Christian Friedrich Schoenbein to Faraday   c. October 1848

My dear Faraday

To give you a sign of life I send you some lines through a former pupil of mine Mr. Burckhardt¹ of Bâle. In spite of all the revolutions and commotions which have taken place around us these last eight months² I have not given up my favorite researches and been rather industrious in my laboratory. Amongst other things I have made many experiments on the action exerted by Ozone upon metals at the common temperature and obtained pretty results. I have found out that with a few exceptions all metallic bodies are oxidized by Ozone to the highest degree they are capable of, Silver and Lead for instance being transformed at once into the peroxide of those metals, arsenic and antimony into arsenic and antimonic acid, without passing through their immediate degrees of oxidation. Though Silver be reputed to be much less oxidable than Copper, Zinc, Tin &c it is more rapidly oxidized by Ozone, than the metals mentioned. Polished plates of Silver Copper, Tin, Zinc being suspended within a strongly ozonized atmosphere are very differently acted upon. After half an hour's suspension the silverplate will have lost its metallic lustre and be covered with a layer of peroxide of Silver, whilst the plates of the other metals may remain for 24 hour's within our atmosphere without losing sensibly of there brilliancy. It may therefore be said that with regard to Ozone Silver is one of the most readily oxidable metals, provided silver and the other metals be exposed to the action of our oxidizing agent in the shape of compact and polished plates. Being in a state of minute mechanical division all the common metals silver of course included appear to take up the oxigen of ozone equally rapidly. The specimen laid by is a layer of peroxide of silver having been produced within 24 hours round a plate of very pure and highly polished silver. Arsenic and Antimony in the shape of brilliant metallic spots produced upon glass tubes or porcellain according to Marsh's method³ exhibit interesting bearings to Ozone. The arsenious spots are rapidly acted upon by Ozone and transformed into arsenic acid. 10-15 minutes are sufficient to make entirely disappear an arsenious spot when placed in air richly charged with ozone whilst a similar spot of antimony put under the same circumstances requires many days to loose its metallic lustre and be turned into the white hydrate of antimonic acid. I must not omit to state that Ozone produced by common electricity acts exactly upon the two kinds of spots like voltaic or chemical Ozone. With my rather poor electrical machine I succeeded in making entirely disappear a strong arsenious spot within 10-12 minutes, whilst a similar antimonious spot placed aside the former one and exposed at the same time to the action of the electrical brush was not yet sensibly affected and had retained all its metallic brilliancy. Ozone is therefore one of the means by which arsenic may be easily distinguished from antimony.

I think I have also succeeded in tracing out the cause of phosphorus being not able to produce ozone or (what is most intimately connected with it) undergo slow combustion in pure oxigen of the usual density and common temperature. The slow combustion of phosphorus being caused by Ozone it follows that all the circumstances which prevent or favor the generation of that oxidizing agent must also prevent or favor that slow combustion. Now a most essential condition of the production of ozone is a certain degree of rapidity of the evaporation of phosphorus; (only vaporous but not the solid phosphorus determines the formation of ozone) any physical circumstance facilitating the said evaporation favors therefore the generation of ozone or enlivens the slow combustion of phosphorus. In oxigen rarefied to a certain degree ozone is produced and phosphorus becoming luminous at the common temperature, and in common oxigen the same phenomena take place provided the temperature of the gas be raised by a certain number of degrees. Rarefaction or the heating of oxigen gas favors the evaporation of phosphorus and consequently the formation of ozone &c.

In Hydrogen and Nitrogen, having the same elasticity and temperature as oxigen, phosphorus evaporates more rapidly than in the last named gas and hence it comes, that in a mixture of hydrogen and oxigen, nitrogen and oxigen of the usual elasticity and temperature ozone is produced and phosphorous becoming luminous whilst in pure oxigen of the same temperature and elasticity the phenomena mentioned do not take place. I have circumstantially described my results in Poggendorff's Annals⁴ and I hope they will soon be published.

During the summer I made with my family a stay at a beautiful spot near the lake of Lucerne on the "Rotzberg" in the Canton of Unterwalden. We were very happy there and often said that our hill would be a place for our friend Faraday and his Lady. We led a truly dolce far niente life and my girls were jumping about in the hills like chamois. Confidently hoping you and Mrs. Faraday will enjoy at least tolerable health, I am my dear friend

Your's most truly | C.F. Schoenbein

Endorsed by Faraday: about Octr. 1848 perhaps