LIBRARY 
 
 UNIVERSITY OF CALIFORNIA. 
 
 Class 
 
THE LETTERS OF 
 BERZELIUS AND SCHONBEIN 
 
THE LETTERS 
 
 OP 
 
 JONS JAKOB BERZELIUS 
 
 At 
 
 AND 
 
 CHRISTIAN FRIEDRICH SCHONBEm 
 
 1836-1847 
 
 EDITED BY 
 
 GEOKG W. A. KAHLBAUM 
 
 BALE 
 TRANSLATED BY 
 
 FRANCIS V. DARBISHIRE, PH.D. 
 
 AND 
 
 N. V. SIDGWICK 
 
 WILLIAMS AND NORGATE 
 
 14 HENRIETTA STREET, COVENT GARDEN, LONDON 
 
 20 SOUTH FREDERICK STREET, EDINBURGH 
 
 AND 7 BROAD STREET, OXFORD 
 
 1900 
 
PRINTED BY 
 
 NEILL AND COMPANY, LIMITED 
 EDINBURGH 
 
 SENEKAi. 
 
EDITOR'S PREFACE 
 
 FOR some time past I have been engaged on the bio- 
 graphy of Christian Friedrich Schonbein, the discoverer 
 of ozone and the inventor of guncotton, formerly professor 
 of chemistry and physics at the University of Bale, the 
 hundredth anniversary of whose birth will be celebrated 
 on the 18th of October of next year. Schonbein's family 
 have assisted me in the kindest manner in this work; 
 they have placed at my disposal the whole mass of papers 
 which this indefatigable physical chemist left behind, 
 and the many hundreds of letters which he received. 
 
 Such writings, far more than the sifted published 
 results, give us a true insight into the thoughts of the 
 writer, and enable us to understand the workings of his 
 mind. We have, moreover, a never-failing series of 
 incidental allusions to the conditions, the manner and 
 the difficulties of sending letters, the calculation of the 
 cost of postage, and the time taken in travelling ; and 
 thus there develops almost insensibly before our eyes a 
 picture of a bygone age, which forms a background to 
 the image of the writer himself. We are continually 
 meeting with casual remarks, begotten of the confidence 
 of the moment, which reveal to us ever new traits of 
 character, and seem to bring the writer before us in person, 
 and to turn into tangible figures those who before were 
 to us often only names and shadows. 
 
 A 
 
 101714 
 
6 PREFACE 
 
 The letters which Schonbein left behind cover a period 
 of nearly fifty years. They begin in the year 1820 and 
 extend to his death in 1868. Among their writers are 
 to be found the most illustrious men of the time. The 
 greatest of all is Faraday : there are about seventy letters 
 from him to Schb'nbein, and as many more from Schonbein 
 in reply ; then come Grove, Graham, Sir John Herschel, 
 and a series of other English men of science. Among 
 Germans there is in the first place Wilhelm Eisenlohr of 
 Karlsruhe, the physicist, who furnishes more than a 
 hundred letters ; then Schelling, Schonbein's great teacher, 
 with whom he kept up a steady intercourse until his 
 death ; Liebig with fifty letters, and Pettenkof er with as 
 many more, and Wohler with about thirty ; then Martius, 
 Jolly, Kobell, Steinheil of Munich, Magnus, Mitscherlich, 
 and Poggendorff of Berlin, Erdmann of Leipsic, Muncke 
 of Heidelberg, Hugo Mohl of Tubingen, Dingier of 
 Augsburg, the well-known editor of the Polytechmcal 
 Journal, in whose factory young Schonbein had once 
 worked, and many others, particularly among his Swabian 
 countrymen. To these must be added a series of Swiss 
 scientific men : Auguste de la Rive, Marignac, Brunner, 
 and Agassiz ; while among Frenchmen we have Henri 
 Sainte-Claire-Deville, Dumas, Scoutetten of Metz, etc. 
 Finally there are nine letters extending from 1837 to 
 1847 from Jakob Berzelius. 
 
 The 9th of August of this year [1898] was the fiftieth 
 anniversary of the death of Berzelius, who was exactly 
 twenty years older than Schonbein, and died twenty years 
 before him. This anniversary, as is right, is not to be 
 allowed to pass unnoticed ; it is to be celebrated in Stock- 
 holm on the 9th of October, and I should be glad to be 
 able to assist in the celebration in some slight degree, by 
 laying the following pages as a modest tribute on the tomb 
 of the great master. 
 
PEEFACE 7 
 
 Prof. Henrik G. Soderbaum of Stockholm, a Fellow of 
 the Royal Swedish Academy of Sciences, has already 
 published at my suggestion, in the series of Monographs 
 on the History of Chemistry which I am editing, a 
 number dedicated to the memory of Berzelius, a subject 
 with which he is peculiarly fitted to deal ; but I should 
 wish to contribute my mite personally, by giving to the 
 public on the day of the celebration in Stockholm the 
 correspondence between Berzelius and Schonbein which 
 has been placed in my hands. 
 
 What I have to offer contains no startling novelties ; 
 no explanations that are to revolutionize our previous 
 theories can be derived from these letters. But to prove 
 what I have said of the importance of letters as the 
 original sources of the history of the development of 
 certain definite ideas, and of the knowledge of personalities 
 which we can derive from them, it is only necessary to 
 compare the letters which Berzelius wrote to Schonbein 
 with those which he wrote to Liebig \ for even these few 
 pages substantiate to the fullest extent the claims which 
 I have put forward. 
 
 And yet how wholly different were the lines of research 
 which the two men followed. Berzelius, a master of the 
 methods of quantitative analysis, has his attention always 
 centred on the final product, considered in its quantitative 
 relations : Schonbein, for whom this branch of chemical 
 research possesses hardly any interest, is far more bent on 
 acquiring from characteristic indications the means of 
 disentangling the course of the reactions. While Ber- 
 zelius' mind embraced the whole range of chemical know- 
 ledge, Schonbein concentrated his attention on a narrowly 
 contracted field, but yet regarded that field from com- 
 manding points of view ; and both took an equal interest 
 in observing the interconnection of chemical and electrical 
 energy. The younger man from the beginning looked up 
 
8 PKEFACE 
 
 with honest reverence to his great master in Stockholm, 
 while the latter, gradually convinced of the peculiar gifts 
 of his junior, ended by proclaiming with no uncertain 
 voice the importance of his investigations; the one, to 
 use Schonbein's own words, " with his ten talents gaining 
 ten more, while the other none the less strove to put his 
 single talent out at usury." These two men have filled 
 many a page in the history of our science, often with im- 
 perishable writings, and to these their letters serve as a 
 commentary. And I am grateful in no small degree to the 
 Royal Swedish Academy of Sciences at Stockholm, and to 
 their permanent secretary, Prof. G. Lindhagen, for their 
 great kindness and liberality in handing over to me for 
 publication the letters of Schonbein to Berzelius, which 
 are in the possession of the Academy, to which the letters 
 of Berzelius always have immediate reference. I was 
 thus enabled to do what is seldom possible in such a case, 
 namely, to give both sides of the correspondence at 
 once. 
 
 I trust that this little book will be favourably received ; 
 but at all events the two men whose words it contains 
 will secure for it a hearing. 
 
 GEORG W. A. KAHLBAUM. 
 
 STEINABAD, BLACK FOREST, 
 
 1st September 1898. 
 
NOTE BY THE TRANSLATORS, 
 
 WE have included in this translation two letters of 
 Schonbein's (of 12th February and 29th March 1847), 
 and also a paper of Schonbein's, "On various chemical 
 states of oxygen," which are not in the German edition. 
 They were discovered in January 1899 (after the latter 
 had been published), together with about 200 other 
 letters addressed to Berzelius, in the Berzelius Museum 
 at Stockholm, by Herr Lindstrom. They were placed 
 in the University Library at Bale for a time, in order 
 that we might obtain copies of them, and we wish to 
 express our thanks to the authorities of the Library 
 for their kindness in permitting us to do so. Schon- 
 bein's paper, which has never before appeared in print, 
 is of interest both generally and as throwing light on 
 the views which he expresses in his letters to Berzelius. 
 
 F. V. D. 
 
 1ST. V. S. 
 
OF THE 
 
 | UNIVERSITY '? 
 
 OF 
 
 CONTENTS. 
 
 PAGE 
 
 Editor's Preface, 5 
 
 Note by the Translators, ..... 9 
 
 I. Schonbein to Berzelius, 22nd April 1836, . . 18 
 
 II. Berzelius to Schonbein, 4th May 1837, ... 24 
 
 III. Schonbein to Berzelius, 14th October 1838, . . 28 
 
 IV. Berzelius to Schonbein, 13th November 1838, . . 32 
 V. Schonbein to Berzelius, 28th March 1839, . . 34 
 
 VI. Berzelius to Schonbein, 18th September 1840, . . 37 
 
 VII. Schonbein to Berzelius, llth September 1840, . . 39 
 
 VIII. Berzelius to Schonbein, 3rd November 1840, . . 42 
 
 ~tX. Schonbein to Berzelius, 23rd February 1844, . . 43 
 
 X. Schonbein to Berzelius, 14th April 1844, . . 45 
 
 XL Berzelius to Schonbein, 16th May 1844, . . 59 
 
 11. Schonbein to Berzelius, 15th January 1845, . . 62 
 
 XIII. Berzelius to Schonbein, 14th February 1845, . . 67 
 
 XIV. Schonbein to Berzelius, 1st March 1845, . . 69 
 XV. Schonbein to Berzelius, 22nd March 1845, . . 73 
 
12 CONTENTS 
 
 PAGE 
 
 XVI. Schonbein to Berzelius, 30th September 1845, . 79 
 
 XVII. Schonbein to Berzelius, 5th March 1846, . . 81 
 
 XVIII. Schonbein to Berzelius, 20th June 1846, . . 86 
 
 XIX. Berzelius to Schonbein, 18th November 1846, . 88 
 
 XX. Schonbein to Berzelius, 12th February 1847, . . 91 
 
 XXI. Berzelius to Schonbein, 12th March 1847, '. . 95 
 
 XXII. SchSnbein to Berzelius, 29th March 1847, . . 99 
 
 Appendix. On various chemical states of oxygen, 106 
 
THE LETTERS OF 
 
 BERZELIUS AND SCHONBEIN 
 
 SCHONBEIN spent the winter of 1827-28 in Paris, whither 
 he had gone like so many men of various nationalities 
 at that time to complete his studies. He had been a 
 science master in a school at Epsom and had acquired 
 a thorough knowledge of English. About this time a 
 French edition of Berzelius' Ldrbok i Kemien was pub- 
 lished. In an undated letter which I have before me 
 in draft only, but which was probably written in 
 November 1827, Schonbein writes to Koller, a friend 
 and countryman of his, who was a bookseller in London, 
 as follows : " Now as to a proposal which I have no 
 doubt you will accept. You are probably aware that 
 among chemists Berzelius is one of the leading lights of 
 the age, and that his textbook of chemistry, which, how- 
 ever, will not be completed before next year, is a classical 
 work. Three volumes have already appeared ; the fourth 
 and concluding one is expected soon. Now England 
 actually does not at present possess such a book ; and 
 since Berzelius is undoubtedly held in great esteem in 
 this country and his book is superior to any in Europe 
 in originality and exhaustive treatment of its subject, a 
 
14 LETTEES OF BEBZELIUS 
 
 friend of mine, an English chemist here, and I, thought 
 it would be well worth our while to undertake a transla- 
 tion of it into English. We are quite convinced that 
 such a publication would prove a financial success to the 
 publisher. Therefore I offer you the translation, and in 
 the event of your accepting it I enclose a brief announce- 
 ment which I think it would be desirable to print in some 
 widely-read paper, for the purpose of keeping others 
 from a similar undertaking and also of bringing it under 
 the notice of the public. Please let me know your final 
 decision by return of post, for, should you not feel inclined 
 to undertake it, we shall have to turn elsewhere. It is 
 no doubt an immense task, but by no means a hazardous 
 one, and certainly more profitable than the bookselling 
 business. 
 
 "My time is at present so taken up that I must 
 content myself with sending you my kindest regards. 
 C. E. S." 
 
 That Schonbein was really in earnest in his intention 
 of translating Berzelius' book into English is shown by 
 the fact that he enclosed an announcement of the proposed 
 translation for the daily papers. 
 
 We can also see what special object Schonbein had 
 in approaching so great a task. Sprung from humble 
 surroundings, he was forced to gain his own livelihood ; 
 and in addition to the strong liking he then had for 
 teaching, for which, however, he failed to find a promising 
 field in Paris, he devoted himself keenly to literary 
 pursuits. Thus, in November 1827, almost at the time 
 when he formed the project of translating Berzelius, he 
 wrote to Eriedrich Perthes of Gotha, with whom he was 
 already acquainted through his son and nephew, offering 
 to translate into German, from his shorthand notes, the 
 lectures on physics given by Gay-Lussac at the Sorbonne, 
 and to entrust them to him for publication. But this 
 
AND SCHONBEIN 15 
 
 and other works were comparatively unimportant enter- 
 prises, whereas the translating of the solid 200 sheets of 
 Berzelius' treatise, and moreover into English, a foreign 
 language, was certainly a stupendous task. 
 
 The motives which induced him to undertake so great 
 a work we learn from a letter, which I possess only as an 
 undated draft, which he wrote at about this time to his 
 friend and countryman Heldenmeier, who also was a 
 schoolmaster at Epsom. In this letter he declines for 
 the time being an offer to assist in founding a school in 
 his "beloved Switzerland," and writes respecting it as 
 follows : " Let me tell you why ; four weeks ago I formed 
 a fixed determination of [going] to Berzelius at Stockholm 
 towards the end of next [year ?] to complete my studies 
 under this consummate master of chemical science ; this 
 plan leads to others ; means must be procured for its real- 
 ization ; and it is a translation of Berzelius' unique work 
 that is to procure them ; a part of this work has already 
 appeared and the remainder is still in the press. With 
 this end in view I have joined with a young Englishman, 
 with whom I shall soon enter upon the work, which will 
 occupy us six months at the very least. So far we know 
 of no publisher, but we do not doubt that we shall be 
 able to find one, for the publication cannot be otherwise 
 than lucrative. Lee this, however, remain a secret 
 between us. I do not intend to return to England before 
 the lectures are over, for this would be foolish. Nor 
 shall I stay long. Should our plans be realized I shall 
 soon be sailing towards Sweden, where I propose to spend 
 at least six months. But after that . . . 1 " 
 
 Nothing came of the translation of Gay-Lussac's 
 lectures ; for Perthes wrote on December the 1st declining, 
 though in the most courteous terms, to publish them, 
 owing to other more pressing business, the details of 
 which he specifies; a similar fate befel the English 
 
16 LETTERS OF BERZELIUS 
 
 translation of Berzelius' textbook. The publisher could 
 not persuade himself to undertake the work, which, 
 though attended with a considerable outlay, would un- 
 questionably have resulted in pecuniary gain. The 
 consequence was that England had to dispense with a 
 translation of Berzelius' great and at that time unsurpassed 
 work, while Schonbein, foiled in his plan for obtaining 
 the necessary supplies, had to relinquish his scheme of 
 concluding his studies under " the consummate master 
 of chemical science." 
 
 It is no doubt an idle task to imagine what might have 
 happened if matters had fallen out otherwise; but we 
 cannot resist a feeling of the keenest regret that it was 
 not granted to Schonbein to turn his attention to quanti- 
 tative work as well under the influence of the powerful 
 personality of Berzelius, and our disappointment that a 
 publisher's lack of public spirit should have prevented 
 Schonbein from making this pilgrimage, is even more 
 acute than that caused by the events which hindered 
 Liebig from working under this great chemist's direction. 
 Berzelius and Schonbein were so unlike in character that 
 they could not but have been drawn together; and 
 Schonbein would have supplemented Berzelius far more 
 fully than Liebig would have done. Once again we 
 come across the name of Berzelius about this time in a 
 manuscript of Schonbein's. A small diary begun on the 
 21st of January 1828 in Paris, the last entry of which 
 dates from the 10th of March, gives us a clue to the 
 reading to which Schonbein devoted himself at this period. 
 A large part of this book, fifteen pages out of thirty, 
 is occupied by an abstract of Berzelius' paper on indigo. 1 
 It is evident therefore that Schonbein was not then 
 penetrated "by that almost unconquerable aversion to 
 
 1 "Recherches sur 1'Indigo," Annal. de Chimie^ vol. xxxvi. 
 (1827) pp. 310 and 350. 
 
AND SCHONBEIN 17 
 
 anything relating to organic life " which he confessed to 
 himself in later years. 1 
 
 It is quite typical, however, of Schonbein that this 
 paper of Berzelius' is preceded by a summary of a research 
 by Faraday 2 on the behaviour in vacuo of a crystal of 
 camphor, slightly cooled, as compared with that of 
 powdered camphor. 
 
 Not long afterwards negotiations were entered into 
 with Schonbein, who had just returned to England, 
 through Dr. Engelhart, 3 who was then living in Paris and 
 had refused a call to Bale, and they resulted in Schonbein 
 arriving at Bale in November 1828, and taking over, in 
 the first instance only provisionally, the professorship of 
 Peter Merian. 4 
 
 In 1835 and 1836 Schonbein delivered a course of 
 lectures before the Scientific Institute of Bale, 5 "which 
 for the most part treated of electro-chemical phenomena." 
 Among these his attention was particularly directed to 
 that behaviour of iron which he termed its passivity. A 
 summary of these communications appeared in Poggen- 
 dorff's Annalen, in the Bibliotheque Universelle and in 
 the Philosophical Magazine 6 : and it is thoroughly charac- 
 
 1 Schonbein, Menschen und Dinge. Mittheilungen aus dem 
 Reisetagebuch eines Naturforschers. Stuttgart und Hamburg 
 (1855) p. 117. 
 
 2 " On the existence of a limit to vaporization," Phil. Trans. 
 (1826) p. 484. 
 
 3 Johann Friedrich Philipp Engelhart, Ph.D., professor of 
 chemistry at the District Agricultural and Industrial School at 
 Nuremberg, was born in 1797 at Wildenstein, near Crailsheim, 
 in Wurtemberg, and died at Nuremberg in 1837. 
 
 4 Peter Merian, professor of physics and chemistry at Bale 
 from 1827 to 1835, born at Bale in 1795 and died in 1883. 
 
 5 "Bericht uber die Verliandlungen der Naturforschenden 
 Gesellschaft," in Bale, from August 1835 to July 1836. Part 2. 
 Bale (1836) p. 71. 
 
 6 Poggend. Annal, vol. xxxvii. pp. 390 and 590 ; vol. xxxviii. 
 
18 LETTEES OF BEEZELIUS 
 
 teristic of Schb'nbein that the report in the transactions 
 is not written by himself, but by his countryman and 
 friend Fischer, 1 professor of philosophy, in a paper 
 occupying twenty-six pages, entitled : " Account of Pro- 
 fessor Schonbein's experiments on the behaviour of iron 
 towards oxygen." 2 
 
 It is these experiments which form the subject of 
 Schonbein's first letter to Berzelius, dated 22nd of April 
 1836. The letter is as follows : 
 
 Schbnbein to Berzelius 
 
 BALE, 22nd April 1836. 
 
 DEAR SIR, 
 
 It is only your well-known kindness, and a 
 hope which I entertain that what I have to com- 
 municate may not be wholly without interest to you, 
 which encourage me, though a perfect stranger, to 
 trouble you with a letter from so great a distance. 
 
 For several months I have been occupied with the 
 more accurate determination of the behaviour of 
 certain metals, particularly iron, under various con- 
 ditions, in the presence of nitric acid. My work has 
 
 p. 444 ; [vol. xxxix. p. 137] (1836). Bibl univ., vol. iii. p. 
 387 ; vol. v. p. 177 (1836). Phil. Mag., vol. ix. pp. 53 and [259] 
 (1836). The passages in brackets were printed after the Bale 
 Keport. 
 
 1 Friedrich Fischer, professor of philosophy at Bale from 
 1832 to 1853, born in 1801 at Honau, Black Forest, in 
 Wurtemberg, and died in 1853 at Winnenden in the Neckar 
 district. 
 
 2 Easier Bericht, vol. i., part 2 (1836), p. 72. 
 
AND SCHONBEIN 19 
 
 not been altogether without results. I have observed 
 certain new phenomena which can hardly fail, 
 especially from an electro-chemical point of view, to 
 attract the attention of scientific chemists. They are 
 essentially as follows: If the end of an ordinary 
 iron wire of any size is heated in a spirit lamp until 
 its surface has become blue, and is then put in nitric 
 acid of specific gravity about 1/35, neither the heated 
 nor the other end of the wire is attacked. Indeed, 
 the acid can be heated almost to its boiling point 
 before it acts on the metal, although it attacks 
 ordinary iron even when cold. A similar behaviour 
 is shown by iron filings which have been heated only 
 for a few seconds, that is, until they have assumed a 
 blue colour. Now it is remarkable that the protec- 
 tive power of the heated end seems to extend through 
 any length of wire, however great. I took a wire 
 50 feet long and a line thick, heated one end for a 
 distance of not more than a few lines, and put first 
 this end and then the other into acid of the above- 
 mentioned strength. Under these circumstances no 
 part of the wire was attacked, even when its whole 
 length was allowed to lie in the acid. In order to 
 obtain a reaction it was necessary to heat the liquid 
 at least to 70. I performed similar experiments 
 with iron rods of a considerable size, and always 
 obtained the same result. Another remarkable fact 
 is this : An iron wire which has thus been protected 
 against the action of nitric acid can bring another 
 iron wire into the same neutral condition merely by 
 contact (which need only last for a moment, below 
 
20 LETTEES OF BEEZELIUS 
 
 the surface of the liquid). To convince yourself of 
 this extraordinary phenomenon, take an iron wire, 
 one end of which has been tempered by heating. 
 Bring the unheated end into close contact with one 
 end of another ordinary iron wire. If you now put 
 first the heated end of the first wire and then the 
 other end of the second wire into the acid, the latter 
 will not be attacked by it, even if the contact between 
 the two wires is destroyed. The second wire, having 
 thus become passive, can communicate the condition 
 to a third, and this to a fourth, and so on, provided 
 that the wires are brought into contact within the 
 liquid in the manner described. In order to prevent 
 any misunderstanding as to this second method of 
 rendering an iron wire inactive, I give a detailed 
 account of the way in which the experiment is to be 
 carried out. The ordinary wire, which has thus been 
 made indifferent to nitric acid, and which for the 
 sake of simplicity I will call " secondarily indifferent," 
 is taken out of the acid, and, at any point which has 
 not been immersed, brought into contact with another 
 iron wire. The end of the secondarily indifferent 
 wire is then placed in the acid ; and finally the end 
 of the other wire. Both wires now remain passive in 
 the liquid, always supposing that the temperature 
 does not rise above 70. For the sake of complete- 
 ness I must add that an iron wire which has been 
 immersed in nitric acid of specific gravity 1-5 is like- 
 wise indifferent to the acid of specific gravity 1'36. 
 A third phenomenon of interest is this : if an iron 
 wire, which has been made indifferent to nitric acid 
 
AND SCHONBEIN 21 
 
 in any of the ways described, is placed in the acid, it 
 is again attacked by it if brought into contact with 
 any metal, even iron itself, which is actually being 
 dissolved by the acid. The indifferent wire can, how- 
 ever, be made active even if the part projecting above 
 the liquid (which may be of any desired length) is 
 brought into contact with the similarly projecting 
 part of the active wire. For example in the accom- 
 panying figure 1 let a b be the vessel containing the 
 nitric acid, c d the indifferent, and e f the active wire. 
 If now the point c of the wire c d is brought into 
 contact with the point e of e /, the immersed portion 
 of c d at once becomes active, as also happens if / 
 touches d. The same thing occurs likewise if c is 
 connected with d by any metallic wire. 
 
 If the nitric acid is very dilute none of these 
 phenomena happen. After arriving at these results 
 I was curious to see how an iron wire would behave 
 in nitric acid if it was made the positive pole of a 
 voltaic circuit. My experiments on this point have 
 led to the following results. If the negative pole of 
 a cup apparatus of fifteen elements is connected with 
 nitric acid of specific gravity 1-35 by means of a 
 platinum wire, and one end of a common iron wire, 
 of which the other is attached to the positive pole, is 
 plunged in the acid, this wire remains perfectly in- 
 active and possesses generally all the properties of 
 the wires of which I have spoken above. Thus a 
 wire of this kind when separated from the positive 
 pole is not attacked by ordinary nitric acid. But if 
 1 There is no figure in the letter. 
 
22 LETTEES OF BEEZELIUS 
 
 the circuit is not closed exactly in the order I have 
 described, the nitric acid acts on the wire in the 
 usual chemical manner. If an iron wire which has 
 in any way been made indifferent is connected with 
 the negative pole of a battery, it is instantly attacked 
 by the acid with violence. But the most remarkable 
 fact of all, a fact which no one, so far as I know, has 
 ever observed, is this. The positive iron wire is not 
 only not- acted on~ky the acid, but it is not even 
 oxidized by the oxygen which is set free at its surface 
 by the decomposition of the water, which should 
 occur according to the accepted theory. The oxygen 
 appears as a gas on the iron just as it does on a wire 
 of silver or platinum, and the metallic surface is not 
 altered in the smallest degree. This liberation of 
 oxygen on the iron wire occurs in the most dilute as 
 well as in concentrated nitric acid, if, as I must once 
 more repeat, the circuit is closed exactly in the order 
 I have described. If you employ an acid of specific 
 gravity 1*36 diluted with ten times its volume of 
 water, and close the circuit, for example, with the 
 negative pole, not the smallest bubble of oxygen 
 appears on the iron wire forming the positive pole ; 
 on the contrary an iron salt is produced which sinks 
 down in yellowish-brown streams. The same occurs 
 even in acid diluted with 400 times its volume of 
 water. But if the end of the iron wire which has 
 been plunged in the acid is held only for a few 
 seconds in the air, and then the circuit is closed with 
 it, the oxygen again appears on its surface in the 
 gaseous form. If the iron terminal from which 
 
AND SCHONBEIN 23 
 
 oxygen is coining off is made to touch the negative 
 pole within the liquid for a few moments, the oxygen 
 no longer appears on its surface even when the two 
 wires are separated, the nitrate being produced in- 
 stead; but in this case also the iron resumes its 
 former indifference to the oxygen if it is held in the 
 air. I have measured the quantities of the gases 
 developed in the same time at the two poles and 
 found that the volume of the oxygen collected at the 
 positive iron electrode bears to that of the hydrogen 
 produced at the negative pole the ratio 1 : 2, which 
 may serve as a further proof that under these condi- 
 tions the iron is not in the least oxidized. Iron 
 placed under the same conditions in water to which 
 sulphuric or phosphoric acid has been added, likewise 
 develops oxygen gas ; but if the metal has previously 
 been placed in water containing sulphuric acid, or if 
 the circuit is closed with the negative pole, this 
 phenomenon does not occur. If the pole wires from 
 which the gases are coming off are made to touch for 
 a moment within the liquid, then, after they are 
 separated, no further development of oxygen takes 
 place, even if the iron wire is held for some time in 
 the air. In water containing potash, the oxygen 
 always appears in the free state on the iron, in what- 
 ever manner the circuit is closed. It is hardly 
 necessary to say that the iron must be the positive 
 pole. In order to bring to a conclusion a letter 
 which is already too long, I shall stop here and take 
 the liberty of drawing your attention to some papers 
 of mine, in which the phenomena I have described 
 
24 LETTERS OF BEEZELIUS 
 
 are treated in more detail, and which I hope will 
 soon appear in Poggendorff's Annalen. These pheno- 
 mena seem to me to be of the more importance in 
 that they do not agree with the electro-chemical 
 theory which is at present accepted. You have 
 already thrown light on so many of the dark places 
 of chemistry that I have no doubt you will also be 
 able to give a satisfactory solution of the problem 
 which my observations present. 
 
 Finally, I would once more ask you to pardon the 
 liberty I have 'taken ; and I beg to subscribe myself 
 with the utmost respect and esteem, 
 
 Your obedient servant, 
 
 Dr. SCHONBEIN, 
 Professor of Chemistry. 
 
 Berzelius answered in the following letter, which reached 
 Bale on the 15th of May 1837 : 
 
 II 
 Berzelius to Schonbein 
 
 STOCKHOLM, tth May 1837. 
 
 DEAR SIR, 
 
 There is an old proverb: Quod differtur, 
 aufertur. This might well be applied to my answer 
 to the letter with which you favoured me on 22nd 
 April 1836, and in which you communicated to me 
 your observations on the peculiar behaviour of iron 
 in the presence of nitric acid. I was away when the 
 
AND SCHONBEIK 25 
 
 letter arrived, and did not get home until it had 
 been awaiting me for some time, so I repeatedly put 
 off tendering you my thanks. The preparation of 
 my Jahresbericht for publication reminded me of it 
 once more, and so I now express to you my sincere 
 gratitude for the interesting information it contains. 
 In it you say that you wish me to give you my views on 
 the cause of these remarkable phenomena. I certainly 
 agree with you 1 that neither Faraday 2 nor Mousson 3 
 has suggested an acceptable theory. Indeed it would 
 seem hardly possible to decide what explanation is 
 the correct one ; but I maintain that a very likely 
 interpretation might be deduced from your experi- 
 ments, one which Faraday in fact has already 
 suggested in his last communication to the Editor of 
 the Philosophical Magazine] I mean the change of 
 electrical condition previously observed by de la 
 Eive 4 and Marianini, 5 a change which, at any rate in 
 metals, can be maintained for some time. It appears 
 that iron possesses a power as peculiar to itself as, 
 for example, its power of receiving magnetic polariza- 
 
 1 Berzelius is here referring to the following of Schonbein's 
 papers : " Bemerkungen iiber Faraday's Hypothese in Betreff 
 der Ursache der Passivitat des Eisens in Salpetersaure." 
 Poggend. AnnaL, vol. xxxix. (1836) p. 137 ; and " Die Unzulang- 
 lichkeit der bisherigen Hypothesen iiber die Passivitat des 
 Eisens," loc. cit., p. 342, which, however, was printed after 
 Schonbein's letter. 
 
 2 Phil. Mag., vol. ix. (1836) pp. 57 and 122. 
 
 3 Poggend. Annal., vol. xxxix. (1836) p. 330 ; and Bibl. 
 Univ., vol. v. (1836) p. 165. 
 
 4 Bibl. Univ., vol. iii. (1836) p. 375 ; and Mrfmoires de la Soc. 
 de Phys. et d'Histoire Nat. de Geneve, vol. vii. (1836) p. 457. 
 
 5 Annal. de Chimie et de Physique, vol. xlv. (1830) p. 113. 
 
26 LETTEES OF BEEZELIUS 
 
 tion, of passing from an electro-positive to an electro- 
 negative state, and remaining in this state under 
 suitable conditions, thus changing from an oxidizable 
 to a noble metal. If we admit this, the question 
 arises, What are the means by which this new 
 electrical state is produced ? Your experiments 
 indicate two distinct methods by which it can be 
 effected : in the first place by communicating to the 
 iron the electrical condition of some other body, for 
 example platinum, gold, concentrated nitric acid, 
 possibly also ferric oxide, and in the next place by 
 means of contact electricity, whereby a body with a 
 strong positive charge, such as the positive pole of 
 a battery or a solution of an alkaline hydrate, pro- 
 duces in the iron a charge of the opposite character. 
 But of course you cannot admit the latter assumption, 
 since you accept de la Kive's view that electricity of 
 an opposite character cannot be produced by contact. 1 
 In this, however, I do not agree with you; I am 
 firmly convinced that when we understand the cause 
 of this remarkable property of iron we shall find in 
 it one more proof that Volta's conception was more 
 profound and nearer the truth than that of his 
 opponents, who, by admitting that electricity and 
 chemical affinity are different manifestations of the 
 same force, acknowledge, though without being con- 
 scious of so doing, that Volta was right. 
 
 In the older papers 2 on the subject, ammonia also 
 
 1 Cf. Berzelius, Jahresbericht. Translated by "Wohler. Vol. 
 xvii. (1838) pp. 32 and 116. 
 
 2 Keir, Phil. Trans. (1790) p. 359 ; Wetzlar, Schweigger 
 
AND SCHONBEIN 27 
 
 is said to have the power of bringing iron into this 
 condition. It would be well worth while investigating 
 to what extent the other two magnetic metals, 
 nickel and cobalt, have this property ; even if they do 
 not possess it to the same degree, they may show 
 some indications of its existence. 1 
 
 I hope you do not intend to abandon this work 
 just yet ; it is conceivable that you may be able to 
 discover a method for making iron in any quantity 
 retain this condition for any length of time : such 
 a discovery would be of the highest value. 
 
 I have the honour to remain, 
 
 With the profoundest respect, 
 
 Yours obediently, 
 
 JAG. BERZELIUS. 
 
 In a letter, written in French, of the 12th of January 
 1838, Berzelius as permanent secretary of the Academy 
 acknowledges the receipt of the paper entitled : " The 
 behaviour of iron towards oxygen," 2 and to the printed 
 form adds a few words of thanks on his own behalf for 
 the copy sent to him personally. 
 
 The letter, however, contains nothing worth reprinting. 
 
 Jahrb., vol. xix. (1827) p. 470 ; vol. xx. (1827) pp. 88 and 129 ; 
 vol. xxv. (1829) p. 206 ; Fechner, ibid., vol. xxii. (1828) p. 27 ; 
 vol. xxiii. (1828) pp. 61, 129 and 429 ; vol. xxv. (1829) p. 223 ; 
 Fischer, Poggend. AnnaL, vol. vi. (1826) p. 43 ; Herschel, ibid.j 
 vol. xxxii. (1834) p. 211 ; cf. also Mousson, ibid., vol. xxxix. 
 (1836) p. 330. 
 
 1 Cf. Schonbein, Phil. Mag., vol. xi. (1837) p. 544 ; and 
 Poggend. Annal., vol. xliii. (1838) p. 18. 
 
 2 " Das Verhalten des Eisens zum Sauerstoff. Ein Beitrag zur 
 Erweiterung electro-chemischer Kenntnisse." Von Dr. L. [!] F. 
 Schonbein, Professor der Chemie in Basel. Basel, 1837. 
 
28 LETTEES OF BEEZELIUS 
 
 On October 14th of the same year, Sehonbein again 
 writes to Berzelius to report on his latest electro-chemical 
 investigations. 
 
 Ill 
 Sehonbein to Berzelius 
 
 DEAR SIR, 
 
 I trust you will forgive me for again taking 
 the liberty of troubling you with a letter, as it is only 
 scientific motives which induce me to write. In the 
 last few months I have spent a considerable time 
 on voltaic investigations, and have arrived at some 
 conclusions which seem to me not without importance 
 for electro-chemistry, and which I think you will be 
 interested to hear. 
 
 Becquerel asserts in his Traitt that wires forming 
 the poles of a circuit possess the power of pro- 
 ducing a secondary current only when they are in a 
 saline solution, and his view is that this current is 
 due to the re-combination, under suitable circum- 
 stances, of the base and the acid which have been 
 separated at the poles. The results of my latest 
 experiments render this theory untenable, for the 
 following reasons : 
 
 1. Chemically pure hydrochloric acid, sulphuric 
 acid, potash solution, etc., when used to complete the 
 circuit admit of electrical polarization of the elec- 
 trodes just as much as saline solutions. 
 
 2. Polarization of the electrodes occurs also when 
 the battery current which traverses them is too feeble 
 
AND SCHONBEIN 29 
 
 to effect electrolysis, when, for example, it cannot 
 decompose potassium iodide. 
 
 There is, however, another fact that I have dis- 
 covered, which I wish particularly to recommend to 
 your attention, and it is one which I think can 
 hardly fail to excite the interest of chemist and 
 physicist alike. It is the capacity which every 
 compound liquid conductor (electrolyte) possesses of 
 becoming electrically polarized. 
 
 The following facts will serve to bear out my 
 assertion. Fill a U-shaped tube with chemically 
 pure hydrochloric acid; put a platinum wire into 
 each limb, and connect these wires for a few seconds 
 with the poles of a battery whose current is too 
 feeble to produce on the electrodes the smallest trace 
 of gas. Now remove the wires from the tube, and 
 replace them by another pair of platinum wires which 
 have not been subjected to the action of a current ; 
 finally, connect these wires with a galvanometer of 
 several thousand turns. Under these circumstances 
 the needle of the galvanometer will be deflected in 
 such a direction as to indicate a current flowing from 
 the limb into which the negative electrode dipped to 
 that which was connected with the positive pole ; in 
 other words, the former limb of the tube behaves as 
 if it were positive to the latter. This fact makes it 
 obvious that the electrode and the column of liquid 
 directly in contact with it are both electrically 
 polarized at the same time and in the same sense by 
 the current which traverses them. As my work on 
 this subject will soon be published in Poggendorff's 
 
30 LETTEES OF BEEZELIUS 
 
 Annalen, 1 I will not enter into any further particulars 
 here, but will only say a few words on the apparent 
 cause of the polarization of liquids. 
 
 Since neither the voltaic nor the ordinary chemical 
 theory of galvanism is able to explain this strange 
 phenomenon, I have endeavoured to account for it 
 in the following manner. A current which is too 
 feeble to be able to decompose the hydrochloric acid 
 through which it passes still exerts some influence 
 upon it. In the first place it diminishes the mutual 
 affinity of the component parts of each molecule of 
 acid, though without actually separating them ; and 
 in the second place, such a current arranges all the 
 acid molecules so that their hydrogen is directed 
 towards the negative and their chlorine towards the 
 positive pole. Now, if we assume further that in 
 consequence of a certain inertia of the atoms this 
 condition of the acid does not disappear at once when 
 the current is interrupted, but that the constituent 
 parts of each molecule return only by degrees to 
 their previous condition of intimate connection, then 
 this act of re-combination of the hydrogen and chlorine 
 necessarily must, in accordance with the funda- 
 mental laws of electro-chemistry, produce a current 
 of exactly the kind which I have observed. That is 
 to say, the liquid column which was connected with 
 the negative pole must be positive to that which was 
 connected with the positive pole ; and this condition 
 of electrical polarization must continue until the 
 original equilibrium between the hydrogen and 
 1 Poggend. AnnaL, vol. xlvi. (1839) p. 109. 
 
AND SCHONBEIN 31 
 
 chlorine atoms has been restored throughout the 
 whole system of molecules. Now experiment has 
 shown that the current produced by the polarized acid 
 does as a fact last for a considerable time, as you will 
 find stated in the paper to which I have referred. 
 
 If my hypothesis ascribes the polarization in 
 question to its true cause, it must lead to the import- 
 ant conclusion for theoretical chemistry that between 
 the complete separation of two elements and their 
 most intimate chemical union there exist intermediate 
 conditions of combination, of which as yet we know 
 nothing ; unless indeed isomerism points to some such 
 relation. As you may readily conceive, I shall 
 devote my whole attention to a subject of such great 
 theoretical interest, and shall endeavour by pursuing 
 my investigations to throw still more light on the 
 question. If it were not too much presumption on 
 my part I would ask you to be so kind as to com- 
 municate to me at your leisure your views as to the 
 cause of the electrical polarization of liquid electro- 
 lytes. To a student of chemistry any suggestion 
 from so practised a master would be a cause of 
 gratification and encouragement. 
 
 In conclusion, I should be much obliged if you 
 would tell me whether the Eoyal Academy of 
 Stockholm receives papers in German, and, if so, 
 what formalities have to be observed. 
 
 I have the honour to remain, dear Sir, 
 Your most obedient servant, 
 
 C. F. SCHONBEIN. 
 
 BALE, Uth October 1838. 
 
32 LETTEKS OF BEKZELIUS 
 
 In a comparatively short time, that is to say in less 
 than a month, Schonbein received the following reply, 
 which reached Bale on the 25th of November. 
 
 IV 
 Berzelius to Schonbein 
 
 STOCKHOLM, I3th November 1838. 
 
 DEAK SIB, 
 
 I am greatly indebted to you for your 
 interesting communication of 14th October. 
 
 The polarization observed in the case of the so- 
 called liquid conductors is an experimental proof of 
 an assumption which, in my opinion, is quite essen- 
 tial to the theory of the electrical battery. I am 
 confident that it may be taken as proved beyond 
 a doubt that all substances, from the metals to the 
 worst conductors, as glass and resin, are capable of 
 assuming electric polarity, which will have a greater 
 tension and last the longer the greater their 
 resistance. This polarity is produced by every 
 disturbance of electric equilibrium, but the less 
 resistance a body has, the more rapidly does it dis- 
 appear, and the less is its tension. Hence the great 
 difficulty of actually exhibiting it in the case of good 
 conductors. But it is precisely this property of a 
 liquid or moist conductor on which the phenomena 
 of a hydro-electric pile depend, whether the initial 
 destruction of electrical equilibrium is due to contact 
 electricity or to chemical action ; and without it the 
 
AND SCHONBEIN 33 
 
 increase of tension in the poles of a battery when the 
 circuit is open would be inexplicable : for this tension, 
 generally speaking, is greater, the weaker the current 
 when the circuit is closed and the greater the resist- 
 ance of the liquid. Thirty-six years ago I put 
 forward as an experiment a theory of the galvanic 
 battery, which, however, no longer has much claim 
 to attention ; you will find it in Gehlen's Journal for 
 1803 or 1804. 1 In this theory I developed the view 
 that the state of polarization of a liquid conductor is 
 an essential condition of the difference of potential of 
 an electric battery, and it is still at the present time 
 my firm conviction that it is necessary to a right 
 understanding of hydro-electric phenomena. I main- 
 tain that you need not assume any special state of 
 combination in the liquid to explain its polarity, any 
 
 1 The date [1803 or 1804] points to: "Afhandling om 
 Galvanismen," Stockholm, 1802 ; however, he is probably 
 referring to : " Elektriska Stapelns Theori," Hisinger Afhandl. 
 i Fysik, vol. ii. (1802), which appeared in 1807, and was also 
 printed in Gehlen's Journal, vol. iii. (1807) p. 177. In the 
 early numbers of Gehlen's Neues allgemeines Journal der 
 Chemie, in 6 volumes [1803-1806], there is no such paper by 
 Berzelius ; on the other hand, there are some other papers, the 
 titles of which I will give here, as I failed to find them in 
 Poggendorff's Handworterbuch or in the Catalogue of Scientific 
 Papers of the Royal Society: 1. "Yersuch iiber die Farbung 
 der Thierknochen durch genossene Farberrothe," vol. iv. (1804) 
 p. 119. 2. "Uber die Zusammensetzung des Menschenkothes," 
 vol. vi. (1806) p. 510. 3. " tlber das oxidierte Stickgas, die 
 Thenard'sche Fettsaure, Flussspathsauregehalt des Zahn- 
 schmelzes," loc. cit. p. 590. Of the copy of Gehlen's Neues 
 allgemeines Journal, to which I had access, the 6th number of 
 the 4th volume was missing. I am therefore unacquainted 
 with its contents. 
 
34 LETTERS OF BEEZELIUS 
 
 more than in the resinous disk of the electrophorus, 
 which can receive a higher charge and retain it for 
 a very long time ; in fact, the power of becoming 
 polarized must be a fundamental property of all 
 bodies. 
 
 I have read with the greatest interest the papers 
 you published in Poggendorff's Annalen and in the 
 English Journals, and can only urge you to follow 
 up this important investigation. 
 
 With the profoundest respect, 
 Dear Sir, 
 
 Yours very truly, 
 
 JAC. BERZELIUS. 
 
 Schonbein to Berzelius 
 
 DEAR SIR, 
 
 I have taken the liberty of sending you the 
 last number of the Transactions of the Swiss 
 Association for the Advancement of Science, with 
 a humble request that you will give it a kindly 
 reception. 
 
 Though it does not contain much of great interest, 
 you will perhaps gather from it that the Swiss 
 have at least the wish to enlarge the boundary of 
 science. 
 
 The accompanying three numbers of the Eeport of 
 the work of the Scientific Club of this town are 
 intended for the Eoyal Academy, and as President of 
 
AND SCHONBEIN 35 
 
 that Club I request you to be so good as to forward 
 them to their destination. 
 
 I thank you most sincerely for your kindness in 
 answering the letter in which I had the honour to 
 inform you of my observations on the polarization of 
 water and other electrolytic liquids. In the course 
 of the last few months I have instituted a large 
 number of new experiments on this subject, and 
 have arrived at results which in my opinion give 
 a satisfactory explanation of the phenomenon. In 
 a paper which will, I hope, soon be published in 
 Poggendorff's Annalen, 1 I have described part of my 
 observations and have endeavoured to show that 
 electrolytic liquids are not capable of voltaic polariza- 
 tion in the proper sense, and that the current which 
 is produced by the so-called polarized bodies is due 
 to chemical action. I rely chiefly on the following 
 facts to prove the correctness of this view. An 
 aqueous solution of hydrogen (containing some 
 sulphuric acid to make it a better conductor) bears 
 the same electrical relation to an aqueous solution of 
 oxygen (also containing sulphuric acid), that the 
 liquid (water acidified with sulphuric acid) in one 
 limb of a U-tube, in which the negative pole of a 
 battery has been placed bears to the same liquid in 
 the other limb connected with the positive pole. 
 The two latter liquids only show themselves polarized 
 after the current has traversed them, if they are 
 connected with the circuit by means of platinum 
 wires and not if wires of gold or silver are employed. 
 1 Poggend. AnnaL, vol. xlvii. (1839) p. 101. 
 
36 LETTEES OF BEEZELIUS 
 
 This is exactly the behaviour of the two liquids first 
 mentioned, a solution of hydrogen and a solution of 
 oxygen or of ordinary atmospheric air. If the water 
 had been actually polarized by the current from the 
 battery, one would of course get a secondary current 
 whether the wires used to close the circuit were of 
 gold or platinum. I have given a detailed account 
 of this subject in several journals, 1 which you will 
 doubtless soon receive, and so it is unnecessary for 
 me to enter into particulars here; but I cannot 
 refrain from making the general remark that my 
 investigations appear to show that the act of 
 chemical combination of the elements is not due to 
 the play of electrical forces, or, in other words, that 
 affinity and electricity are not the same thing, 
 though they are mutually dependent. I am intend- 
 ing soon to develop these views of mine in a separate 
 treatise, and to establish their truth on experimental 
 grounds. 
 
 If I venture to express a doubt as to the truth of 
 the electro-chemical theory, it is in the conviction 
 that its founder would be the last man to blame me 
 for so doing, and I am sure that you will weigh the 
 arguments which I have to bring against it in a 
 spirit of the most perfect impartiality. You are too 
 much inspired by a pure love of science, and you 
 take too high a position in the scientific world, for 
 subordinate considerations to exercise any influence 
 on your judgment. 2 
 
 1 Journal fur prakt. Chemie, vol. xx. (1840) p. 129 [?]. 
 
 2 Cf. Poggend. Annal., vol. xlvi. (1839) p. 336. 
 
AND SCHONBEIN 37 
 
 I trust you will pardon my writing to you so 
 often, and with the greatest respect 
 I have the honour to be, 
 
 Dear Sir, 
 Your most obedient servant, 
 
 C. F. SCHONBEIN. 
 
 BALE, 28ta March 1839. 
 
 Berzelius replied somewhat briefly to this letter. If, in 
 fact, though I am not quite certain about it, the passage 
 in Schbnbein's letter refers to his brief summary in vol. 
 xx. of the Journal fur praktische Chemie, which how- 
 ever was not printed till 1840, he rejects Schonbein's 
 interpretation with the following curt and severe comment : 
 "Even these outlines show that Schonbein has not 
 grasped the spirit of the electro-chemical theory." 1 I 
 imagine that the following letter of Berzelius relates to 
 this paper of Schonbein's, because in the Jahresbericht, 
 vol. xxi., it is discussed simultaneously with the paper of 
 Faraday's mentioned below. 
 
 VI 
 Berzelius to Schonbein 
 
 STOCKHOLM, 18th September 1840 
 
 The permanent secretary of the Academy to 
 Professor Schonbein, Bale. 
 
 The Academy has received your three treatises, 
 entitled, "Bericht iiber die Verhandlungen der 
 
 1 Jahreslericht, vol. xxi. (1842) p. 33. 
 
38 LETTERS OF BERZELIUS 
 
 Naturf orschenden Gesellschaf t in Basel," also, " Mittel 
 und Hauptresultate aus meteorologischen Beobacht- 
 ungen in Basel," by Peter Merian, which you were 
 kind enough to send to it. I am instructed to 
 express to you their gratitude. The papers have 
 been deposited in the library of the Academy. With 
 the assurance of my utmost regard, 
 
 I have the honour, Sir, to remain, 
 
 Your very humble servant, 
 
 JAC. BEEZELIUS. 
 
 P.S. I must thank you on my own behalf for the 
 number of the Transactions of the Swiss Association 
 for the Advancement of Science of their meeting at 
 Bale in 1838, which you were kind enough to send 
 me, and also for the very friendly letter, in which 
 you stated the reasons which induced you to ascribe 
 hydroelectric phenomena to the play of chemical 
 affinities. This is also the opinion which Mr. Faraday 
 arrived at after his long series of researches on the 
 subject 1 ; and it certainly is the opinion which 
 suggests itself at first sight. I dare say you are 
 aware that I do not adhere to it, and I am always 
 waiting for some of the physicists who hold the so- 
 called chemical theory to explain by this hypothesis 
 in a satisfactory manner the chemical phenomena 
 brought about by the electric current, as for example 
 the reduction of potash ; for a theory which fails 
 to give any distinct or logical explanation of the 
 chemical decompositions produced by the electrical 
 
 1 Phil. Mag., i. 16 (1840) p. 336. 
 
AND SCHONBEIN 39 
 
 current cannot be the true theory of the electric 
 battery or of the cause which renders it active. On 
 the other hand the contact theory, according to which 
 chemical affinities depend on the electrical state and 
 not vice versa, adequately explain the chemical 
 phenomena which the battery produces. 
 
 VII 
 Schbnbein to Berzelius 
 
 DEAR SIR, 
 
 I take the liberty of sending you, by favour 
 of Herr Schiitz of Summiswald, a paper 1 which you 
 have probably not yet seen, and whose contents will, 
 I think, not be wholly without interest to you. 
 Unfortunately, the accumulation of business has 
 prevented me from following up further the subject 
 which is there discussed ; and I have not had time 
 to prepare the odoriferous principle (which I may 
 mention that I have called ozone) in sufficiently 
 large quantities to be able to determine its chemical 
 properties accurately. As soon as I have the necessary 
 leisure I shall proceed at once to continue this 
 work, and shall in due time make the scientific 
 
 1 The reference is probably to the paper: " Beobachtungen liber 
 den bei der Electrolysation des Wassers und dem Ausstromen 
 der gewohnlichen Elektricitat aus Spitzen sich entwickelnden 
 Geruch." Which edition is meant, whether AWiandl. der 
 Milnchner AJcademie, iii. 257, or Poggendorff, 50, 616, 1 cannot 
 say. In the Jahresbericht, xxi. (1842) p. 39, Berzelius refers to 
 the Annalen. 
 
40 LETTEES OF BEKZELIUS 
 
 public acquainted with the results of my investiga- 
 tions. 
 
 Meanwhile I have practically proved that ozone 
 plays an important part in the so-called voltaic 
 polarization of water, and that it is the cause, for 
 example, of the negativity of that portion of the 
 acidified water in which the positive pole of a battery 
 has been placed. 
 
 I should be excessively obliged if you would take 
 an opportunity of letting me know what you think 
 of the conclusions which I have drawn from my 
 experiments. 
 
 Is it not possible that we might sometime have 
 the honour and pleasure of welcoming you in 
 Switzerland? I do not think you would find our 
 country otherwise than agreeable. I have for a 
 long time had a great desire to see your interesting 
 country, but 1 having got a wife and nearly half a 
 dozen of children I am nailed down to a spot and 
 cannot think of moving much about. 
 
 With the greatest respect, I have the honour to be, 
 
 Dear Sir, 
 Your most obedient servant, 
 
 C. F. SCHONBEIN. 
 
 BALE, llth September 1840. 
 
 I do not possess the original of Berzelius' answer to this 
 letter, in which Schonbein gave the first information of the 
 discovery of ozone, but only a copy (expressly described 
 as such) in Schb'nbein's own hand. In April "1840 
 
 1 [The rest of this sentence is in English in the original. Tr.] 
 
AND SCHONBEIN 41 
 
 Schonbein had sent his first paper : " Uber die materielle 
 Ursache der Geruchsempfindung bei Elektricitats-Ent- 
 wickelung " in manuscript with a letter to Schelling 1 at 
 Munich. In his answer on the 24th of April of the 
 same year Schelling speaks in the highest terms of the 
 research, which he had immediately passed round among 
 the members of the mathematical and physical class of the 
 Royal Academy ; and particularly requests Schonbein to 
 allow them to print it in their Transactions, " to which it 
 would certainly do credit." He continues as follows : 
 " Steinheil 2 dabbles in many things without obtaining any 
 results ; he receives 80 a year for prosecuting researches 
 which, however, invariably break down without leading 
 to any conclusions. In the person of our Crown Prince 3 
 we possess a distinguished patron of research, especially 
 on scientific lines. Should you ever be unable from want 
 of pecuniary resources to begin a lengthy research, from 
 which you have grounds for expecting good results, let me 
 know and it will give me great pleasure to awaken the 
 interest of our generous prince on your behalf." 
 
 Schonbein consequently sent in an application to the 
 Prince through Schelling for a sum of money to purchase 
 a battery ; but as this appeal coincided with the former's 
 departure for Greece, the matter could not then be 
 arranged. Schelling writes on the 21st of December 
 1840 : "I am sure the Prince will not allow the matter to 
 
 1 Friedrich Wilhelm Joseph Schelling, born in 1775 at Leon- 
 berg in Wurtemberg, was professor at Jena in 1798, at Wiirz- 
 burg in 1803, member of the Munich Academy from 1806 to 
 1820, then at Erlangen ; in 1827 he was professor at Munich, in 
 1840 at Berlin, and he died in 1854 at Ragaz. 
 
 2 Karl August Steinheil was born in 1801 at Rappoltsweiler 
 in Alsace, and died in 1870 at Munich. From 1832 to 1849 he 
 was professor of physics and mathematics, from 1835 an ordin- 
 ary member of the Academy at Munich. 
 
 3 Subsequently King Maximilian II. 
 
42 LETTEES OF BEKZELIUS 
 
 drop, and I also shall not fail, whenever I have a con- 
 venient opportunity, to remind him of it. I regret to 
 say, however, that the Prince has taken all the documents 
 and also your note to Berzelius along with him." 
 
 Schonbein had in fact enclosed, as a recommendation, 
 Berzelius' letter to him on the discovery of ozone. Prince 
 Maximilian never returned it, but Schonbein had prudently 
 retained a copy. 
 
 VIII 
 Berzelius to Schonbein 1 
 
 STOCKHOLM, 3rd November 1840. 
 
 DEAK SIR, 
 
 I thank you sincerely for your paper on ozone, 
 and the courteous letter which accompanied it. I 
 read it with great interest, and consider it highly 
 probable, as you suggest, that natural waters con- 
 tain, though in very minute quantities, some volatile 
 matter, composed possibly of hydrogen and ozone. 
 The building up of this body in some conclusive 
 manner would be one of the most brilliant chemical 
 discoveries ever achieved by science. I need hardly 
 urge you not to let the matter drop before you are 
 successful, however great an exertion be required. It 
 is quite probable that water is always accompanied 
 by this compound in nature, for we know that common 
 salt never occurs in nature without traces of sodium 
 iodide or sodium bromide. 
 
 1 This letter is mentioned in Hagenbach's obituary notice of 
 Schonbein. [Basel Universitats-Programm, 1868.] 
 
AND SCHONBEIN 43 
 
 In former times I noticed that whenever I per- 
 formed electrical experiments for some time continu- 
 ously, for which purpose I employed a very powerful 
 battery, the whole atmosphere of my room smelt of 
 phosphorus for hours afterwards. I was convinced 
 that this could not result from the action of electricity 
 on the organs of smell, since it continued even after 
 the disengagement of electricity had ceased ; but it 
 seemed impossible to determine how it originated. 
 I hope you will let me know what results you obtain 
 by continuing these experiments. 
 
 With the greatest respect, 
 
 Yours most obediently, 
 
 JAC. BEEZELIUS. 
 
 IX 
 Schonbein to Berzelius 
 
 MY DEAR BARON, 
 
 I take the liberty of sending you a little 
 work 1 that has just appeared, in which I have dis- 
 cussed some physico-chemical questions. As you 
 will see from its contents, the views which I have 
 developed as to the relation between voltaism and 
 chemism differ in important respects from those of 
 
 1 He refers to the book dated December 1843, and dedicated 
 to A. de la Rive, entitled, Beitrage zur Pliysikalisclien Chemie, 
 Basel, 1844. It is divided into three parts : (1) On the fre- 
 quency of contact- action in chemistry. (2) On the cause of 
 increase of conductivity of water by means of acids, alkalis and 
 salts. (3) On the action of hydro-electric currents. 
 
44 LETTEES OF BEEZELIUS 
 
 Faraday and de la Eive ; but I hope that this will 
 not prevent my work from contributing something 
 towards the agreement of physicists on a question 
 which has so long been the subject of controversy. 
 In the second part of the book I have given some 
 conjectures as to the chemical constitution of the so- 
 called hydrated acids and bases, as well as of many 
 double salts. I am really very curious to hear what 
 you think of the hypotheses which I have pro- 
 pounded, and you would be doing me the greatest 
 kindness if you would take an opportunity of letting 
 me know in a letter what is your frank opinion of 
 them, and also of the contents of the first section, 
 dealing with contact action. I have been much 
 interested to learn, from a communication l of yours 
 to the Stockholm Academy, that you are inclined to 
 ascribe the passivity of iron to an allotropic condi- 
 tion of the metal. The only remarkable thing about 
 it is that the allotropy should be confined to the 
 surface, and not extend in any degree to the interior 
 of the iron; for the current which determines the 
 passivity of the surface goes through every part of 
 the iron, which serves as positive electrode. The 
 statements which Martens of Brussels has quite 
 recently made to the Academy of that town, 2 accord- 
 ing to which a red heat, irrespective of any oxidation, 
 is sufficient to secure the passivity of iron, are quite 
 
 1 Stockholm Acad. Handl. (1843) p. 1 ; and Poggend. Annal., 
 vol. Ixi. (1844) p. 14. 
 
 2 Bruxelles Acad. Sci. Bui (1843) [Pt. 2] p. 406 ; [Supple- 
 ment in Poggend. AnnaL, vol. Ixi. (1844) p. 121]. 
 
AND SCHONBEIN 45 
 
 without foundation, as I have convinced myself by 
 repeated experiments. 
 
 With the greatest respect and esteem, 
 
 I have the honour to be, my dear Baron, 
 Yours most sincerely, 
 
 C. F. SCHONBEIN. 
 
 BALE, 23rd February 1844. 
 
 Berzelius made no answer to this letter of Schonbein's, 
 nor does the Jaliresberwlit contain any references to these 
 questions or to the book on physical chemistry forwarded 
 to Berzelius. 
 
 X 
 Schonbein to Berzelius 
 
 BALE, \th April 1844. 
 
 MY DEAR BARON, 
 
 You were formerly interested in my experi- 
 ments on the nature of the electrical odour, and so I 
 natter myself that the results of my latest work l on 
 this subject will not be wholly indifferent to you, more 
 especially as they seemed to you to have opened a 
 new field for chemical investigation. You will re- 
 member, no doubt, that I endeavoured to prove the 
 
 1 Lectures delivered at meetings of the Association for the 
 Advancement of Science at Bale on the 3rd and 17th of April 
 and the 15th of May 1844 : Easier Berichte, vol. vi. (1844) p. 16. 
 Bibl. Univ., vol. 1. (1844) p. 395 ; collected in " tjber die 
 Erzeugung des Ozons auf chemiscliem Wege," Basel, 1844. Pre- 
 face dated 13th May 1844. 
 
46 LETTEES OF BEKZELIUS 
 
 chemical identity of the substance produced by the 
 electrical discharge in the air and that formed in the 
 electrolysis of water from the similarity of their 
 voltaic properties ; and that the electric character of 
 my ozone together with its chemical behaviour led 
 me to conjecture that it was a body very similar to 
 chlorine. Quite recently I have succeeded (at least 
 I think I have) not only in showing by a satisfactory 
 proof that the two odoriferous principles are identical, 
 but also in preparing the substance by a chemical 
 method, and that in such quantities that I have 
 every reason to hope that I shall be able to isolate it. 
 The identity and the haloid character of the body 
 produced under such different conditions are shown : 
 1. By the complete similarity of the smell of chemical, 
 voltaic and electrical ozone. 2. By the remarkably 
 strong negative polarization produced by these three 
 substances. 3. By the destruction of its smell and of 
 its polarity by all bodies which take up or combine 
 chemically with chlorine ; for example, easily oxidized 
 metals, stannous chloride, ferrous chloride, ferrous 
 sulphate, alkaline solutions, etc. 4. By its power of 
 destroying vegetable colours with great energy. 5. 
 By its power of instantly decomposing potassium 
 iodide and setting iodine free ; of turning potassium 
 ferrocyanide into ferricyanide ; of breaking up 
 hydrogen sulphide, hydrogen selenide, etc. ; of con- 
 verting sulphurous into sulphuric acid in the presence 
 of water, thus decomposing water under exactly the 
 same conditions as chlorine ; and of being destroyed 
 by ammonia. I might mention yet more chemical 
 
AND SCHONBEIN 47 
 
 facts which all go to establish, in the most satisfactory 
 manner, the analogy between chlorine and my 
 ozone. 
 
 I have no doubt that you will be astonished when 
 I tell you how ozone can be produced chemically, for 
 the conditions of its formation are such as would not 
 lead one to expect in the remotest degree the results 
 which are actually obtained. The method is this: 
 Commercial phosphorus is allowed to stand in a flask 
 filled with atmospheric air. If the temperature of the 
 experiment is only a few degrees above zero, the air 
 above the phosphorus somewhat rapidly assumes a 
 positive potential, that is, it has the power of polar- 
 izing positively a strip of gold-leaf held in it. If the 
 temperature is not raised in any way the air remains 
 in this voltaic condition and smells of phosphorus, 
 i.e., like garlic. But if the air is warmed to 8-12 
 its positive potential changes rapidly to the opposite ; 
 that is, it assumes the power of polarizing a gold-leaf 
 negatively. This change of the electrical condition is 
 accompanied by an alteration of smell. The air now 
 smells just like electricity discharging itself from a 
 point, or like the oxygen which is set free, for 
 example, on the positive pole in the electrolysis of 
 acidified water. The higher the temperature the 
 more rapid is the change which I have described; 
 and if the phosphorus is heated almost to its melting- 
 point, the alteration of smell and of voltaic condition 
 occurs in the course of a few minutes, or even in a 
 much shorter time ; while at the ordinary tempera- 
 ture several hours are required. When once the 
 
48 LETTEES OF BEBZELIUS 
 
 negative polarization or the electrical smell has 
 become perceptibly strong, a moist or air-dried strip 
 of litmus paper plunged in the air is fairly rapidly 
 bleached and tincture of litmus or indigo solution is 
 decolorized, exactly as it is by chlorine. If such air 
 is shaken with potassium ferrocyanide solution the 
 liquid becomes intensely yellow, and when treated 
 with pure ferrous sulphate gives a blue precipitate. 
 Potassium iodide solution shaken with it is turned 
 yellow, and moist starch paste mixed with this salt 
 instantly becomes blue. 
 
 I may mention here that strips of paper soaked in 
 starch solution containing potassium iodide form the 
 most convenient and the most delicate test for ozone ; 
 they indicate its presence even when a very sensitive 
 galvanometer fails to do so, or when the smell cannot 
 be perceived. 
 
 Just one example to prove the truth of this state- 
 ment. A small piece of phosphorus still covered 
 with moisture will not turn blue a piece of test 
 paper held above it, but if the phosphorus is rubbed 
 with blotting paper, with gentle friction, the paper 
 becomes decidedly blue in the course of a few seconds. 
 It is a remarkable fact that very small quantities of 
 ether or alcohol vapour, olefiant gas, as well as some 
 other vapours and gases, such as sulphurous acid, 
 hydrogen sulphide, etc., entirely prevent the forma- 
 tion of ozone in atmospheric air ; and this is the 
 action generally of all substances which arrest the 
 luminescence or slow combustion of phosphorus in 
 the air. I must here mention that in pure oxygen 
 
AND SCHONBELNT 49 
 
 no ozone is produced at temperatures at which in 
 atmospheric air it is formed in comparatively large 
 quantities. I need scarcely say that in hydrogen, 
 carbonic acid, ethylene, hydrogen sulphide, etc., no 
 ozone is formed ; but I should perhaps add that the 
 same is the case in nitrous oxide. It is further a 
 strange fact that the luminescence of phosphorus 
 stands in the closest possible connection with the 
 production of ozone and with the presence of nitrogen ; 
 but the limits of my space prevent me from going 
 further into this question, and therefore I take the 
 liberty of referring you to a memoir 1 which will 
 shortly appear in print, in which I have described 
 the results of my experiments in detail. As already 
 stated, the ozone which is obtained by the electrolysis 
 of water has every one of the properties of that which 
 I have prepared from phosphorus and atmospheric air, 
 so that not the slightest doubt remains as to the 
 identity of the two bodies. But that the strongly 
 smelling substance, produced by the discharge of 
 ordinary electricity, should be identical with chemical 
 and voltaic ozone is a fact which is as singular as it 
 is now (in my opinion, at least) unquestionable. The 
 experimental proofs of the correctness of my assertion 
 are as follows: 1. The bleaching power of the sub- 
 stance produced by the electric discharge. The 
 accompanying strip of paper marked No. 1 2 has been 
 
 1 The book mentioned above, on the chemical preparation of 
 ozone. 
 
 2 This and the other strips are still attached to the letter, and 
 show clearly the similarity of the bleaching action. 
 
50 LETTEES OF BEKZELIUS 
 
 bleached by electricity in the following manner. 
 The strip, in a moist condition, was placed on a 
 platinum plate which was in metallic contact with 
 the earth. A brass wire was fixed to the conductor 
 of the electrical machine so that its free end reached 
 to within a third of an inch of the strip. When the 
 electrical machine was set in motion, part of the strip 
 was thus in the electrical brush, that is, in the place 
 where the electric smell was most distinctly perceptible. 
 After the machine had been worked continuously for 
 four hours the strip appeared bleached as you see it. 
 (You will perhaps be interested to learn that the 
 strip which I am sending you is the very one with 
 which I for the first time proved the bleaching power 
 of the electrical odour, and that this first experiment 
 was performed on the 7th of April 1844.) 2. The 
 power possessed by the odoriferous electrical material 
 of converting potassium f errocyanide into f erricyanide. 
 A drop of ferrocyanide solution brought under the 
 above conditions assumes even after a few minutes 
 a deep yellow colour, and then on treatment with 
 pure ferrous chloride or sulphate gives a decided 
 blue precipitate. After a thousand turns of my 
 machine, a drop of such a solution gives a dark 
 blue precipitate. 3. The power possessed by the 
 electrical odour of almost instantly turning starch 
 paste containing potassium iodide blue. This power 
 has indeed long been known, but it has been errone- 
 ously interpreted ; for the separation of iodine does 
 not depend on the electrical decomposition of the 
 haloid salt, nor essentially on the formation of nitric 
 
AND SCHONBEIN 51 
 
 acid, as Faraday supposes. It is to the production 
 of ozone by the electricity that this action must be 
 ascribed. 4. The property of the electrical odour of 
 being destroyed by sulphurous acid, hydrogen sulphide 
 and hydrogen selenide. If in the neighbourhood of a 
 point from which electricity is being discharged the 
 merest trace of sulphurous acid is developed, as for 
 example by burning the sulphur of an ordinary match, 
 the peculiar smell which accompanies the discharge 
 of electricity into the air is perceived no longer. 
 Furthermore the electrical brush is no longer able 
 under these conditions to communicate negative 
 polarity to a gold or platinum strip held in it, or to 
 turn potassium iodide starch paste blue. Moreover 
 if such a strip is held only for a moment in a flask 
 containing some sulphurous acid, it will not be turned 
 blue when exposed to the action of the electric brush. 
 The action of hydrogen sulphide and selenide is 
 similar to that of sulphurous acid; the presence of 
 the smallest quantities of these substances in the 
 room containing the electrical machine is sufficient 
 to prevent the production of the electrical odour at 
 the point of the conductor and all the reactions de- 
 pending upon it. Now these substances destroy 
 chemically or voltaically prepared ozone in exactly 
 the same manner as the electrical odour. Hardly 
 any doubt can remain as to the identity of the ozone 
 prepared in the three ways described, and it may be 
 taken as incontestable that during the discharge of 
 electricity into the air a haloid substance similar to 
 chlorine is formed. Now since lightning is nothing 
 
52 LETTEES OF BEEZELIUS 
 
 but the restoration of electrical equilibrium on a 
 large scale, it seems to me to be certain that the 
 smell or pungent vapour observed after a flash of 
 lightning is nothing but my ozone. At any rate it 
 must form an important constituent of the odor- 
 iferous body which is so produced. My investigations 
 have shown that ozone is not produced either in pure 
 oxygen or carbonic acid under conditions of tempera- 
 ture in which it is produced quite easily in atmos- 
 pheric air ; and I have also found that in air which 
 is' completely dried with calcium chloride, my test 
 paper is coloured perceptibly blue, after this an- 
 hydrous air has been allowed to stand for some time 
 with phosphorus. Now this experiment seems to 
 show that water also contributes nothing to the 
 formation of ozone. 1 But if so, there is no known 
 constituent of the atmosphere left from which the 
 ozone could possibly originate, except nitrogen. 
 Though it is a very remarkable fact that ozone 
 should be produced by the electrolysis of water, and 
 also by the discharge of electricity in the air, yet it 
 is still more extraordinary that so eminently electro- 
 negative a body as this can be formed in the presence 
 of phosphorus and even by its means. Indeed if a 
 small piece of phosphorus is placed in a flask contain- 
 ing ozonized oxygen collected at the positive pole of 
 a battery, the ozone smell, the bleaching power, the 
 
 1 This remark is particularly interesting, because it is dia- 
 metrically opposed to his later view, which prevented him for 
 such a long time from accepting Marignac's explanation of the 
 nature of ozone, and de la Hive's proof that ozone can be 
 formed in the absence of water. 
 
AND SCHONBEm 53 
 
 negative polarity, and, in fact, all the properties of 
 ozone already specified disappear. If you take a 
 piece of phosphorus which would not shine in the 
 dark or colour a piece of my test paper placed near 
 it, and hold it near a point from which electricity is 
 being discharged, no ozone is developed at the point, 
 starch paste containing potassium iodide is not turned 
 blue, and generally none of the phenomena which I 
 have described as accompanying the electrical brush 
 are observed. Are we then to suppose that voltaic 
 and electric ozone are different from that which is 
 prepared from atmospheric air by means of phos- 
 phorus, and that chemical ozone cannot combine with 
 phosphorus ? 
 
 As a fact there is no such difference, as the follow- 
 ing experiment shows. If a few drops of ether are 
 allowed to fall into a flask filled with chemical ozone, 
 and then a small piece of phosphorus added, the ozone 
 smell rapidly disappears, and the test paper is no 
 longer turned blue by the air in the flask. The ozone 
 already present in a flask containing air and phos- 
 phorus is always destroyed, if by any of the means 
 which I have described, or in any other way, the 
 luminescence of the phosphorus is checked, that is, 
 its slow combustion prevented. To this, therefore, 
 is attributable the fact that the voltaic condition of 
 the air above the phosphorus can be repeatedly 
 altered, and depends essentially on the temperature ; 
 so that this air is sometimes positive, sometimes 
 negative, and sometimes neither. I may mention in 
 passing, that according to my experiments the 
 
54 LETTEKS OF BEEZELIUS 
 
 positive polarity of this air is chiefly due to phos- 
 phorus vapour, and also partly to traces of hydrogen 
 phosphide ; and it is easy to see from what I have 
 said, that these substances would exert a destructive 
 action on the ozone. This action of phosphorus 
 vapour may easily be shown by putting a test paper 
 ,first into it and then into an atmosphere of ozone. 
 As long as any traces of phosphorus vapour adhere 
 to the paper it will not be turned blue. Conversely, 
 if a test paper is turned blue by ozone and then 
 plunged into an atmosphere containing phosphorus 
 vapour, the blue colour disappears. 
 
 Finally I must mention, that if ozone is breathed 
 in small quantities it produces on the organism effects 
 similar to those produced by chlorine: coughing, 
 oppression of the chest, in short, all the symptoms of 
 a cold. A mouse placed in a flask filled with air con- 
 taining only very small quantities of ozone died after 
 five minutes in violent convulsions. From the results 
 described above, as well as from certain other facts 
 which I have discovered, some of which still remain 
 to be mentioned, it seems to me that we may con- 
 clude with a fair degree of certainty that nitrogen is 
 the source of ozone, or, to be more explicit, that 
 nitrogen consists of ozone and hydrogen. However 
 different the circumstances under which ozone is 
 formed may appear at first sight, there is yet one 
 condition which the electric, voltaic, and chemical 
 methods of production all fulfil alike, and that is 
 the presence of nitrogen. The formation of ozone by 
 ordinary electricity, by the voltaic current, and by 
 
AND SCHONBEIN 55 
 
 means of phosphorus may be explained as follows : 
 
 1. Electrical method of separation. Just as ordinary 
 electricity decomposes a series of gaseous hydrogen 
 compounds, especially in the presence of oxygen, so, 
 when it is discharged from a point into the air, it 
 determines the combination of the oxygen with the 
 hydrogen contained in the nitrogen and sets free the 
 ozone. If instead of nitrogen (i.e., hydrogen ozonide) 
 the atmosphere contained hydrogen chloride, the dis- 
 charge of electricity into the air would also produce a 
 smell, the feebler smell of chlorine; and, moreover, 
 the chemical actions which under these circumstances 
 the electrical brush would produce, would be quite 
 analogous to those which are actually observed. 
 
 2. Voltaic mode of production. The nitrogen, that is 
 the hydrogen ozonide, dissolved in water is, like 
 hydrogen chloride, an electrolyte. It is decomposed 
 by the current, its hydrogen being set free at the 
 negative pole, and its ozone at the positive. Boiled 
 out water, i.e., water free from nitrogen, does not give 
 the smallest trace of ozone on electrolysis, but if 
 shaken with air or nitrogen, then on passing the 
 current, ozone is again set free at the positive pole. 
 Hitherto I have not been able to find anything at 
 the negative pole but hydrogen. I may mention 
 here that the presence in the water of the smallest 
 quantities of sulphurous acid, hydrogen sulphide, and 
 other substances, which for example would prevent 
 the electrolytic liberation of chlorine, also stop the 
 formation of ozone. Sometimes even distilled water 
 contains substances which prevent its formation, even 
 
56 LETTEES OF BEEZELIUS 
 
 when our reagents are unable to detect the presence 
 of any foreign body in it. 3. Chemical method of 
 formation. Phosphorus in a state of slow combustion 
 exerts a catalytic action on the oxygen and nitrogen 
 in contact with it, causing the former to combine 
 with the hydrogen of the latter and set the ozone 
 free. Part of this ozone appears as a gas and mixes 
 with the air, while another part combines with the 
 phosphorus to form phosphorus ozonide, which is de- 
 composed by the water present into phosphoric acid 
 and hydrogen ozonide, i.e., nitrogen. This is the 
 reason why in moist atmospheric air the oxidation 
 of phosphorus proceeds so comparatively fast, and it 
 also explains the fact, that in the slow combustion of 
 phosphorus in air, not only phosphorous acid is pro- 
 duced, but also phosphoric ; the latter is undoubtedly 
 formed by means of ozone, while the immediate 
 result of the slow oxidation of the phosphorus is the 
 production of the former. 
 
 Similarly in the light of the facts which I have 
 discovered we can understand the long known and 
 remarkable property of nitrogen, of supporting the 
 luminescence of phosphorus. According to my ex- 
 periments, air standing over phosphorus and calcium 
 chloride does acquire a power of turning my test 
 paper blue, but very little ozone is formed under these 
 conditions, and hence very little phosphoric acid, 
 because the air cannot at first contain any water 
 vapour, and the water produced by the action of the 
 oxygen on the hydrogen ozonide is mostly absorbed 
 by the calcium chloride. Probably the formation of 
 
AND SCHONBEIN 57 
 
 phosphoric acid would proceed more rapidly in a dry 
 atmosphere in which no calcium chloride was placed 
 than in air containing a dehydrating agent. I have 
 not yet had time to try this experiment. 
 
 If I am right in what I have said, and there can 
 hardly be any doubt about it, the whole chemistry 
 of the nitrogen compounds will have to be regarded 
 from a totally new point of view, and in particular 
 nitric acid will have to be considered as ozonic acid, 
 a theory which is also supported by the great simi- 
 larity between the nitrates and the chlorates, etc. 
 We should probably have to consider nitrogen itself 
 as the first stage of the hydrogenation of ozone, the 
 amides being the second, ammonia the third, and 
 ammonium the fourth. I need not point out what an 
 importance nitrogen would have for meteorology if it 
 were hydrogen ozonide. Similarly certain diseases 
 might be due to ozone, and so forth. 
 
 I must now bring my letter to an end, and reserve 
 for another time the account of my investigations. It 
 would give me great pleasure if you would communi- 
 cate the contents of my letter to the Stockholm 
 Academy. You would be doing me the greatest 
 service if you would take an opportunity soon of 
 giving me your opinion and your criticism on my 
 experiments. 
 
 With the utmost respect, I have the honour to be, 
 My dear Baron, 
 
 Yours most sincerely, 
 
 C. F. SCHONBEIN. 
 
58 LETTEES OF BEEZELIUS 
 
 P.S. 1. Of the enclosed strips of litmus paper : 
 
 No. 1 is bleached by electrical ozone. 
 No. 2 by voltaic ozone. 
 No. 3 by chemical ozone. 
 
 P.S. 2. I must add that I have obtained potassium 
 nitrate by treating chemically-prepared ozone with 
 potash solution. I am hoping to discover, as well as 
 potassium ozonate, i.e., nitrate, potassium ozonide. It 
 is, no doubt, chemically possible that ozone, air, and 
 potash may give potassium nitrate. But at any rate 
 the fact that potassium nitrate is found under these 
 conditions is a very remarkable phenomenon, and 
 seems to go far to confirm the view expressed in my 
 letter that nitrogen is hydrogen ozonide. 
 
 An extensive extract from this detailed letter was 
 printed in the fifth number of the first year's publication of 
 the Ofversigt af Kongl. Vetenskaps Akademiens forhand- 
 lingar of 15th May 1844 [vol i., p. 71-75], and 
 next day Berzelius wrote personally to Schb'nbein. He 
 thought that the whole ozone question was still waiting 
 for a satisfactory solution, as is shown by the remarks 
 which he appended to Schonbein's letter, by his own 
 letter, and still more clearly from the Jdhresbericht. 
 He considered ozone, as he says there, to be a "proble- 
 matic body." 
 
 We need not be surprised at Schonbein's bold assump- 
 tion of the decomposition of nitrogen. Berzelius was 
 just the man whom he might expect to encourage him 
 in this view, for in his inmost heart he had always 
 believed l in the compound nature of nitrogen, although 
 
 1 Cf. Kose, Gedachtnisrede auf Berzelius, Berlin (1852), p. 27. 
 
AND SCHONBEIN 59 
 
 he was no longer prepared to stand by the assertion he 
 made in 1818 "that the compound nature of nitrogen is 
 not to be regarded merely as a hypothesis, but, if we grant 
 the law of constant proportions, as an almost established 
 fact." i 
 
 XI 
 
 Berzelius to Schbnbein 
 
 STOCKHOLM, IQth May 1844. 
 
 MY DEAR SIR, 
 
 I thank you sincerely for your extremely 
 interesting letter of 14th April, and for the scientific 
 novelties which it contains. In accordance with 
 your wish I laid it before the Koyal Academy 
 at their last meeting, and they ordered that an 
 extract from it be printed among their Transactions of 
 that meeting. 
 
 Now that you are able to produce ozone chemically 
 you could surely saturate a sufficient amount of air 
 with it to enable you to obtain its compounds in 
 weighable quantities. If, for example, you were to 
 
 1 Unersokning of Quafvets, Vatets och Ammoniakens natur. 
 Hisinger Afhandl. i Fysik, vol. v. (1818) p. 198 ; Gilbert, 
 AnnaL, vol. xlvi. (1814) p. 148. Previously, p. 133, he says : 
 " But my object is to prove that neither Gay-Lussac's analysis 
 of nitric acid, nor my own statements about the hyperbasic 
 salts considered above (the reference is to basic lead nitrate) are 
 right, and to show how by correcting these two analyses we can 
 remove satisfactorily all the objections which have hitherto 
 appeared to render the theory of the compound nature of 
 nitrogen untenable." 
 
60 LETTEES OF BEEZELIUS 
 
 put into your large glass flask, as well as phosphorus, 
 a flat vessel containing an amalgam of silver, lead, 
 zinc or tin, it seems to me that the metal dissolved in 
 the mercury would necessarily combine with ozone 
 to form a metallic ozonide, and the compound could 
 thus be prepared without the disturbing influence of 
 water, particularly if the metal chosen were one 
 which was not attacked by the vapours of phos- 
 phorous acid. After several weeks or a few months 
 an arrangement of this kind might give a sufficient 
 quantity of the substance for investigation. 
 
 Your theoretical ideas are extremely simple and 
 for that reason one would be glad to believe in them. 
 On the other hand they offer great difficulties. What 
 are the oxidation products of nitrogen if J? = OzH ? 
 Are they OzH + 1, 2, 3 and 5 atoms of oxygen ? In 
 that case OzH shows an inexplicable difference in 
 character from the ordinary substances which form 
 salts, for it ought to be a strong hydracid. Again 
 phosphorus, arsenic, and antimony form compounds 
 analogous in some degree to ammonia; but all of 
 them contain three equivalents of hydrogen, while 
 ammonia would have to be written OzH 4 . 
 
 On the other hand if nitric oxide, nitric acid, etc., 
 are to be Oz, 6z the theory does not accord with the 
 composition of these bodies, and particularly not with 
 their densities, the experimental values of which 
 agree so exactly with those calculated from their 
 composition. If a certain quantity of hydrogen gas 
 were driven out of the compound, in the combination 
 of nitrogen with oxygen, the gaseous product so formed 
 
AND SCHONBEm 61 
 
 should have a decidedly higher density. Indeed I do 
 not think the problem is yet in a position to be 
 solved. You must submit the older experiments of 
 Gottling l and Bockmann 2 to revision ; it is possible 
 that in their papers on the luminescence of phos- 
 phorus in nitrogen (particularly in that of the latter, 
 who declares that nitrogen disappears) you may find 
 facts which will suggest to you new methods of 
 research. The investigation is so important that you 
 must follow it up with the true Bunsen perseverance, 3 
 and not abandon it until, if possible, we are perfectly 
 clear about it. 
 
 I wish you patience and good luck in your research ; 
 and with assurances of the greatest respect, 
 I remain, 
 
 Yours most sincerely, 
 
 JAC. BERZELIUS. 
 
 1 Johann Friedrich August Gottling, born at Derenburg near 
 Halberstadt in 1755, died at Jena 1809. He was first an 
 apothecary, and then professor of chemistry, pharmacy, and 
 technology at Jena : " Etwas u'ber den Stickstoff und das 
 Leuchten das Phosphors in Stickluft," Cfren. Neues Journ., vol. 
 i. (1795) p. 1. 
 
 2 Carl Wilhelm Bockmann, born at Karlsruhe in 1773, died 
 in 1821, teacher of physics at the gymnasium there : " Ver- 
 suche u'ber das Verhalten des Phosphors in verschiedenen 
 Gasen," Erlangen, 1800. 
 
 3 He no doubt alludes in particular to Bunsen's investigations 
 on cacodyl which were begun in 1837, and whose conclusion 
 Berzelius had announced in the volume of the Jahresbericht 
 which was laid before the Academy on 31st March. 
 
62 LETTEES OF BERZELIUS 
 
 XII 
 Schonbein to Berzelius 
 
 MY DEAR BARON, 
 
 Since you considered my papers on ozone 
 worthy of your attention, I flatter myself that you 
 will be interested to hear of the results of my investi- 
 gations on a kindred subject. Owing to want of 
 space I will confine myself to general outlines, 
 especially as a detailed account of the substance in 
 question will shortly be published. 1 The combustion 
 of phosphorus in atmospheric air and the formation 
 of a highly electro-negative body possessed of marked 
 oxidizing properties, my ozone, directed my attention 
 to the combustion in air of bodies generally, especially 
 to cases analogous to the gradual oxidation of phos- 
 phorus, such as the partial combustion of ether 
 vapour at comparatively low temperatures. By 
 analogy, and in accordance with my theoretical 
 views as to the nature of nitrogen, I anticipated the 
 formation of a body with electro-negative and oxidiz- 
 ing properties. You will see that my results show 
 that the gradual oxidation of ether vapour (as well as 
 the rapid burning of bodies in general) is accompanied 
 by phenomena which so far have escaped the notice 
 of chemists, but which certainly appear to me to be 
 
 1 " Uber die langsame und rasclie Verbrennung der Korper 
 in atmospharischer Luff Bale, 1845. Dated 5th June 1845. 
 
AND SCHONBEIN 63 
 
 well worth careful attention. When a mixture of 
 ether vapour with atmospheric air is partially burnt 
 by means of a moderately heated platinum wire, 
 a substance is formed which has the following 
 properties : * 
 
 1. It decolorizes indigo solution. 
 
 2. It decomposes potassium iodide and hydrogen 
 
 iodide, setting iodine free, thus turning paper 
 moistened with starch and potassium iodide 
 blue. 
 
 3. It decomposes potassium bromide, though not 
 
 very readily. 
 
 4. It converts potassium ferrocyanide into the red 
 
 prussiate of potash. 
 
 5. It immediately imparts a deep colour to white 
 
 ferrous cyanide. 
 
 6. It changes ferrous into ferric salts. 
 
 7. In the presence of water it oxidizes iodine to 
 
 iodic acid. 
 
 8. In presence of water it changes sulphurous into 
 
 sulphuric acid. 
 
 9. It readily decolorizes sulphide of lead and other 
 
 metallic sulphides, apparently converting 
 them into sulphates. 
 
 10. It renders an aqueous solution of sulphuretted 
 
 hydrogen unable to precipitate lead salts. 
 
 11. A concentrated solution of the substance, 
 
 possessing all the aforementioned properties, 
 
64 LETTEKS OF BEEZELIUS 
 
 loses them so soon as it is brought in contact 
 with oxidizable substances, e.g., sulphurous 
 acid or metals. 
 
 12. Even mercury reacts in this way, with the 
 formation of a mercury salt soluble in water. 
 
 If hydrogen is burned in atmospheric air and the 
 following liquids are held over the point of the flame 
 in narrow tubes, the following reactions take place : 
 
 1. Indigo solution becomes decolorized. 
 
 2. Iodine is liberated from potassium iodide and 
 
 hydrogen iodide solutions or paper moistened 
 with starch paste and potassium iodide be- 
 comes blue. 
 
 3. A potassium ferrocyanide solution assumes an 
 
 intense yellow coloration, is, in fact, converted 
 into potassium ferricyanide. 
 
 . 4. White ferrous cyanide suspended in water turns 
 dark blue. 
 
 5. A ferrous salt in solution is converted into a 
 
 ferric salt. 
 
 6. Aqueous sulphurous acid is transformed into 
 
 sulphuric acid. 
 
 7. Lead sulphide suspended in water is bleached. 
 
 A slip of paper saturated with water and 
 coloured brown with lead sulphide turns 
 white on being held over the point of the 
 flame. 
 
AND SCHONBEIK 65 
 
 The very same reactions, only in a more pronounced 
 degree, can be brought about with the help of the 
 flame of an ordinary candle, by merely leading into 
 it a current of atmospheric air as in testing with the 
 blow-pipe. Thus the remarkable fact appears that 
 the results are due to the oxidizing, and under no 
 circumstances to the inner or reducing flame. The 
 simplest method of demonstrating one of these re- 
 actions is to draw a strip of paper, wetted with water 
 and saturated with starch paste, through the oxidiz- 
 ing flame ; wherever the latter touches it, it becomes 
 as blue as if it had been exposed to the action of 
 electricity. In the reducing flame on the other hand 
 this coloration vanishes immediately. 
 
 I also blew a current of air through a phosphorus 
 flame, and I got indications of the occurrence of the 
 above reactions; starch and potassium iodide in 
 particular become blue in the neighbourhood of the 
 tip of the flame. The flames of camphor and other 
 similar bodies of course resemble that of an ordinary 
 candle. The fact that in a sulphur flame such 
 oxidizing agents are not formed is explained by the 
 presence of sulphurous acid ; and in this connection 
 it is remarkable that water, upon which a sulphur 
 flame is allowed to play by means of a blow-pipe, in- 
 variably contains an appreciable quantity of sulphuric 
 acid. 
 
 The results of my investigations therefore go to 
 show that any body, when burned in atmospheric 
 air, produces an electro-negative oxidizing substance. 
 But whether all forms of combustion give the same 
 
 8 H A 
 OF THE 
 
 ( UNIVERSITY I 
 
66 LETTEES OF BEEZELIUS 
 
 substances, that is to say, whether the substances 
 formed by the gradual oxidation of phosphorus 
 and of ether vapour are identical with those 
 produced by the rapid combustion of the other 
 bodies, must be decided by further investigations. 
 At any rate this important fact remains, that the 
 substances in question show a remarkable resemblance 
 to one another in their properties. That they have 
 nothing in common with nitric or nitrous acid, is 
 obvious from the way in which they are produced ; 
 but there are also other reasons which go against this 
 assumption. The facts I have mentioned hardly over- 
 throw my hypothesis as to the nature of nitrogen; 
 they go to show that high temperatures would cause 
 the oxygen of the air to combine with the hydrogen 
 of the nitrogen and set ozone free ; this may be com- 
 pared to the way in which I imagine the catalytic 
 influence of phosphorus or ordinary electricity would 
 act on a mixture of oxygen and nitrogen. However, 
 I do not wish to attach any great importance to this 
 view, but only add that such results possess a peculiar 
 interest in regard to the opposite chemical effect 
 caused by the two parts of the blow-pipe flame. I 
 have no doubt that the oxidizing power of the outer 
 flame is due to some peculiar substance and not 
 directly to ordinary heated oxygen. 
 
 I should of course be glad if you would communi- 
 cate the contents of this letter to your Academy, if 
 you think it of sufficient importance. 
 
 I hope that this note will find you in good health, 
 
AND SCHONBEIN 67 
 
 and I trust that you will honour me soon with a few 
 lines in reply. 
 
 With the profoundest respect, I have the honour to 
 
 remain, 
 
 Yours most obediently, 
 
 C. F. SCHONBEIN. 
 
 P.S. I trust you have received my paper on ozone. 
 BALE, 15th January 1845. 
 
 This letter also was read at the Academy in Stockholm, 
 and a summary of it appeared in the Ofversigt of Kongl. 
 Vetenskaps Akadamiens forhandlingar [vol. 2. (1845) 
 p. 1.8]. Two days after this meeting, which took place 
 on 12th February, Berzelius sent the following reply 
 to Schonbein : 
 
 XIII 
 Berzelius to Schonbein 
 
 STOCKHOLM, \Uh February 1845. 
 
 DEAR SIR, 
 
 I thank you very much for your interesting 
 communication in your last letter of 15th January, 
 which I read before the Academy and which they 
 are publishing in their Transactions. I think you 
 have proved that ozone is always formed during 
 combustions in atmospheric air ; hence there only 
 
68 LETTEES OF BEEZELIUS 
 
 remains the further step of producing an unmistak- 
 able compound of this body with some other in such 
 quantity as to make it possible to study its properties 
 accurately. If you lead a current of air first through 
 ether and then through platinum sponge this can 
 readily be effected by means of an aspirator, and 
 continued for weeks together you might collect a 
 considerable quantity of the products of combustion ; 
 they would be little else than water, carbonic acid 
 and ozone. If, as you state, the liquid dissolves 
 mercury, forming a soluble salt, you might condense 
 it over mercury and thus obtain a quantity of the 
 mercury salt, whose properties could then be 
 investigated. 
 
 I did not get your detailed paper, but I am 
 acquainted with it from the French translation in 
 de la Eive's Archive de I' filectriciU. 1 I candidly 
 confess that I am not quite satisfied with the experi- 
 mental part of it ; in the first place the preparation 
 of the potassium salt is tremendously laborious, and 
 in the next place the reactions which you have 
 performed with the new salt are not carried out 
 on correct principles. For you assert that all 
 acids evolve from it an odour of ozone, the acid 
 uniting with the potassium. This is much as 
 though sulphuric acid were to produce a smell of 
 chlorine with common salt. You should have tried 
 it with chlorine or bromine water in order to set 
 ozone free. If, however, which I do not doubt, your 
 assertion be correct, the odour must be due to hydro- 
 5 V Electricity vol. iv. (1844) p. 333. 
 
AND SCHONBEIN 69 
 
 ozonic acid ; now if such an acid does exist and can 
 be prepared, it seems fairly evident that nitrogen 
 cannot be hydrogen ozonide. It would therefore be 
 better to put on one side all theoretical conjectures 
 as to the constitution of ozone and nitrogen and to 
 study the properties of ozone itself. When once you 
 have caught it, it will be easier to theorize about it. 
 I hope you will excuse my candid remarks. 
 
 With the kindest regards, 
 
 I have the honour to remain, 
 
 Yours obediently, 
 
 JAC. BERZELIUS. 
 
 From the postmark this letter reached Bale on the 26th 
 of February ; Schonbein therefore answered it by return 
 of post. 
 
 XIV 
 Schonbein to Berzelius 
 
 MY DEAR BARON, 
 
 I must ask you to forgive me for troubling you 
 so soon with another letter ; but some remarks which 
 you were so good to make on my larger research con- 
 cerning ozone, in your honoured letter of the 14th of 
 last month, have induced me to send you a few words 
 in reply. In the first place I take the liberty of re- 
 marking that the paper in question, in the last 
 number of de la Eive's Archives, absolutely teems 
 
70 LETTEES OF BEEZELIUS 
 
 with errors of translation, so that in some cases its 
 meaning is the exact opposite of that of the German 
 original. 
 
 In my paper the salt obtained by the complete 
 decomposition of potassium iodide by means of ozone 
 was not said to be pure potassium ozonide (although 
 I was certainly inclined at first to think it was that) ; 
 on the contrary it was expressly stated that it con- 
 tained potassium iodate. 1 Also I have nowhere said, 
 as far as I know, that all acids gave with this salt 
 a smell of ozone. I did indeed remark that sulphuric 
 acid set free from it a constituent which had a smell 
 apparently intermediate between that of bromine and 
 that of iodine, and which turns potassium iodide 
 starch paste blue, etc., but I did not venture de- 
 finitely to ascribe this smell to ozone, though I 
 expressed an inclination to believe that it was due to 
 it. Assuming that the salt in question contains 
 some potassium iodate as well as potassium ozonide, 
 I expressed myself to the following effect as to the 
 supposed development of ozone, on pages 116 and 117 
 of the German paper 2 : "The production of ozone 
 from this mixture of salts by means of sulphuric acid, 
 the brown colour which the acid causes, and the 
 evolution of iodine vapours on warming, are satis- 
 factorily explained if we suppose that the salt in 
 question is a mixture of potassium iodate and 
 
 1 Cf. also Berzelius' remarks in the Jahresbericht, vol. xxv. 
 (1846) p. 132. 
 
 3 Schonbein is here referring to the earlier paper : Uler die 
 Erzeugung des Ozons. 
 
AND SCHONBEIN 71 
 
 potassium ozonide. The sulphuric acid separates the 
 iodic acid from the potash, and part of the oxygen of 
 the latter acid combines with the potassium of the 
 ozonide, setting free iodine and ozone." This single 
 passage is, I think, sufficient to place the point in 
 question in the right light. It was not because I 
 had not thought of the method that I did not treat 
 my salt with chlorine. But I only had, so to speak, 
 homoeopathic quantities of the salt, and so I could 
 only perform a few incomplete experiments with it ; 
 and as I wished to see whether I could obtain from 
 it a body similar in its reactions to chlorine or ozone, 
 I intentionally abstained from employing the former. 
 Originally I mixed my salt with pure manganese 
 dioxide, and then on treating it with sulphuric acid 
 I obtained the reactions I have described; but I 
 found out later that the manganese dioxide was 
 quite unnecessary, and that the reaction was due to 
 the presence of potassium iodate. The fact that a 
 solution of the salt, when treated with any acid 
 colours starch paste containing potassium iodide blue, 
 likewise makes the presence of potassium iodate con- 
 ceivable. However, I do not attach any importance 
 to these preliminary experiments, since they were 
 performed, as I have said, with such small 
 quantities. 
 
 You are quite right in saying that the plan which 
 I have adopted of using potassium iodide to absorb 
 the ozone, liberated by means of phosphorus, is very 
 laborious, but I am bound to say that up to the 
 present moment I know of no better. Mercury, for 
 
72 LETTEES OF BEKZELIUS 
 
 instance, takes such an endless time to absorb ozone, 
 set free by phosphorus, that I can hardly believe it 
 will ever be employed as a means of separating it. 
 At all events the fact is, that there is no material 
 which is able to take up ozone more rapidly than 
 potassium iodide. I willingly admit that you are quite 
 right in blaming me for indulging in my paper in too 
 much speculation about ozone ; I will not attempt to 
 justify this offence even by saying that it is never so 
 often committed as in chemistry, as has been amply 
 shown in recent times. I am sure that you will 
 readily grant that the circumstances under which 
 ozone is produced inevitably lead one to think of the 
 possibility of nitrogen being a compound. However 
 baseless my hypothesis as to the nature of this body 
 may be, it has guided me in all the experiments I 
 have hitherto made, and has led me to a series of 
 discoveries. Whatever ozone may prove to be, this 
 much seems to me to be certain, from its voltaic and 
 chemical properties, that it is not a hydrogen com- 
 pound or at least not a hydracid. 
 
 As soon as I am quite well again I shall continue 
 my experiments on ozone with renewed zeal ; but I 
 have for some time been condemned to inaction in 
 consequence of a cold which I have no doubt that I 
 caught through breathing too much of the gases 
 produced by the slow combustion of ether 
 vapour. 
 
 I have for a long time been very anxious to visit 
 your beautiful country, and as soon as I am able to 
 carry out my project I shall lose no time in doing so ; 
 
AND SCHONBEIN 73 
 
 in which case I shall take the liberty of paying my 
 respects to you in person. 
 
 With the greatest esteem, 
 I have the honour to be, my dear Baron, 
 
 Yours most sincerely, 
 
 C. F. SCHONBEIN. 
 BALE, 1st March 1845. 
 
 The following letter was written to Berzelius three 
 weeks later, and communicated to the Royal Academy of 
 Stockholm at their meeting of April the 9th, together 
 with a letter written by Plantamour of Geneva on 
 February the 4th, describing Marignac's first work on 
 ozone. In this letter there is as yet no allusion to the 
 possibility of ozone being a form of oxygen. This was 
 first suggested in another letter of Plantamour's of the 
 20th of April of the same year, which was laid before the 
 Academy on the 21st of May, and printed in the Ofver- 
 sigt, Arg. 2 (1845) p. 116. 
 
 XV 
 Schbnbein to Berzelius 
 
 MY DEAR BARON, 
 
 I believe I have at last succeeded in solving 
 the ozone riddle ; and I think you and your colleagues 
 of the Eoyal Academy, as you have attached some 
 importance to the subject, will find the following 
 communication worthy of your attention. 
 
74 LETTEES OF BEEZELIUS 
 
 After all my attempts to isolate ozone had failed, 
 and I had never got any results save oxidations, I 
 was induced to reconsider the conditions under which 
 ozone is produced. Five years ago, when I prepared 
 ozone voltaically, my first idea was that it was a body 
 in a higher state of oxidation ; and so starting again 
 from this view I investigated the part which water 
 plays in the production of the substance. I found 
 that by the action of atmospheric air on phosphorus 
 in contact with water at 30, ozone is produced in 
 larger quantities than in any other case, and moreover 
 that its production is continually diminished as the 
 air approaches nearer to dryness. Just the same 
 results were obtained if I performed the experiment 
 with a mixture of ozone and carbonic acid, but no 
 ozone was produced if oxygen alone, or nitrogen, or 
 carbon dioxide was allowed to act on the phosphorus. 
 It seemed therefore as if ozone was produced from 
 oxygen and water, and as if nitrogen played no 
 essential part in its formation. 
 
 As much as five years ago I published my observa- 
 tions that the discharge of electricity from a heated 
 point did not produce the so-called electrical smell, 
 and that the voltaic current was not able to set free 
 any ozone from heated water. 1 Similarly I found 
 that a heated platinum strip held in the discharge 
 from a cold point receives no negative charge, just as 
 happens when the point is hot and the strip cold. 
 Therefore, proceeding on the hypothesis that ozone 
 may be a higher oxidation product of hydrogen which 
 1 Poggend. Annal., vol. 1. (1840) p. 618. 
 
AND SCHONBEIN 75 
 
 is decomposed by heat, I made the following experi- 
 ments. Ozone was produced in a large flask by the 
 usual chemical method in as large quantities as 
 possible, and a suitable arrangement was made 
 whereby the atmosphere charged with ozone was 
 caused to pass through a narrow glass tube into the 
 air. As long as the tube was not heated, the issuing 
 air had a smell quite indistinguishable from that 
 noticed in the neighbourhood of a point from which 
 electricity is being discharged, and it also produced 
 all the chemical and voltaic reactions which are 
 characteristic of chemical, voltaic and electrical ozone. 
 Thus it gave a negative charge to platinum, it turned 
 starch paste containing potassium iodide blue, it 
 destroyed vegetable colours, etc. But if about an 
 inch of the tube is heated by means of a spirit lamp 
 the peculiar smell disappears, and at the same time 
 the air loses all its peculiar properties. If the tube 
 is allowed to cool again, all these properties reappear. 
 Voltaic ozone of course behaves in exactly the same 
 way under the same conditions. The complete 
 similarity of the action of heat on chemical, voltaic 
 and electrical ozone may serve as a further proof of 
 the identity of these substances. 
 
 A few days ago my friend Marignac l of Geneva 
 informed me of the results of the experiments which 
 he has carried out with a view to the isolation of 
 ozone and the determination of its properties. They 
 
 1 Jean Charles Galisard de Marignac, born at Geneva in 
 1817, died in 1894. Professor of chemistry at the University 
 of Geneva from 1842 to 1878. 
 
76 LETTEES OF BEKZELIUS 
 
 are so interesting that I venture to communicate 
 them to you. This distinguished chemist obtains 
 from water completely freed from air and acidified 
 with pure sulphuric acid, large quantities of ozone if 
 the liquid is kept cool. Finely divided silver, which 
 rapidly absorbs ozone, forms with it nothing but 
 silver oxide ; potassium iodide gives only potassium 
 iodate and some carbonate. He fails, as I did, to get 
 any ozone with pure oxygen or with carbonic acid 
 or nitrogen, but he obtains it from both the two 
 last-named gases as well as from hydrogen, if they 
 contain free oxygen. It is easy to see by comparing 
 Marignac's results with mine, that the two series 
 supplement and confirm one another, and I think we 
 may fairly conclude from them, that oxygen and 
 hydrogen are the constituents of ozone, and that the 
 latter is formed whenever oxygen comes in contact 
 with water under the requisite conditions. The pro- 
 duction of ozone in the electrolysis of water can easily 
 be understood ; to explain the action of phosphorus 
 and electricity, we must suppose that they exert a 
 catalytic influence on the oxygen and the water. The 
 following facts seem to make it certain that ozone is 
 not identical with The'nard's hydrogen peroxide. 1 
 The latter has no smell, dissolves in water in all pro- 
 portions, communicates to platinum, according to 
 Becquerel's and my own observations, a positive 
 charge, and is converted by the catalytic action of 
 
 1 Th^nard, " Memoire sur la combiuaison de 1'oxigene, et sur 
 les proprits extraordinaires que possede 1'eau exigence," 
 Memoires de PAcadJmie, Paris, vol. iii. (1820) p. 385. 
 
AND SCHONBEIN 77 
 
 silver into water and oxygen : whereas ozone is dis- 
 tinguished by a highly characteristic smell, scarcely 
 dissolves in water even in traces, charges platinum 
 negatively, and oxidizes silver. Since ozone is pro- 
 duced by the influence of electricity in atmospheric 
 air, and since restorations of electrical equilibrium 
 are] continually occurring, it follows that the air must 
 contain ozone. Now in the open air starch paste 
 containing potassium iodide turns blue, and potassium 
 iodide forms the iodate with the liberation of iodine 
 (though only to a small extent) ; and since in a closed 
 vessel none of these phenomena occur, and since they 
 are produced by the action of ozone on potassium 
 iodide, it would seem that we ought to ascribe them 
 to the atmospheric ozone. But if so, many slow oxi- 
 dations which take place in the air, such as bleaching 
 and various other similar phenomena, must also be due 
 to the atmospheric ozone, and not to the free oxygen 
 of the air. From the powerful physiological effects 
 of ozone, its presence in the air may have a medical 
 interest. The luminescence of phosphorus in atmos- 
 pheric air, which has so long been known and is so 
 little understood, can now be explained fairly satis- 
 factorily. The catalytic influence of the phosphorus 
 determines the combination of the oxygen and the 
 water to form ozone, which in its turn oxidizes the 
 phosphorus to phosphoric acid. The simultaneous 
 production of phosphorous acid is no doubt due to 
 the direct combination of the atmospheric oxygen 
 with the phosphorus. In absolutely dry air the 
 luminescence of phosphorus is excessively feeble, and 
 
78 LETTEES OF BEEZELIUS 
 
 no ozone is formed, from which it would seem to 
 follow that the production of light depends chiefly 
 on the oxidation caused by the ozone. At least it is 
 a fact that the amount of ozone formed is exactly 
 proportional to the intensity of the luminescence 1 
 of the phosphorus. The great similarity between 
 ozone and chlorine leads one to think of the old views 
 about the latter, and it is possible that sooner or later 
 this hypothesis, which you supported for so long, may 
 again become the subject of discussion. 
 
 Pray communicate the contents of this letter to 
 the Eoyal Academy if you find it sufficiently interest- 
 ing. 
 
 With the greatest respect, 
 I have the honour to remain, my dear Baron, 
 Yours very sincerely, 
 
 C. F. SCHONBEIN. 
 
 BiLE, mnd March 1845. 
 
 It seems from this letter, from the paper, "Uberdie 
 Natur des Ozons" [Poggend. Annal, vol. Ixv. (1845) 
 p. 69], which is dated Holy-Thursday, 1845, i.e., 20th 
 March, and from the simultaneous publication of the two 
 works in the Archives de VMedridte, vol. v., Marignac, 
 pp. 5-11 ; Schonbein, pp. 11-23, that Schonbein was not 
 
 1 We do not yet know why the catalytic influence of phos- 
 phorus is not exerted in oxygen of the ordinary density, but 
 only when the gas is rarefied to a certain extent either by itself 
 or by dilution with certain other gases. [This note is by 
 Schonbein.] 
 
AND SCHONBEIN 79 
 
 led to his new view as to the nature of ozone by Marignac, 
 but only confirmed in it by the simultaneous work of the 
 latter. 1 
 
 XVI 
 Schonbein to Berzelius 
 
 MY DEAR BARON, 
 
 I take the liberty of sending you, by favour 
 of Herr von Mitscherlich, two papers which I have 
 just published on ozone and kindred subjects. I 
 hope you will receive them with indulgence, as a 
 slight mark of my unbounded esteem. 
 
 I have for some time been busy with experiments 
 on the formation of nitric acid, and I have been 
 successful in discovering some facts which appear 
 to me to throw a certain amount of light on this 
 subject, which has hitherto been very imperfectly 
 understood. I have come to the conclusion that the 
 production of nitric acid is closely connected with 
 the action of ozone ; it seems that the latter, under 
 some conditions, can oxidize nitrogen to nitric acid. 
 This much is certain, that nitric acid is formed in 
 the production of ozone in atmospheric air by the 
 chemical method (by the means of phosphorus), just 
 as it is by passing electric sparks through a moist 
 mixture of oxygen and nitrogen. This is evident 
 
 1 Cf. Engler, " Historisch-Kritische Studie iiber das Ozon " 
 (reprint from the Leopoldina\ Halle (1879), p. 8. 
 
80 LETTEES OF BEEZELIUS 
 
 from the fact that the so-called phosphoric acid, 
 produced by the phosphorus in moist air, always 
 contains nitric acid. I shall soon publish in 
 Poggendorff's Annalen some more details on this 
 not uninteresting subject. You may possibly be 
 interested to have a little sample of the bleaching 
 action of ozone, and so I have taken the liberty of 
 enclosing two strips 1 of linen, one of which has been 
 hung for about a fortnight in air which has been 
 ozonized by means of phosphorus. The second is 
 a sample of the unbleached stuff. I must add that 
 the bleaching of the white strip was accomplished 
 solely by means of ozonized air. 
 
 I am still wholly unable to understand how they 
 can have found in the Giessen laboratory that by 
 the action of phosphorus on moist air no substance 
 is produced which bleaches, decomposes potassium 
 iodide, and in other ways shows itself a strong 
 oxidizing agent. I confess that the experiments 
 have been performed there in a way which could not 
 lead to any but negative results. 
 
 We had almost persuaded ourselves here that on 
 the occasion of your recent visit to Germany we 
 should have the pleasure of seeing you in our house, 
 and we had made preliminary arrangements to do 
 you honour; but unfortunately these hopes, which 
 were based on the statement of a man from Berlin, 
 have not been realized. 
 
 Indulging in the pleasant expectation of soon 
 
 1 Both strips are still enclosed in the letter. 
 
AND SCHONBEIN 81 
 
 being honoured by a letter from you, I beg to 
 remain, my dear Baron, 
 
 Yours most sincerely, 
 
 C. F. SCHONBEIN. 
 
 BALE, SQtJi September 1845. 
 
 XVII 
 
 Schbnbein to Berzelius 
 
 MY DEAR BARON, 
 
 In the course of my latest experiments on 
 ozone, I have obtained some results of a rather unusual 
 kind, which I think are not wholly without import- 
 ance to science. In particular I have succeeded in 
 producing a most remarkable change in a series of 
 organic bodies ; for example, I have converted sugar 
 into a resin, that is, into a substance soluble in ether, 
 alcohol, fatty oils, etc., but insoluble in water. One 
 of the most peculiar transformations that I have 
 effected is in vegetable fibre, which I have brought 
 into such a condition that it is readily soluble in 
 ether and alcohol, but unaffected by water, and if 
 properly prepared, possesses the transparency of glass. 
 On this change of vegetable fibre I have founded 
 a process which enables me to convert ordinary 
 unsized paper into a substance having the following 
 properties. 
 
82 LETTEES OF BEKZELIUS 
 
 1. However long it is exposed to the action of 
 water it retains its coherence, which, moreover, is 
 so much increased by my process that the paper has 
 a texture like that of parchment. 
 
 2. Also, acid and alkaline solutions, as, for example, 
 water containing hydrochloric acid or potash, have 
 no destructive action on the prepared paper ; and so 
 ordinary and printing ink can be removed from it 
 without injury to its durability. 
 
 3. Thin and extremely brittle paper acquires, by 
 my process, a firmness and toughness equal to that 
 of much thicker ordinary paper of the toughest 
 texture. 
 
 4. No size or starch is required to make it avail- 
 able for printing and writing. It takes ordinary and 
 also lithographic printing with great ease. 
 
 5. The detrimental action of bleaching powder is 
 done away with by my process. 
 
 These properties are of such a kind, I think, as to 
 ensure that my paper will be very much used ; and, 
 moreover, my process has the advantage that it 
 allows of a much larger number of sheets being 
 made from the same quantity of rags than in the 
 ordinary method of paper-making; for, as I have 
 already said, my paper is decidedly stronger and 
 tougher than much thicker paper of the usual kind. 
 I have not yet ascertained how much thinner the 
 waterproof paper may be than ordinary unprepared 
 
AND SCHONBEIN 83 
 
 paper of the same size so as to be equally tough ; but 
 it is certain that a single thickness of the prepared 
 paper is at least as strong as a double thickness of 
 ordinary paper. 
 
 In order that you may be in a position to convince 
 yourself by actual observation that my paper does 
 possess these properties, I have taken the liberty of 
 enclosing some paper strips. Those which bear the 
 same numbers are taken from the same sheet, one 
 being prepared and the other in its natural 
 condition. If you put the strips into water, you 
 will easily be able to distinguish the prepared 
 paper from the normal paper by the difference in 
 their behaviour. 
 
 It seems to me that my process, which, by the 
 way, is as cheap as it is simple, is particularly 
 adapted for preparing printing, packing, and wall- 
 paper. As enormous quantities of paper are used 
 for these purposes, I should imagine that a knowledge 
 of my process would be welcomed by paper-makers. 
 I therefore venture to ask you whether any influential 
 Swedish paper-makers would be inclined to put 
 themselves into communication with me with a view 
 to making use of my method, or whether your 
 Government would receive instructions concerning 
 the details of it, in the interest of the paper industry 
 of the country. You would oblige me exceedingly 
 if you would kindly give an answer to these 
 questions. 
 
 I shall shortly send you a full account of the 
 means by which I have obtained these results, and of 
 
84 LETTEKS OF BEEZELIUS 
 
 the conclusions of my recent work in general which 
 may perhaps serve as a communication to your 
 Academy. 
 
 The transparent parchment-like leaf is modified 
 vegetable fibre, which I can prepare in any required 
 quantity. 
 
 In the pleasant anticipation of soon receiving an 
 answer, 
 
 I have the honour to remain, 
 With the utmost respect, my dear Baron, 
 Yours most sincerely, 
 
 C. F. SCHONBEIN. 
 
 P,S. The unmarked bit of paper had been printed 
 on, and the printer's ink was removed by potash. 1 
 
 BALE, 5th March 1846. 
 
 These two letters of Schonbein's of the 20th' of Sep- ' 
 tember 1845 and the 5th of March 1846 also remained 
 unanswered, at least there is no reply among the papers 
 which have come into my hands. But on 'the 8th of 
 April following Berzelius gave the Academy an exhaustive 
 account 6f the letter of March the 5th, in which he also 
 alludes to the earlier communication. On this occasion 
 he once more referred expressly to Marignac's views as to 
 the nature of ozone. 
 
 I do not feel quite sure whether there was not another 
 letter of Schonbein's which is now lost, coming between, 
 those of March 5th and June 20th. His expression in 
 
 1 Seven different samples of paper are attached to this letter. 
 
AND SCHONBEIN 85 
 
 the letter of June 20th seems to me to indicate this : 
 "It will perhaps interest you to know that I have made 
 many experiments with my guncotton." This alone is 
 enough to show that the writer assumes on the part of 
 Berzelius an accurate acquaintance with the then state of 
 affairs; and this would be simply and easily explained 
 from the correspondence which they were usually so fond 
 of keeping up. Though according to Schonbein's own 
 account in the Allgemeine Zeitung of 25th October 1846, 
 the first experiments with guns on a large scale had been 
 performed in the week April 6-12, and the discovery 
 had attracted the attention of the general public to a 
 very unusual degree, Schonbein had given a public lecture 
 on his first invention for the first time as late as May 
 27th, before the Scientific Club of Bale. In this lecture 
 he referred directly to the experiments described in the 
 letter of March 5th, on which moreover he had not 
 lectured to the Club till March llth, after he had com- 
 municated them to Berzelius. So if Berzelius knew about 
 the experiments with guncotton he must have derived the 
 information either from Schonbein directly or from notices 
 in the papers, for the scientific journals had not yet 
 received accounts of them j and this last assumption 
 seems to me, as I have said, to be rendered untenable by 
 the expressions which Schonbein employs. 
 
86 LETTEES OF BEKZELIUS 
 
 XVIII 
 
 Schonbein to Berzelius 
 
 DEAR SIR, 
 
 I hope you will forgive me for taking the 
 liberty of introducing to you with these lines two 
 young men from Bale, Herr Merian 1 and Herr 
 Landerer, 2 and of commending them to your favour- 
 able notice. They are going to travel in your 
 beautiful country chiefly for artistic purposes. 
 
 You will perhaps be interested if I take this 
 occasion of informing you that I have just recently 
 performed numerous experiments with my guncotton 
 both with small firearms and with large guns, and 
 I have obtained the most satisfactory results. For 
 instance I sent a shell weighing 15 Ibs. (7J kgs.) 
 1670 French feet from a mortar with one ounce 
 of my guncotton ; and with half a drachm (1*7 grms.) 
 a gun sent a bullet weighing three-quarters of an 
 ounce several inches deep into wood at a distance 
 of 500 feet. The experiments which I have hitherto 
 made have shown that one pound of guncotton 
 produces at the very least as much effect as two 
 pounds of the best gunpowder. I have several times 
 used my guncotton for blasting purposes in a tunnel 3 
 
 1 Eduard Merian-Bischoff, born at Bale in 1824, died in 1859. 
 
 2 He became a painter ; he was murdered at Barbizon near 
 Paris on September 6th, 1893. 
 
 3 The tunnel of the Baden railway near Istein. 
 
AND SCHONBEIN 87 
 
 which is being made through muschelkalk in our 
 neighbourhood, and in the opinion of the work- 
 men it was as effective as three times the quantity of 
 powder. 
 
 No changes need be made in the guns, cannon, etc., 
 in order to employ guncotton, and it can be fired by 
 means of the ordinary percussion-caps. Another 
 useful property which it possesses is that it practically 
 does not foul or heat the guns at all, so that several 
 hundred charges can be fired from the same gun 
 without its having to be cleaned. 
 
 With the greatest respect, I have the honour to be, 
 My dear Baron, 
 
 Yours most truly, 
 
 C. F. SCHONBEIN. 
 BALE, 20ta June 1846. 
 
 This letter was laid before the Academy on the 9th of 
 September (the cause of the delay is explained in Ber- 
 zelius' answer), together with a communication of the 16th 
 of August from the second discoverer of guncotton, Prof. 
 Bb'ttger l of Frankfort on Main, and another from Wohler 
 of Gb'ttingen, and was printed in the Ofversigt, Arg. 3 
 (1846) p. 209. 
 
 1 Kudolph Bottger, born at Aschersleben in 1806, died at 
 Frankfort on Main in 1881. In August 1846, when professor 
 at the Physical Society at Frankfort, he independently dis- 
 covered guncotton, and joined with Schonbein in the practical 
 utilization of the discovery. 
 
88 LETTEKS OF BEEZELIUS 
 
 Eerzelius answered it as follows : 
 
 XIX 
 
 Berzelius to Schonbein 
 
 STOCKHOLM, 18th November 1846. 
 
 DEAR SIR, 
 
 The letter of June the 20th with which 
 you honoured me did not come to hand till the 
 beginning of September. Herr Merian, who was the 
 bearer of it, informed me that he was to deliver, 
 along with it, a packet of specimens of paper from 
 you ; this, however, he had left at Hamburg, and he 
 was unwilling to hand over the letter till the box had 
 come. But the box had, together with the rest of his 
 luggage, been sent to Berlin, whither he intended to 
 go in a few days. I requested him to deliver it to 
 our minister in Berlin ; this he failed to do, although 
 he made an ascent with the minister in Mr. Green's 
 balloon. As I also learned from him that you had 
 gone to England, I deferred expressing to you my 
 gratitude for the information on guncotton till I 
 learnt what your address was. I am now sending it 
 to London on the chance of its finding you. 
 
 Permit me to convey to you my sincerest congratu- 
 lations on this interesting and significant discovery, 
 the practical nature of which you have so promptly 
 
AKD SCHONBEIX 89 
 
 appreciated. Ever since Prof. Otto of Brunswick 1 
 suggested a method for obtaining guncotton, this 
 discovery has probably kept a greater number of 
 inquiring minds busy than any other in the field of 
 chemistry. 
 
 I also have been engaged in experiments . on it ; I 
 prepare it from equal parts by volume of concentrated 
 sulphuric acid and commercial nitric acid of specific 
 gravity 145. I have discovered that it is formed 
 from lignin, and can be produced from the lignin of 
 
 1 Friedrich Julius Otto, born in 1809 in Grossenhain in 
 Saxony, from 1835 professor of chemistry and pharmacy at the 
 Collegium Carolinum of Brunswick, where he died in 1870. 
 He also had, as he asserted, discovered a method of preparing 
 guncotton, founded on a paper by Pelouze [" Note sur les pro- 
 duits de 1'action de 1'acide nitrique concentre" sur 1'amidon et le 
 ligneux," Gompt. Rend., i. 7 (1838) p. 713]. This he had 
 published in the daily papers in October 1846, first in the All- 
 gemeine Zeitung of 5th October 1846 [reprinted in the Journal 
 fur prakt. Chemie, vol. xl. (1847) p. 194, and added superfluous 
 and malicious notes directed against Schonbein's legitimate 
 efforts to turn his discovery, the enormous practical value of 
 which he had instantly perceived, to the best pecuniary advan- 
 tage. These remarks were the more unjust as Schonbein was 
 actually suffering from the consequences of his " practical " dis- 
 covery. On September the 2nd, 1846, he writes to his wife 
 from London : " Perhaps I may make something of it if I do 
 not lose patience, but this is not easy. In certain respects it is 
 almost a misfortune to have made an important practical dis- 
 covery ; it completely destroys one's peace of mind. Faraday 
 and Grove told me the same thing : they continually stood in 
 fear of coming across something which would bring them in 
 contact with the practical world, as I have done." In October 
 he writes to her from Stanmore : " According to the opinion of 
 experts the patent is in no danger through Otto's articles. The 
 English press is unanimous in criticizing all later discoverers, 
 and saying that it is discreditable to these men to deprive me 
 of my well-earned deserts." 
 
90 LETTEES OF BEEZELIUS 
 
 all vegetable matter, especially if the incrustation is 
 previously removed by moistening it with a solution 
 of caustic alkali. I have prepared it from Sphagnum 
 palustre, from oakum, from straw, and, best of all, from 
 friable, decaying wood, which, when the humin has 
 been extracted by alkaline solutions, yields an exquisite 
 powdery guncotton. The scientific term I propose 
 to apply to it is lignin nitrate, since a body got from 
 these substances cannot well be called guncotton. 
 
 I also endeavoured to prepare it from Cladonia 
 rangiferina and Cetraria islandica. These, however, 
 contain a framework, which is composed not of lignin 
 but of starchy filaments, and yields nothing but 
 amylin nitrate, i.e., xyloidin. The products of com- 
 bustion of lignin nitrate comprise a gas which I think 
 is cyanogen, which I certainly had not looked for 
 among them. I had no time to inquire into the pre- 
 cise elementary structure of this interesting compound; 
 I dissolved it in caustic alkali, in which it is readily 
 soluble, and obtained therefrom saltpetre, glucinic 
 acid, apoglucinic acid and other products, which were 
 not examined further. My attempts to reproduce 
 lignin by means of the exchange of nitric acid for 
 water failed conspicuously. 
 
 You would greatly oblige 'me by favouring me with 
 the results of your further investigations on the appli- 
 cation of lignin nitrate as an explosive. 
 I have the honour to remain, 
 With the greatest respect, 
 
 Your most obedient servant, 
 
 JAC. BERZELIUS. 
 
AND SCHONBEIN 91 
 
 XX 
 
 Schbnbein to Berzelius 
 
 DEAR SIR, 
 
 Your kind note of November of last year has 
 just been forwarded to me from England, and so I 
 hasten to thank you most sincerely for it. I learned 
 with the greatest interest the results you obtained with 
 guncotton, especially as I also, as early as last spring, 
 made experiments not only with cotton but also 
 with a number of plants, consisting chiefly of lignin, 
 and obtained explosive substances from them. 
 
 You will have heard that last year, here in Bale as 
 well as in England, I carried out many experiments 
 in shooting and blasting with my guncotton, and I 
 should like now to give you some details. In 
 Faversham in Kent we employed a very accurately 
 constructed mortar, which throws shells of sixty-four 
 pounds and is used for testing the powder which the 
 factories of that place supply to the British Govern- 
 ment. Two ounces of the best English powder sent 
 a shell of sixty-four pounds from this mortar on an 
 average 275 feet, whereas an ounce of my guncotton 
 sent the same shell 550 feet. In carbines of narrow 
 calibre 10 grms. of guncotton produced the same 
 effect as 41 grms. of the best gunpowder. In pistols 
 of a particular pattern guncotton exhibited a driving 
 force seven times as great as that of gunpowder. I 
 made numerous experiments in blasting in the mines 
 and slate quarries of Kent and in a tunnel in our 
 
92 LETTEES OF BEBZELIUS 
 
 neighbourhood which is now under construction ; all 
 gave most satisfactory results, and in the opinion of 
 the engineers present proved that for blasting purposes 
 guncotton is preferable to gunpowder. One part of 
 guncotton is under these circumstances as effective as 
 five parts of powder. In many instances the gun- 
 cotton produced eight and ten times as great an 
 effect as powder. Although I experimented almost 
 daily for many months I have never had the slightest 
 accident and not once has any of the cannons, mortars 
 or small guns from which many hundreds of shots 
 have been fired under my direction, exploded. As far 
 as my own observations go I have not even observed 
 that the firearms were perceptibly damaged by the 
 guncotton. I once caused forty shots in succession 
 to be fired from an American carbine, and after the 
 experiment it was as clean as before. I find it con- 
 venient to saturate my guncotton with a solution of 
 potassium nitrate, for experience shows that guncotton 
 so treated is more readily compressible, without 
 becoming perceptibly harder to explode. Possibly 
 this film of potassium nitrate enveloping the explosive 
 filament makes it less easy to explode and more 
 uniform in action. In England they are now making 
 arrangements to prepare guncotton on a large scale, 
 and I think that there it will soon be widely used for 
 blasting. I and others also have not yet given up 
 the hope that guncotton will likewise be applicable 
 for purposes of war. It is anything but honest of 
 the French to continue to claim priority in the 
 discovery of guncotton on account of Bracconnot's 
 
AND SCHONBEIN 93 
 
 xyloidin as they have for some time done, especially 
 as they subsequently admitted the very obvious 
 difference between the two substances, and as I 
 prepared guncotton as early as last year. I had no 
 desire to assert my claims before the French Academy, 
 because I am convinced that impartial men of 
 science will come to a right conclusion on this 
 question. 
 
 The last number of Poggendorff's Annalen contains 
 a few papers of mine, which may interest you inas- 
 much as they indicate the facts which led me to the 
 discovery of guncotton. The resinous substance 
 which is formed by the action of a mixture of nitric 
 and sulphuric acids on sugar appears to be a substance 
 quite analogous to guncotton, and if the latter is lignin 
 nitrate, the former must be nitrate of sugar. Possibly 
 the names nitrolignin, nitrosaccharine, nitroamylin, 
 etc. would be suitable for such compounds. Since 
 according to my view N0 5 does not exist, I con- 
 sider that the compound in question contains ]N"0 4 
 combined with an organic substance. The following 
 fact which I have ascertained appears to be of 
 especial interest, namely that flowers of sulphur 
 treated with a mixture of nitric and sulphuric acids 
 produce sulphurous acid even at low temperatures. 
 Why is sulphuric acid not formed under these circum- 
 stances ? I hold the unusual view that the sulphurous 
 acid formed under these circumstances is a secondary 
 product, derived from the change of hydrogen sulphide 
 to peroxide, in a manner analogous to the formation 
 of sulphurous acid by the action of water on chloride 
 
94 LETTEES OF BEKZELIUS 
 
 of sulphur. Furthermore it is remarkable that 
 sulphurous acid brought in contact with the mixture 
 of nitric and sulphuric acids is not converted into 
 sulphuric acid, as takes place when the first hydrate 
 of nitric acid alone is mixed with sulphurous acid. 
 I think these reactions deserve the undivided attention 
 of chemists. That, according to my experience, ozone 
 combines with iodine, bromine and chlorine to form 
 compounds very similar to those which these three 
 bodies form with one another, is also a fact which 
 may not be without importance. 
 
 A few days ago I was most agreeably surprised by 
 receiving the Vasa medal. His Majesty the King of 
 Sweden has by granting this distinction bestowed on 
 me an honour of which I am hardly worthy, and for 
 which I feel myself deeply indebted to him. You 
 would be doing me a great favour if you would kindly 
 let me know whether I should express my humble 
 thanks for this distinction in a letter addressed to 
 His Majesty himself. 
 
 I trust that I shall soon have the pleasure of 
 receiving a letter from you, and I have the honour to 
 be, with the greatest respect, 
 
 Your obedient servant, 
 
 C. F. SCHONBEIN. 
 
 BiLE, 12th February 1847. 
 
AND SCHONBEIN 95 
 
 XXI 
 
 Berzelius to Schbnbein 
 
 STOCKHOLM, \Wi March 1847. 
 
 DEAR SIB, 
 
 I thank you sincerely for your courteous 
 letter of February the 12th and for the interesting 
 information which it contains. 
 
 I congratulate you cordially on the honour be- 
 stowed upon you by our king. It gave me great 
 pleasure to hear of it. His Majesty asked me what 
 should now be done with regard to your proposal to 
 communicate to us for a fixed sum the details of the 
 method of manufacturing guncotton, which has now 
 been made public. I suggested to His Majesty that 
 he should grant to the discoverer, whose invention 
 was certain to be profitable to us, some token of royal 
 favour, for instance the honour of knighthood. The 
 king replied that he would consider the matter. A 
 few weeks later a ceremony of investiture was held, 
 at which you, however, were not mentioned, although 
 several foreigners were named, and so I feared that 
 the subject had been overlooked, till I was most 
 agreeably surprised to learn from your letter that 
 His Majesty had not forgotten you. 
 
 At the last meeting of the Academy I submitted 
 your last letter to them. 
 
96 LETTEES OF BERZELIUS - 
 
 The king happened to be present at the Academy, 
 and to your memoranda added the reports on gun- 
 cotton given by his ministers from various quarters, 
 containing among other things a statement that in 
 Brunswick serious disasters had been caused by the 
 bursting of rifles through too powerful a charge of 
 guncotton. 
 
 Like you L. Svanberg 1 has prepared compounds of 
 sugar and gum with a mixture of nitric and sulphuric 
 acids; they are, however, not to be compared to 
 nitrolignin. You will observe that I have adopted 
 your nomenclature; lignin nitrate is in fact a mis- 
 nomer, for the substance which unites with nitric 
 acid is no longer lignin, as it has already given up 
 several atoms of hydrogen and oxygen. 
 
 On the other hand I am unable to subscribe to 
 your views on nitric acid and the nitrates. They 
 cannot be correct. The test of the truth of a theory 
 is that it should harmonize the particular instance 
 with the whole system of science ; for the laws of 
 nature are always consistent with one another. Now 
 if you advance a principle which makes an exception 
 of what was before consistent with scientific ideas, 
 logic pronounces against you. So far as I can judge 
 from your paper, you were led to this by concluding, 
 from the fact that ozone and nitric acid at ordinary 
 
 1 Lars Friedrich Svanberg, born in Stockholm in 1805, was 
 a lieutenant, then teacher of chemistry and physics at the 
 Military College at Karlsberg. From 1858 to 1874 lie was 
 professor of chemistry at Upsala, where he died in 1878. " Om 
 salpetersyrans forening nied nagra Kroppar," Ofversigt, Arg. 
 4 (1847) p. 51. 
 
AND SCHONBEIN 97 
 
 temperatures oxidize different bodies in an analogous 
 manner, that therefore the oxidizing constituent of 
 nitric acid must be ozone. In addition to this you 
 assume that ozone is a compound of H + 0, isomeric 
 with hydrogen peroxide, and so nitric acid must be 
 H 2 2 + N 2 4 and the nitrates, E N. But does ozone 
 really contain hydrogen ? This question we can 
 answer most emphatically in the negative. If oxygen 
 gas collected during the last third of its evolution 
 from potassium chlorate be exposed to a series of 
 short electric sparks, ozone is formed just as readily 
 and to precisely the same extent as during the first 
 third of the operation. In this case, however, it is 
 physically impossible for water to be present. This 
 constitutes the most indisputable proof that ozone 
 does not contain hydrogen. Hence it follows that 
 ozone is an allotropic modification of oxygen itself, 
 distinguished from the ordinary form by the sensation 
 it produces in the olfactory nerves and its power of 
 entering into all manner of combinations at low 
 temperatures ; thus ozone is entitled to an infinitely 
 greater attention than if it were an individual sub- 
 stance. From this point of view your discovery of 
 ozone is one of the most magnificent ever made ; but 
 you should not allow yourself to be dazzled by it. 
 
 Starting from this simple assumption, which is 
 now established, we have to ask what connection 
 there is between ozone and hydrogen peroxide, the 
 acids of nitrogen, chlorine, bromine, iodine, etc. 
 Ozone oxidizes at low temperatures and unites with 
 organic bodies to form derivatives which ordinary 
 
98 LETTERS OF BERZELIUS 
 
 oxygen is incapable of producing, as the latter only 
 becomes active at temperatures at which the organic 
 substances are destroyed. The acids I have mentioned 
 also produce]this effect ; they all give rise to oxygen 
 compounds at low temperatures. This shows that 
 hydrogen peroxide is not present in nitric acid. The 
 theory explains the formation of ozone by lightning, 
 by frictional electricity, and by hydro-electricity. 
 Its production by means of phosphorus then appears 
 of a purely catalytic nature, which is quite conceiv- 
 able: whereas it is not conceivable that so readily 
 oxidizable a body as phosphorus, which itself absorbs 
 oxygen, should yield so unstable an oxidation product 
 of hydrogen as]hydrogen peroxide. I trust you will 
 excuse my preaching, and not refuse to learn. Soon 
 you will find how the shadows are dispersed by the 
 light of ^correct ideas. 
 
 Address your letter of acknowledgment to the 
 Foreign Secretary, His Excellency Baron A. Ihre. 
 It is quite proper to enclose in it a message in an 
 envelope,- which, however, should not be sealed, 
 addressed to His Majesty the King, and to inquire of 
 the Minister whether he considers the letter suitable 
 to be delivered to His Majesty. This letter, however, 
 is not essential ; you need only request the Minister 
 to convey to His Majesty your respectful thanks ; 
 but perhaps it might not be unwelcome to His 
 Majesty^to receive a short letter from you. 
 Farewell. 
 
 Yours sincerely, 
 
 JAC. BERZELIUS. 
 
AND SCHONBEIN 99 
 
 XXII 
 Schonbein to Berzelius 
 
 DEAE SIR, 
 
 I thank you sincerely for your kind and 
 interesting letter of the 13th inst. I have followed 
 the advice you were so good as to give me and have 
 sent a letter of thanks to His Majesty the King, as 
 well as to His Excellency the Foreign Secretary. 
 Permit me in this matter to express to you my sincere 
 thanks for having obtained for me by your good 
 offices so honourable a distinction. 
 
 I can hardly assent to your and de la Rive's views 
 on the nature of ozone, although I readily admit and 
 have long been aware that they make it out to be 
 a substance of infinitely greater interest than it 
 appears according to my theory; for this reason I 
 wrote to de la Rive a short time ago : " For 
 ambition's sake I must wish that you and Berzelius 
 are in the right, and Mr. Schonbein in the wrong, 
 for ozone being mere oxygen modified by electricity, 
 would be a substance infinitely more interesting than 
 my peroxide of hydrogen." l My reasons for rejecting 
 your view are as follows: 1. Not a single fact is 
 known, which shows that any elementary body is 
 changed in any way whatever in its properties by 
 means of electricity. 2. On the other hand there are 
 a number of substances which by combining with 
 1 This sentence is in English in the original. Tr. 
 
100 LETTEES OF BEEZELIUS 
 
 oxygen modify it in such a way that it unites at 
 ordinary temperatures with many bodies, on which 
 pure oxygen, under the same conditions, has no action. 
 Such substances are for example HO, PbO, MnO, 
 AgO, which, when they combine with oxygen, so 
 change it that it decomposes potassium iodide, 
 converts -potassiuiq ferrocyanide into fsrricyanide, 
 colours guaiacum resin blue, etc. ; in other words it 
 acts like ozone. 3. When exposed to the action of 
 electric sparks for some time oxygen gas prepared 
 from melted potassium chlorate does, it is true, turn 
 starch paste containing potassium iodide blue, and 
 affects the organs of smell, but it is not, according 
 to my experiments, dissolved to any great extent 
 by solutions of potassium iodide or potassium ferro- 
 cyanide, or oxidizable metals ; and the residual gas 
 behaves like ordinary oxygen. Now I should think 
 that a cubic inch of dry oxygen gas if exposed for a 
 sufficient length of time to the electric current, 
 would be completely ozonized, and thus be entirely 
 taken up by the abovementioned solutions. 
 
 4. But infinitesimal traces of water vapour, such 
 as might be present in oxygen supposed to be dry, 
 suffice to produce a perceptible quantity of ozone, and 
 so it seems to me that some such view as mine is 
 less improbable than yours. 5. The destruction of 
 ozone on heating is readily explained by the assump- 
 tion that at higher temperatures it is split up into 
 water and oxygen, like so many other superoxides, 
 especially The'nard's oxidized water. According to 
 your view we must assume that heat restores the 
 
AND SCHONBEIN 101 
 
 ozonized oxygen to its ordinary condition. More- 
 over it would be strange if heat, which as a rule 
 increases the chemical activity of oxygen, should 
 produce the opposite effect on ozone. 6. In dry air 
 phosphorus has not the power to produce ozone in 
 appreciable quantities, but it forms it the more 
 abundantly, the more moisture is present. 
 
 With regard to the formation of ozone by means of 
 phosphorus, it appears to me that this fact is equally 
 remarkable whether we assume the former to be 
 modified oxygen or peroxide of hydrogen, for finely 
 divided phosphorus shaken up with an atmosphere of 
 ozone immediately destroys the latter. The forma- 
 tion of ozone in the presence of phosphorus must 
 strike us as equally strange whether we assume that 
 by means of catalysis modified oxygen or gaseous 
 hydrogen peroxide is formed, for the former should 
 be absorbed by phosphorus just as readily as the 
 latter should lose its active oxygen. I would take 
 this opportunity of drawing your attention to the 
 behaviour of ozone towards iodine, bromine and 
 chlorine. The compound formed when paper charged 
 with iodine is held in an atmosphere strongly charged 
 with ozone, is so like chlorine, that it shows almost 
 all the properties of the latter. It is not an acid, but 
 on treatment with water it is converted into iodic 
 acid and iodine. Similarly bromine and chlorine 
 water, which have absorbed large quantities of ozone, 
 are by no means acid, i.e., they do not contain chloric 
 or bromic acid. The same substance which ozone 
 forms with iodine seems also to result when strips 
 
102 LETTEES OF BERZELIUS 
 
 of iodine paper are exposed to moist atmospheric 
 air saturated with nitrous acid vapours, or suspended 
 in a flask, the bottom of which is covered with a 
 mixture of water and nitrous acid. 
 
 I suspect that there exists a compound consisting 
 of N0 2 -fH0 2 , which when it comes in contact with 
 iodine gives up to it its H0 2 . According to your 
 view we must assume that when ozonized oxygen 
 combines with iodine, bromine and chlorine it is as 
 ozone that it does so. 
 
 With regard to my views on the hydrate of nitric 
 acid, I venture to maintain that it is by no means 
 isolated and without analogy, so long as one holds 
 similar views on other acids. Anhydrous sulphuric 
 acid for example I regard as S0 2 + 0, the third 
 atom of oxygen being in a chemically active state ; 
 the hydrate of sulphuric acid I look upon as 
 S0 2 +H0 2 , and the normal sulphates as S0 2 +E0 2 ; 
 the hydrate of chloric acid would of course be 
 C10 4 +H0 2 , anhydrous iodic acid I0 4 +0 etc. 
 Possibly we might also regard the so-called first 
 hydrate of oxalic acid as 2CO-fH0 2 , acetic acid as 
 C 4 H 4 + 20 or as C 4 H 3 + H0 2 . However, I am always 
 suspicious about substances which cannot be isolated 
 and which cannot exist except in combination with 
 other substances, such as water and the so-called salt- 
 bases. I am half inclined to fear that the assumption 
 of these hypothetical compounds has retarded rather 
 than promoted the progress of chemistry. 
 
 I have taken the liberty of giving you some of my 
 views on the different conditions of oxygen in the 
 
AND SCHONBEIN 103 
 
 pages 1 which I enclose, and of submitting them to 
 your judgment. Should you consider them in any 
 way as worthy of your attention, I trust you will be 
 kind enough, when you have an opportunity, to send 
 me a few comments on them. Finally I must ask 
 you to do me a great favour. As the patent which 
 I have taken out for my guncotton in England will 
 undoubtedly be contested, I should be very much 
 obliged to you if you would state in a letter, in what- 
 ever manner you consider most suitable, that it was 
 I who first discovered and prepared nitrolignin. 
 Such an expression of your opinion would have great 
 weight in England, and I have little doubt that you 
 also will ascribe to me the priority in this matter. I 
 at any rate consider that I have a full claim to it. 
 With the sincerest hope that your valuable life may 
 be spared to Science, I remain, 
 
 With the greatest respect, 
 
 Yours respectfully, 
 
 C. F. SCHONBEIN. 
 BALE, 29th March 1847. 
 
 The letter of Berzelius no doubt suggested to a certain 
 extent a discourse of Schonbein's : " On various Chemical 
 States of Oxygen," 2 which he delivered on 21st April to 
 the Scientific Club of Bale, and in which he attacks the 
 views of Marignac, de la Rive, and Berzelius. [cf. Poggend. 
 Annal., vol. Ixxi. (1847) p. 517 ; where he uses the words : 
 " since the great Swedish chemist assails me in writing "]. 
 
 1 See Appendix. 2 Ibid. 
 
104 LETTEKS OF BEEZELIUS 
 
 Berzelius does not himself seem to have given any 
 summary of this work, for the passage in the Jdhresbericht 
 for 1848, * which treats of this paper, says with respect to 
 Schonbein's attempt to draw a parallel between ozone and 
 chlorine, bromine and iodine, and thus to represent them 
 as " oxylizations " of radicals not yet isolated : " all very 
 similar to views held thirty or forty years ago." 2 Berzelius, 
 the faithful adherent of the Murium theory, could not 
 have written thus. This view of mine is further con- 
 firmed by the fact that it can be proved that the report of 
 Schonbein's other work, for instance, on guncotton, 8 for 
 which, as we have seen, Berzelius evinced so great an 
 interest, was no longer drawn up by Berzelius himself, but 
 by Lars Svanberg. Consequently we may regard as the 
 last utterance of Berzelius on Schbnbein and his work a 
 passage to be found in the 27th volume of the Jahresbericlit y 
 which runs as follows : 
 
 " Assuredly there is at present no chemical investiga- 
 tion so important and so much wanted by the scientific 
 world as a systematic memoir of the history of ozone in all 
 its details. Certainly no work would yield such unexpected 
 results to any man who had the courage to undertake it in 
 earnest, and who did not try to avoid the difficulties by 
 means of vague phrases," 4 a practice to which Schonbein 
 was certainly not given. 
 
 On a sheet of paper in part filled with a draft of a letter 
 to Faraday which bears the address Rotzberg, near Stans- 
 stad, but no date, I have discovered the first hasty sketch 
 of an obituary notice of Berzelius, which, as the last 
 remark of Schonbein on his great colleague, may well have 
 
 1 " Jahresbericht iiber die Fortschritte der Chemie" continued 
 after the death of Berzelius by L. Svanberg. Presented to the 
 Swedish Academy of Science on 31st March 1848. [But 
 Berzelius did not die till 7th August 1848.] 
 
 2 Loc. cit. p. 1 2. 3 Loc. cit. p. 342. 4 Loc. cit. p. 29. 
 
AND SCHONBEIN 105 
 
 a place here, although it is unfinished. Whether it was 
 ever completed, or ever printed, I am unable to say, as I 
 have found nothing in any of the available journals with 
 which Schonbein usually kept up an active correspondence : 
 Allgemeine Zeitung, Morgenblatt fur die geUldeten Stande, 
 and the Easier Zeitung, which, as a local paper, must also 
 be taken into account. An obituary notice in No. 237 
 of the Allgemeine Zeitung of 24th August 1848 is plainly 
 not by Schonbein. 
 
 So far as I can read this hardly legible writing, the last 
 words of Schonbein on Berzelius are as follows : 
 
 "Jakob Berzelius is dead; his loss will be deeply 
 mourned wherever science is cherished and esteemed ; 
 for not only are we entitled to rank him with the most 
 eminent natural philosophers of the age, but he was 
 beyond doubt the first of all chemists that ever lived. 
 The lofty position which chemistry occupies to-day is due 
 to his investigations, which are as numerous and as 
 accurate as they are full of genius ; and without 
 exaggeration we may say that he has done more for the 
 advancement of science than all other chemists together. 
 The greatest and most brilliant service which he rendered 
 consists in establishing the law of the definite proportions 
 in which the elements combine with one another, a work 
 the enormous extent and significance of which only an 
 expert can appreciate. 
 
 " Like all truly great scholars he was devoid of petty 
 conceit and jealousy, and with an impartiality as great as 
 his knoAvledge he gave due recognition to the labour of 
 others, so that the whole chemical world gladly accepted 
 his verdict." 
 
 With this estimate of Berzelius by Schonbein I will 
 conclude. The opinions which we have heard the two 
 men express in their letters reflect as much honour on the 
 one as on the other. 
 
APPENDIX 
 
 ON VARIOUS CHEMICAL STATES OF 
 OXYGEN 
 
 ONE of the most important and interesting branches of 
 chemical investigation to which it would seem sufficient 
 attention has not been devoted is the influence exerted 
 on the affinity of a substance by the other substances 
 with which it is combined. In many cases the same 
 element in an isolated condition shows an essentially 
 different behaviour towards certain substances from that 
 which it exhibits when in combination. In this con- 
 nection oxygen of all simple bodies shows the most 
 remarkable behaviour ; for according as it is isolated, or 
 in this or that state of combination, it may show either a 
 very high degree of chemical activity or none at all, 
 
 If I am not mistaken there is no single element with 
 which dry oxygen combines at ordinary temperatures; 
 but when it is united with certain substances its be- 
 haviour is wholly different. Contrary to what theoretical 
 considerations would lead us to expect, combined oxygen 
 shows such a degree of chemical activity that even at low 
 
APPENDIX 107 
 
 temperatures it forms chemical compounds with a series 
 of bodies, on which free oxygen under conditions other- 
 wise the same has no action whatever. Among the 
 substances which by their union with oxygen raise its 
 chemical activity are several oxides of the general formula 
 RO, such as HO, PbO and MnO. When one of these 
 oxides combines with a further atom of oxygen bodies are 
 formed which have a remarkable power of oxidation ; for 
 example, they expel iodine from potassium iodide, convert 
 the yellow prussiate of potash into the red, turn guaiacum 
 solution blue, and destroy indigo solution. These com- 
 pounds also resemble one another in their voltaic be- 
 haviour; they possess a remarkable degree of electro- 
 motive power, i.e., they are eminently electro-negative. 
 The peroxides owe all these properties to their second 
 atom of oxygen. "We must therefore assume that this 
 second atom is in an essentially different condition from 
 the first. It seems to me that it would be desirable for 
 science to possess a term to distinguish the chemically 
 active oxygen in such a compound ; perhaps we might use 
 the expression " oxylized," by which I understand oxygen 
 which has a tendency to leave the substance with which 
 it is united in order to attach itself to some other oxidiz- 
 able body. Perhaps it would also be convenient to use 
 a special symbol such as to denote the oxylized atom of 
 oxygen in a compound. The peroxides of hydrogen, lead 
 and manganese would accordingly receive the formulae 
 HO, PbO Mn6. 
 
 As is well known, nitric oxide (N0 2 ) exerts a very 
 peculiar influence on the two atoms of oxygen which 
 combine with it to form nitrous acid. The condition of 
 the two oxygen atoms combined with N0 2 is not the 
 same as that of the second atom of oxygen in the per- 
 
108 APPENDIX 
 
 oxides mentioned above ; for anhydrous nitrous acid does 
 not act even on readily oxidizable bodies to any great 
 extent at ordinary temperatures, and can sustain a high 
 temperature without suffering decomposition. However, 
 these two oxygen atoms can without difficulty be con- 
 verted into the true oxylized state by mixing the nitrous 
 acid with HO. I have endeavoured to prove that the 
 hydrate of nitric acid is N0 4 + H0 2 , and that a compound 
 of the formula N0 2 + H0 2 also exists ; both are formed 
 on mixing N0 4 with HO ; the water, reducing a part of 
 the N0 4 to N0 2 , is itself converted into H0 2 , and this 
 peroxide combines partly with N0 4 and partly with X0 2 , 
 according to the following equation : 
 
 4 + 2HO = (N0 4 + H0 2 ) + (N0 2 + H0 2 ). 
 
 The oxidizing effects which these two bodies produce 
 at the ordinary temperature are, in my opinion, due to 
 the oxylized oxygen contained in their H0 2 ; since N0 4 
 binds H0 2 more closely than N0 2 does, K0 2 + H0 2 is a 
 more effective oxidizing agent than N0 4 + H0 2 ; hence 
 the former even when diluted with ever so much water 
 decomposes potassium iodide, potassium ferrocyanide, and 
 hydrogen sulphide with the liberation of N0 2 , whereas 
 very dilute nitric acid is unable to produce this effect. 
 
 As to chlorine, bromine and iodine, I regard them, in 
 accordance with the older theories, as peroxides of murium, 
 bromium and iodium, my opinion being that they contain 
 one atom of oxygen in the oxylized condition, to which 
 the remarkable oxidizing actions, which these bodies are 
 capable of producing at the ordinary temperature, must 
 be ascribed. Therefore I regard the oxides of murium, 
 bromium and iodium as analogous to those of water, 
 
APPENDIX 109 
 
 manganese and lead, etc., and ascribe to them the power 
 of oxylizing, not only one equivalent but the whole of the 
 oxygen with which they combine. 
 
 A peculiar interest attaches to the relations which exist 
 between chlorine, bromine and iodine, the peroxides, and 
 the so-called hydracids of the halogens. The first class 
 of substances show a great similarity in their voltaic and 
 chemical behaviour, a similarity which would lead anyone 
 who studied them without regard to the current hypo- 
 theses to believe that they had a similar chemical constitu- 
 tion ; this, however, is completely contrary to our present 
 ideas. What strikes me as especially remarkable is the 
 following : When the hydracids of these three halogens 
 are mixed with the peroxides, chlorine, bromine and iodine 
 are liberated ; furthermore it is well known that chlorine, 
 for example, partially converts lead oxide into lead per- 
 oxide. In fact it is not improbable that chlorine is able, 
 when in contact with water, to produce some hydrogen 
 peroxide. Moreover we know that concentrated nitric 
 acid immediately liberates chlorine from hydrogen chloride, 
 and my latest investigations have shown that even a very 
 dilute solution of nitrous acid, when added to hydro- 
 chloric acid, at once sets chlorine free. My hypothesis 
 compels me to explain all these phenomena in a different 
 way from that in which they are explained by our present 
 theories. When aqueous rnurium oxide is brought in 
 contact with a compound containing oxylized oxygen, 
 such as lead peroxide, a part of the murium oxide unites 
 with the oxylized oxygen to form murium peroxide, 
 while the remainder of the murium oxide or hydrochloric 
 acid combines with the lead oxide to produce the so-called 
 lead chloride. Conversely when murium peroxide is 
 made to react with lead oxide, a portion of the latter will 
 
110 APPENDIX 
 
 unite with the oxylized oxygen of the former to form the 
 peroxide, whereas another portion of the lead oxide 
 combines with murium oxide to form lead chloride. 
 Hydrochloric acid, in contact with concentrated nitric 
 acid takes up 6 from N0 4 + fi6, being oxidized to Mu6, 
 and this most probably unites with N0 4 to form an 
 unstable compound, which constitutes the oxidizing agent 
 in aqua regia. The action of murium oxide on N0 2 4- A 6 
 differs only in that the evolution of chlorine takes place 
 with greater ease. When electric sparks are passed 
 through a mixture of gaseous hydrochloric acid and oxygen, 
 chlorine and water are produced, as is well known. 
 According to my observations electricity determines the 
 combination of murium oxide with oxygen, and the latter, 
 by uniting with the oxide, is transformed into the oxylized 
 state. When a mixture of water vapour and oxygen gas 
 is subjected to the same electrical treatment, a hydrogen 
 peroxide is formed, namely ozone, and if the oxides of 
 lead, manganese, silver, etc., were capable of existing in 
 the gaseous form they would, when mixed with oxygen, 
 undoubtedly be transformed into their peroxides 011 
 passing electric sparks through them. Lead hydroxide 
 held before a point from which electricity is escaping into 
 moist oxygen or atmospheric air is, it is true, according to 
 my experiments, changed into its peroxide ; this is, how- 
 ever, due to a secondary reaction produced by the ozone 
 which is formed under these circumstances. 
 
 With regard to the chemical nature of ozone, the 
 highest authority on chemical questions now shares the 
 view first brought forward by de la Kive, that ozone is 
 nothing but oxygen modified by electricity, and that it 
 does not contain hydrogen. These chemists support their 
 view by the fact that electric sparks passed through 
 
APPENDIX 111 
 
 oxygen, prepared from melted potassium chlorate, produce 
 ozone. I am, however, unable to assent to this view for 
 reasons which I have explained elsewhere, chiefly because 
 there is not a single fact to show that electricity is capable 
 of changing in any way the chemical properties of any 
 elementary substance whatever. If oxygen is capable of 
 undergoing so extraordinary a chemical change under the 
 influence of electricity, this is a case perfectly unique, to 
 which there is not even the remotest analogy to be found 
 in the whole sphere of chemistry. On the other hand a 
 large number of cases are known which prove conclusively 
 that oxygen, when united to certain substances, acquires 
 so great a degree of chemical activity that it oxidizes even 
 at ordinary temperatures, and this analogy, it seems to me, 
 is more in favour of my theory as to the nature of ozone 
 than of those proposed by others. Therefore I am firmly 
 convinced that the assumption that oxygen prepared from 
 melted potassium chlorate still contains traces of water is 
 less bold than the view that ozone is an allotropic modifica- 
 tion of ordinary oxygen. As I have already stated, I shall 
 give up my theory and accept the one which I now 
 dispute so soon as anybody succeeds in transforming 
 into ozone by means of electricity a single cubic inch of 
 really dry oxygen. However, I may be wrong, and the 
 view of Berzelius and de la Kive may be correct. In 
 that case we should have to assume that the oxylization 
 which a number of substances can produce in oxygen 
 by combining with it can also be produced by electricity 
 alone, and furthermore that, for example, the second 
 oxygen atom of the normal peroxides exists in these 
 compounds as ozone, or that ozone and oxylized oxygen 
 are one and the same substance. Then we should have 
 also to assume that heat could, under suitable conditions, 
 
112 APPENDIX 
 
 reconvert oxylized into ordinary oxygen, since isolated 
 ozone is changed by heat into ordinary oxygen just as 
 the peroxides are reduced to the oxides under the same 
 conditions, the oxygen, thus separated, appearing in its 
 normal condition, and as the first hydrate of nitric acid 
 splits up into N0 2 , HO and 0. The separation of a 
 portion of nitric acid would in that case be due to the fact 
 that only a definite amount of ordinary oxygen is capable 
 of uniting with H, Pb, Mn, etc. If 6 in PbO is con- 
 verted into by the action of heat, then the oxygen 
 would split off, for PbO can remain united with 6 but 
 not with 0. According to the nature of the compound 
 RO, with which is combined, it requires a smaller or 
 greater amount of heat, to effect this change of into 0, 
 or its separation from KO. 
 
 In the case of HO this change takes place at moderate 
 temperatures, whereas lead peroxide requires a greater 
 heat and MuO a still greater. 
 
 As far as chlorine, bromine and iodine are concerned 
 regarding them as peroxides the highest temperatures 
 which we have as yet succeeded in producing are as 
 incapable of changing their into as they are of melting 
 charcoal or of decomposing a substance which is not a 
 compound. If, however, these peroxides are mixed with 
 substances which combine either with their oxide or with 
 their oxylized oxygen, then the decomposition takes place 
 with the greatest ease. 
 
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