Christian Friedrich Schoenbein to Faraday   10 November 1856

Bâsle November 10. 1856.

My dear Faraday,

Many many thanks both for your own letter¹ and that of your Friend’s². When you happen to see her again, pray tell her that from many reasons my daughter desires to stay here during the winter. When spring comes and we live then, we shall see, whether a move over the water may be effected. In the mean while your friend will perhaps be kind enough to let you know her views on the subject in question. All I can say is this: Miss Schoenbein knows well and speaks fluently french and german and is considered to be a pretty good musician, in which accomplishments she is very willing to make herself useful in the establishment of your friend. As to the moral Character of my daughter, I am too partial to judge about, but I do not hesitate to qualify her as a modest, good natured and rather high-minded girl, and the purest Swabian blood running in her veins she partakes a little of the poetical spirit said to belong to the native land of her fore-fathers.

Since I wrote last³ to you I have actively continued my researches on the phenomena of contact, and obtained some results which are curious enough. You know perhaps that according to my former experiments ozonised oxigen at the common temperature oxidizes both the elements of Ammonia forming with that compound nitrate of Ammonia, whilst, as you are well aware, common oxygen does under the same circumstances not at all affect either gazeous or aqueous ammonia. The same oxigen however on being put in contact with certain matters acquires the power of engendering with ammonia nitrous acid i.e. nitrite of ammonia. Platinum and copper are such matters. Moisten the former metal (being in that state in which we call it “Ethiops”) with a strong solution of Ammonia, leave for a short time those substances exposed to the action either of common oxigen or atmospheric air, then treat the metallic powder with some distilled water and you will easily detect in that liquid the presence of nitrite of Ammonia. The simplest way of doing so it to put to that water some dilute sulphuric acid and paste of starch containing a little pure jodide of potassium (free even from the slightest trace of jodate). Nitrite being present the mixture will become dark blue.

Assisted a little by heat even compact platinum is capable of causing common oxigen to engender a nitrite with Ammonia. Put some drops of a strong solution of Ammonia into an air holding bottle introduce into the vessel the heated coil of a thick platinum wire, hold over that coil a strip of filtering paper to which sticks paste of starch containing some jodide of potassium and being acidulated by dilute sulphuric acid, and you will perceive that paste instantaneously turning dark blue. Whilst the hot platinum coil rests within the bottle, whitish vapours make their appearance which on being taken up by some distilled water give to that fluid all the properties of a nitrite solution. Being acidulated by dilute sulphuric acid it deeply and instantaneously blues the jodide holding paste of starch and such a strong reaction will be obtained though the heated coil may have remained in the bottle but for a few seconds. The platinum coil does not require being red heat to produce that effect, but those of iron wire &c: must have that temperature to enable oxigen to engender a nitrite with Ammonia. I above mentioned copper as another substance being capable of causing ordinary oxigen to oxidize both the elements of Ammonia at the common temperature, and I may add that its action even surpassed that of platinum. To convince yourself of the truth of my statement put about 50 grammes of minutely divided Copper (such as obtained from heated oxide of Copper by the means of hydrogen) into an oxigen or air holding bottle, moisten that metallic powder with a solution of Ammonia, close or cover the bottle and you will soon see filling the vessel with whitish fumes, which are nitrite of Ammonia; for if you introduce into the bottle a strip of paper being covered with acidulated paste of starch that contains some jodide of potassium, it will rapidly be colored blue. Or if suspended but for a short time strips of filtering paper being impregnated with distilled water, they will contain perceptible quantities of nitrite of Ammonia, as you may easily satisfy yourself by applying the test above mentioned. Even a moistened glassplate or watchglass, by which you cover the vessel of reaction will do to receive within a very few minutes so much of the nitrite formed as to enable you to ascertain its presence by the most striking reactions.

To complete my statements I must not omit to mention that the copper powder soon after having been moistened with liquid ammonia, exhibits a rise of temperature, no doubt resulting from the formation of the nitrate of ammonia. The blue liquid obtained on shaking copper powder with aqueous Ammonia and oxigen or atmospheric air besides oxide of copper also contains nitrite of Ammonia, for if you put some soda to it and boil it up to drive off the ammonia and throw down the black oxide of copper, a solution is obtained which after being evaporated to dryness leaves behind a yellowish salt being principally made up of nitrite of Soda. This substance being mixt up with powdered charcoal and heated burns that combustible matter, yields with sulphuric acid strong fumes of nitrous acid, rapidly discharges the colour of indigo solution being strongly acidulated by oil of Vitriol, colors brownish a solution of vitriol of iron containing free sulphuric acid &c. Common pure or atmospheric oxigen being put in contact with copper powder and aqueous ammonia is so rapidly taken up that I succeeded in depriving completely a whole cubic foot of atmospheric air of its oxigen within a few minutes. Copper and ammonia may therefore be used as eudiometric means and for preparing nitrogen from the common air. The facts above stated appear to me to bear closely upon the important question of nitrifications and proving beyond any doubt that under the influence of the contact of some ponderable matters inactive oxigen is empowered even at the common temperature to oxidize both the constituent parts of ammonia. Before long I hope to be able to give you some more details on nitrification, a chemical phenomenon which at this present moment deeply enjoys my attention.

Pray present my best compliments to Mrs. Faraday and believe me

My dear Faraday | Your’s most faithfully | C.F. Schoenbein.

Mrs. Schoenbein and the young ladies charge me to offer to you and Mrs. Faraday their kindest regards.

Address: Dr Michael Faraday | &c &c &c | Royal Institution | Albemarle Street | London