Julius Plücker to Faraday   18 June 1851

Dear Sir!

A longe time ago I got your last kind letter¹. Soon after receiving it I sent you “sous bande” the first two papers on the magnetic axes of cristals² (a third and last one is not yet finished). I paid them at the post office, but four months after I got them back, with the words “Rowland refused”. Newspapers are sent to England in the same way for a trifle of money. When there is a mistake, I would be angry if by my fault. You will get the papers now by a gentlemen returning to London. With pleasure I had brought them myself, in this time of the Exhibitions fever and the meetings of the British Association³; but I cannot leave Bonn befor[e] August.

I have joined to the papers a new metal, named Donarium (Do) discovered by professor Bergeman⁴ of Bonn⁵, thinking it may interest yourself and perhaps also the chemical section of the Association⁶. M. H Rose confirmed prof. Bergeman’s results. Fearing the reduced metal might be altered by crossing the Channel, he (B) prefers to present the hydrat of the oxyd (<chem1> + Aq.) You may reduce it easily, better by potassium or natrium than by hydrogenium. I give also a specimen of the mineral (Orangit), which is very rare, containing the new metal.-

Last su<bar>mer unhappily I did not succede in repeating E Becquerels experiments with oxigenium absorbed by charcoal⁷. At the same time I convinced myself that the results of my former experiments which induced me to admit the dilation of air in the neighbourhood of a magnetic pole, were illusorious. It may be proved mathematically, that there can be in such cases no sensible effect at all. In that desolate state of my head, regarding the magnetisme of the gases, I received with great satisfaction the first notice of your recent experiments with oxigenium⁸. I instantly undertook a long series of experiments, making use of a very fine balance of glass, indicating with full certainty 1/10000 of a gramme. In that way I may determine the magnetic power nearly with the same accuracy, then the weight of a body. I concluded first from my experiments that the specific magnetism of a body is a quantity as constant as the specific heat &c &c. The specific magnetism of oxigenium is exactly proportional to its density; it is not changed in a sensible way, when this gase is mixed with hydrogenium nitrogenium, carbonic oxyd, chlore &c &c. The specific magnetism of pure iron being 1000000, that of oxigenium is very near 3500. Hydrogenium, Chlore, Cyanic acid, carbonic oxyd, carbonic acid, <chem2> (protoxide d’azote) &c &c were not affected, the first one showing only a trace of diamagnetic action, but certainly not amounting to 1/200 of that on oxigenium.

Two months ago I sent two elaborate papers to Poggendorff but till now I got no copies of them⁹. Two weeks ago I sent a new paper¹⁰, schowing by experiment the coercitiv force of the gases, similar to that of steel.

By far the most curious and allways unexpected results presented Nitrogenium in its different combinations with oxigenium. I undertook about it a laborious series of experiments not yet quite finished. But I hope to overpower these days the last difficulty by condensing <chem3> (acide hyponitrique) in its purity. I expect the condensed gase will be strongly magnetic, as it is in its aëriform state. Then I shall be able to answer in a most accurate way one important question, by comparing the specific magnetism of the same substance in the two different states.

Within the narrow limits of a letter it seems to me rather impossible to give a true account of my researches. I’ll spare some of the results already obtained to a next co<bar>munication.

I hope your health be quite good now; with great satisfaction at least I may conclude it from what you worked in science. Tis only the impulse given by you, from which originates my recent researches.

With all my heart, Sir I am | Yours very truly | Plücker

Bonn, 18th of June | 1851.

Address: Professor Faraday | &c &c | London | Royal Institution