature, but I will not yet talk about these matters. It seems that the late results of my researches tend to increase a little our insight in the workings of our chemical Hero, and you may therefore easily imagine, that I pursue my investigations on that really wonderful body with a zeal bordering upon mental excitement.

Mrs. Schoenbien and my children are, as to body, tolerably well, but the severe loss of our dearest Emilia still presses very heavily upon us all and most particularly upon the mind of my poor wife. That great physician Time has not yet healed much.

With the deepest regret I learn from you, that poor Miss Hornblower is far from having obtained the desired result from the painful operation she was obliged to undergo some months ago. Pray, remember me most kindly to her and express to the suffering Lady my fullest sympathy. It requires certainly an uncommon degree of moral strength and before all a most absolute submission to the will of God, to maintain herself in a tolerable condition of mind and spirits. Before closing my long letter, I ask you the favor to present my kindest regards to Mrs. Faraday, your Niece and relations, who were so very kind to my beloved daughter who is now no more.

Pray, don’t be too long in writing me and be assured, that every word coming from you is of the highest value to

Your | most attached friend | C.F. Schoenbein

Bâle Oct. 26. 1859.

Address: Doctor Michael Faraday | Royal Institution | Albemarle Street | London