ON THE DISCOVERY OF PALLADIUM A. M. W ~ T EUNIVERSIN . OF NORTH CAROLINA, CHAPELHILL, N. C.. AND H. B. FRIEDMAN. GEORGIA SCHOOL OF TECHNOLOGY, ATLANTA, GEORGIA
In 1803 there was circulated throughout the British scientific world a notice of a type almost unparalleled in the history of chemistry. That it would create much discussion was probably anticipated by its author, but he could not have foreseen the years of acrimonious debate, the bitter partisanship, and the ultimate disgrace of a prominent chemist that it produced. The notice read as follows (1): Palladium, or new silver, has these properties among others that shew i t to be a noble metal. 1. It dissolves in pure spirit of nitre, and makes a dark-red solution. 2. Green vitriol throws it down in the state of a regulus from this solution, as it always does gold from aqua regia. 3. If you evaporate the solution, you get a red calx that dissolves in spirit of salt or other acids. 4. It is thrown down by quicksilver, and by all metals but gold, platinum, and silver. 5. Its specific gravity by hammering, was only 11.3; but by flatting, as much as 11.8. 6. In a common fire, the face of it tarnishes a little, and turns blue, but becomes bright again, like the other noble metals, on being stronger heated. 7. The greatest heat of a blacksmith's fire would hardly melt it. 8. But if vou touch it, while hot, with a small bit of sulfur, i t runs as easily as zinc. It is sold by Mrs. Forster, a t Nu. 26, Gerrard Street, Soho, London; in samples of five shillings, half a guinea, apd one guinea each. An editorial in Nicholson's Journal (2) amplifies this somewhat: Mrs. Foster (Forster?), it appears, is only the vendor, and totally unacquainted with the person who brought the metallic substance and the printed paper to her house. . . . I received a small piece by the post. The piece of the specimen was a t the rate of about one shilling per grain. . .
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This strange announcement aroused the interest of Richard Chenevix,* one of the well-known chemists of his day. Chenevix was an Irishman, and of his early history little seems known (3). He was probably, however, educated as befitted a gentleman. Caught in Paris during the Reign of Terror, he was imprisoned by the Commune for some time. In the same 'Richard Chenevix was horn in Ballycommon. King's County, Ireland, in 1774. He was educated at the University of Glasgow. His parents were of French extraction, and much of Chcnevir's life seems to have been spent on the continent. The Royal Society elected him Fellow in 1801, and in 1803 awarded him the Copley Medal for his papers published in the Philosofikicd Transactions. In about 1804 he moved to France, where in 1808 he published a paper "Observations an the Mineralogical Systems," in which the views of Haiiy were upheld, and those of Werner attacked. Subsequently, Chenevix turned to literature, writing several novels, plays, and poems. He died in Paris on April 5, 1830 (4).
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cell with Chenevix was an unnamed French chemist, who whiled away the time by explaining to his cell-mate the principles of chemistry. The interest thus aroused induced Chenevix, upon his release, to study the subject in earnest, and by 1803 he had attained the distinction of Fellowship in the Royal Society and in the Royal Irish Academy. Best known as an analytical chemist, his work on corundum and sapphire had created favorable comment. Immediately on learning of palladium, Chenevix undertook the experimental verification of the claims advanced in the notice, for, as he said in a letter to Vauquelin, professor of chemistry in Paris (5): Nothing is discussed here in the scientific world save palladium. Everyone received, some days ago, printed notices like that I am sending you; as soon as I had read it, I went to the seller and purchased all that was available (332 grains for 15 guineas). I have found since that the properties described in the notice are accurate. . . . I am sending you a little piece with this notice that you may see for yourself what it is. . . . To this Vauquelin adds: I have repeated, on the small piece I received from M. Chenevix, the experiments cited in the notice, and have found them accurate. . . . It seems from these oroverties that this is an element and different from , , those w c kr~ow,hut before allinning this definitely, the experimrnts must I ~ n n t i v l i l . Thr work that. 11. C'henevixk undertakine ', at this moment should Githout doubt decide this question. . . . ~
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After considerable work, Chenevix presented the results of his researches before the Royal Society, in a paper entitled "Inquiries concerning the Nature of a metallic Substance lately sold in London, as a new Metal, under the Title of Palladium" (6). As Chenevix said: The mode adopted to make known a discovery of so much importance, without the name of any creditable person except the vendor, appeared to me unusual in science and was not calculated to inspire confidence. It was therefore with a view to detect what I conceived to he an imposition, that I procured a specimen and undertook to learn its properties and nature. I had not proceeded very far, when I perceived that the effects produced by this substance, upon various tests, were such as could not he referred, in toto, to any of the known metallic substances. I immediately returned to Mrs. Forster, and became possessed of the whole quantity. I could not obtain any information as to its natural state, or any trace that might lead to a probable conjecture. The substance had been worked by art: i t has been rolled out in flatting mills; and was offered for sale in specimens consisting of thin laminae. The largest of them were about three inches in length, and half an inch in breadth, weighing on the average 25 grs. and were sold for one guinea The other laminae were smaller in proportion to the price.
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Chenevix then discussed at length the tests he had applied to the palladium. He admitted that the properties described in the notice were correct, except for a slight error in the specific gravity, but was still unconvinced that palladium was an element. A new series of experiments was undertaken in an effort to synthesize palladium, using platinum as a base. As Chenevix reported: We have been told of extraordinary anomalies in chemical affinities, by M. Berthollet; and Mr. Hatchett has made us acquainted with some, not less extraordinary in the properties of alloys. Yet I think we shall cease to wonder a t what has been related by these chemists, when we learn that palladium is not, as was shamefully announced, a new simple metal, but an alloy of platina, and the other substance which can mask the most of that metal, while i t loses the greater number of characteristic orooerties . its own, is mercury. I confess that i t was not from an analysis of ~alladiumthat I was first led to this result; for I had convinced mGself, by syntheses, of its nature, and had formed the substance, before I could devise any - vrobable method of ascertaining its component parts. A
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In other words, Chenevix was so convinced that palladium was not an element that he searched until he devised an alloy whose properties closely resembled those of palladium. By altering the proportions of mercury and platinum, the properties of the alloy could be varied, and he found no test for mercury in the resultant material. The conclusion reached was that: There is not any property of this compound which appears to me so wonderful as that which is manifest by tfiese experiments. It is a striking proof how unfounded was the opinion of some philosophers, who supposed that the rapidity of combination was a measure of the force of affinity. We do not know of any affinity among chemical bodies which is more powerful than that of platinum and mercury appears to be. The obstacles which must be overcome to fix the latter metal are oroof of this: yet thr difficult\. of forming this comhination to its fullcxtrnt i> extrrmc. . . . Palladium also brines to our rccollcction a contemntiblc fraud directcd against science: theYname, therefore, should not b'e admitted. I have called it an alloy. . . . Chenevix's article created quite a sensation, and was widely reprinted. The synthesis of palladium became a popular pursuit in continental laboratories. As the following editorial indicates, the work received immediate acceptance (7):
It appears, then, from Mr. Chenevix's experiments that this pretended simple metal is a combination of platina and mercury; and it must excite not only astonishment, but humility in the alltivation of natural knowledge, to find that a combination of two metals, each upon so high a specific gravity as those which are combined in palladium, should produce a compound, the specific gravity of which is less than that of the least weight of the component substances; and, moreover, that mercury whose affinity for
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caloric had hitherto been found to baffle all attempts to destroy its volatility; could, when combined with platina, become as fixed as any metallic substance with which we are acquainted. But nature laughs a t our theories, and forces us from time to time, by extraordinary discoveries of this sort, t o acknowledge that we are her vassals, and that we strive in vain to bring her within our laws. A note of doubt crept in, however, for there appeared shortly after an editorial in a French journal (8): Certainly this material shows new and singular properties, for the . . . experiments performed by the Citizen Vauquelin on the small piece of metal sent by M. Chenevix show the presence of neither platinum nor mercury.. . . I t was not long until reports of investigations in France and Germany began to cast grave doubts on the accuracy of Chenevix's work. Klaproth wrote that he could not agee with this synthesis (9). Vauquelin and Fourcroy (lo),unable to find mercury in palladium or to synthesize the substance, suggested that perhaps it might be an alloy of platinum and some new element. Joseph Hume (11) wondered if tungsten were not involved. While the discussion was a t its height, there appeared in Nicholson's Journal another anonymous notice, fully as strange as any of the preceding (12): REWARD OF TWENTY POUNDS FOR THE ARTIFICIAL PRODUCTION OF PALLADIUM
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The following is a copy of a paper received by me under cover, by the two-penny post. It is written in the same hand as a note which covered a small piece of palladium mentioned to have been received by me last midsummer. . . . Upon inquiry, I find that Mrs. Forster has received the sum of £20 with instructions conformable to this paper. . . . Sir, As I see it said in one of your journals, that the new metal I have called palladium, is not a new noble metal, as I have said it is, but an imposition and a compound of platina and quicksilver, I hope you will do me justice in your next, and tell your readers I promise a reward of £20 now in Mrs. Forster's hands, to anyone that will make only 20 grains of real palladium, before any three gentlemen chymists you please to name, yourself one if you like. That he may have plenty of his ingredients, let him use 20 times as much quicksilver, 20 times as much platina, and in short of anything else he pleases to use: neither he nor I can make a single grain. Pray be careful in trying what it is he makes, for the mistake must happen by not trying i t rightly. My reason for not saying where it was found, was, that I might make some advantage of it, as I have a right to do. If you think i t fit to publish this, I beg you to give the names of the umpires, as I have desired Mrs. Forster to keep the money until next mid-
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summer, and to deliver it only in case they can assure her that the real metal is made by a certificate signed by you, and by them, on this check. I hope that a little bit of whatever is made may be left with Mrs. Forster. In the next issue of the journal, Mr. Nicholson wrote as follows (13): In consequence of the ultimatum received by the anonymous paper of which a copy is in the last number of this Journal . . . I waited upon Mrs. Forster, who personally assured me that she holds the sum of twenty pounds (which was paid to her by the same unknown person who placed the palladium in her hands), under the trust or engagement to pay the same to the bearer of the certificate mentioned on the said paper, a t any time before midsummer next; and that, if not claimed during that time, she shall afterwards consider herself a t liberty to repay the money when demanded by the same unknown person. I have therefore requested Charles Hatchett, Esq. F. R. S. and Edward Howard, Esq. F. R. S. to join myself as judges of the product which may be made in our presence, agreeably to the before-mentioned paper; to which proposal they have consented. At this point it is necessary to introduce another character, one who is destined to play a very important r8le in the events that are to come. William Hyde Wollaston,* M.D., F.R.S., was educated a t Cambridge, from which university he received a degree in medicine. Like Chenevix, his transfer to chemistry was largely fortuitous. Upon quitting Cambridge, Wollaston's application for some hospital post was rejected in favor of a man whom Wollaston cbnsidered less able than himself. Disappointed, disgusted, and in financial dYEculties, he abandoned medicine in favor of chemistry, and by 1804 had attained great prominence. On June 24, 1804, Wollaston read before the Royal Society a paper entitled "On a New Metal, Found in Crude Platina" (14). The new metal was rhodium. However, Wollaston also mentioned that he had been able to separate a small amount of palladium from the same platinum ore. After outlining a method of separation, he went on to say: The propcrties of palladium that hare been enumerated undoubtedly belong to none oi thc simple substances that wc arc acquainted with; and 'William Hyde Wallaston was born in East Dereham, Norfolk, England, an August 6, 1766. He was educated as a physician, in Caius College. Cambridge, receiving the degree of Bachelor of Medicine in 1788, and that of Doctor of Medicine in 1793. He was elected a Fellow of the Royal Sodety on March 6,1794. He abandoned the practice of medicine in 1800, and turned to research in many fields cf science. I n all, fifty-six papers were published by Wollaston. Chemistry was but one of his many interests, for his works include papers on pathclogy, crystallography, astronomy, optics. electricity, mechanics, botany, mineralogy, and physiology. Of particular interest to chemists is his work in support of Dalton's atomic theory, on gas explosions, and on the refractameter and the goniometer. During his later life, Wollaston was suhject to attacks of partial blindness, caused by the brain tumor which ultimately produced his death on December 22, 1828.
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no experiment that I have made, has tended to confirm the suspicion of its being a compound, consisting of any known ingredients. Theexperiments above related show evidently that the ore of platina contains a very small quantity of palladium; and it is not unlikely that this may have been a constituent part of some of the compounds obtained by Mr. Chenevix, and may have misled him, by some properties which he would consequently observe, into the suspicion that he had formed palladium. I t isnot, however, without having repeatedly endeavored to imitate his experiments, that I have ventured to dissent from such authority. I made WIL~~A HYDE M WOLLASTOU many atteml;ts to unite (From a steel engraving in Muspratt's "Chrmistry pure platina with meras Applied to Arts and Manufactures"-1860.) cury, by solution, and by amalgamation; but without success in any one instance. From a solution of platina, carefully neutralized as Mr. Chenevix directs, with red oxide of mercury, and mixed with a solution of green sulfate of iron, I indeed obtained such a precipitate as Mr. Chenevix described; but upon examination of these flakes, they yielded mercury by distillation; and the remainder consisted of platina combined with a portion of iron, but had not any of the properties which I could suppose owing to the presence of palladium. . . . Meanwhile, Chenevix prepared a rebuttal to the attacks on his work. Reviewing the voluminous literature which had sprung up on the subject of palladium, he said (15):
It was natural to suppose that a subject so likely to spread its iduence throughout the whole domain of chemistry, and which tended even to the subversion of some of the elements, would awaken the attention of philosophers. We find, accordingly, that it has become a subject of enquiry in England, France, and Germany; but the experiments which I had recommended as least likely to fail have been found insufficient to insure the principal result; and I have had the mortification to learn that they have been generally unsuccessful.
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Stoutlydefending himself by further experiment, and insisting that palladium is an alloy, Chenevix added:
I do not exaggerate the number of attempts I made during this time . . . in stating them to have been one thousand. Among these I had four successful operations.* Palladium must indeed be difficult to synthesize if but four out of a thousand tries are successful! In a postscript, the following remarks are appended: Since this paper was written, Dr. Wollaston has published some experiments on platina. He has found that palladium is contained in very small quantities in crude platina. . . . Whatever be the quantity of palladium found in a natural state, no conclusion can be drawn as to its being simple or compound. Nothing is more probable than that nature may have formed this alloy. .
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The reward of twenty pounds was never claimed, and was presumably withdrawn as specified in the notice. Another letter to the editor of Nicholson's J o u m l now appeared, in which the author of the preceding anonymous communications disclosed himself, thus clarifying in part the turbid waters of the dispute. It read as follows (16): February 23, 1805
SIR: The candour with which you communicated all circumstances that came to your knowledge concerning palladiurd, a t a time when the discoverer of that substance was yet unknown to you, demands my earliest acknowledgements, as having been the author of those communications; and it is proper that I should also express the satisfaction I received on learning the respectable tribunal you nominated a t my request, for examining the merits of any attempts that might be made to form the substance artificially. As I have already shewed (in a paper which you did me the honour to reprint in your Journal last, page 34), by what means a very small quantity of palladium may be extracted from the ore of platina, and as I have there examined the synthetic attempts t o prove that the body was a compound, with a degree of attention which I thought due to the chemical skill of the person who proposed them, as well as to the degree of uncertainty that must attend a subject entirely new; I cannot now adduce further chemical evidence and can only add, for the information of those whose judgment has been biassed by the difficulty of accounting for the production of so large a quantity of palladium as was offered for sale, that a proportional quantity of platina, from which the whole was extracted, was purchased by me a few years since, with the design of rendering it malleable for the different purposes to which it is adapted. That object has now been attained, and during the solution of it, various unforeseen appearances occurred, Tnoms THOMSON, Phil. Soc. Glosgow, 3, 139 (1850), says that Chenevix spent about fourteen hours a day in the laboratory during this time.
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some of which led to the discovery of palladium; but there were other circumstances which could not be accounted for by the existence of that metal alone. On this, and other accounts, I endeavored to reserve to myself a deliberate examination of these difficulties which the subsequent discovery of a second new metal, that I have called rhodium, has since enabled me to explain, without being anticipated even by those foreign chemists, whose attention has been particularly directed to this pursuit. I remain, Sir, Your obliged and obedient Servant, W. H. Wollaston. So Wollaston was the author of the strange notices! Wollaston, the aloof, dignified Secretary of the Royal Society, had presented to the world this discovery in such an unorthodox manner. Again the scientific world buzzed, and letters like the following were dispatched (17): The secret of palladium is discovered. M. Wollaston . . . has confessed that he is the discoverer of it. . . The experiments already performed, are, he thinks, sufficient to characterize i t as a new metal. M. Chenevix will naturally object that palladium can still be made of the platinum found in the mineral from which it was extracted, and from the mercury used in the separation. . . . On July 4, 1805, Wollaston read before the Royal Society a paper entitled "On the Discovery of Palladium; with Observations on other Substances found with Platina." No comment was included on the unusual mode of publishing his discovery, nor was Chenevix mentioned. This ended the subject of palladium as far as Wollaqton was concerned. He apparently lost interest in the matter, and his subsequent work was in other fields. This, then, is the story of palladium as it appeared in the journals of the day. It is interesting, however, to try to dig beneath the surface and to speculate on the motives and reasons back of these strange events. In Wollaston's case, these seem clear. Upon leaving Cambridge, Wollaston was very short of money. A means of replenishing his purse was essential. From his knowledge of the chemical inertness of platinum, he concluded that if it could be purified and fabricated, i t would make an ideal material for constructing laboratory ware. He therefore invested in a large amount of crude platinum, a t that time not an expensive material, and commenced research which ultimately enabled him to produce malleable platinum. The process for preparing platinumware was kept secret, and exploited by Wollaston for financial gain. An added inducement to secrecy was the peculiar action occasioned by the two new elements, whose chemistry Wollaston wished to work out for himself. Early publication would tend to damage Wollaston's monopoly of the platinumware business, and would further disclose to the world the existence of these peculiarities in behavior of crude platinum.
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As certain other chemists were already hot on the trail of new elements in the platinum group, Wollaston chose the anonymous letter as a means of obtaining priority without making full disclosure, or, as he said in the first notice: "That I might make some advantage of it, as I have a right to do." Viewed today, it is evident that Chenevix was badly mistaken in his opinions regarding palladium. This may have been due to either or both of two factors: first, the strange mode of announcement led him to suspect a hoax, from which conviction he could never liberate himself; once he had taken his stand against palladium, he was unwilling to withdraw from his position. In the second place, as Wollaston suggested, it is quite possible that Chenevix, not knowing that palladium occurred with platinum, actually isolated some palladium from the platinum he was using in his attempts a t synthesis, and was thus misled into-the belief that he had produced it artificially. During a t least the latter part of this dispute, Wollaston was Secretary of the Royal Society, and as such it must have been his duty to present the papers of the Society and to enter them in the minute book. It seems strange that he should have permitted Chenevix to publish his work, knowing i t to be wrong. Thomas Thomson, a friend of both men, explains this in his "History of Chemistry" (3):
It is very much to be regretted that Dr. Wollaston allowed Mr. Chenevix's paper to be printed, without informing him, in the h s t place, of the true history of palladium, and I think that if he had been aware of the bad consequences that were to follow, and*that i t would ultimately occasion the loss of Mr. Chenevix to the science, he would have acted in a different manner. I have more than once conversed with Dr. Wollaston on this subject, and he assured me that he did everything he could, short of revealing his secret, to prevent Mr. Chenevix from publishing his paper; that be had called upon, and assured him, that he himself had attempted his process without being able to succeed, and that he was satisfied that he had fallen into some mistake. As Mr. Chenevix still persisted in his conviction after repeated warnings, perhaps it is not vety surprising that Dr. Wollaston allowed him to publish his paper, though had he been aware of the consequences to their full extent, I am pursuaded that he would not have done so. It comes to be a question whether, had Dr. Wollaston informed him of the whole secret, Mr. Chenevix would have been convinced. Wollaston, his reputation enhanced by the discovery of palladium, became a more and more prominent figure in the science of chemistry; Chenevix, his reputation destroyed and his career blasted, withdrew from the scene of his defeat, and was heard of no more.
Literature Cited
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Phil. Tram.. 93, 290 (1803). ( I ) CRENEYTX, (2) ANON., NiChDlson's I.. 5, 136 (1803).
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(3) T~ormrsTHOMSON,"History of Chemistry," Vol. 2, London, 1831. 4 ANON.,Genl2eman's M a p i n e . 100, 563 (1830). Ann. chim. phys. [I]46, 333 (1803). (5) CHBNBVIX, (6) CHENEVIX,Phil. Trans., 93, 290 (1803). (7) ANON.,Nicholson's J., 5, 136 (1803). (8) ANON.,Ann. chim. phys. [I146, 337 (1803). (9) KLAPROTK, ibid. [I]49, 256 (1804). (10) V A W Q ~ LAND I N Fomcnou, ibid. 111 49, 217 (1804). (11) H m , Phil.Mag., 19, 29 (1804). (12) ANON.,NiChoLon's I.,7, 117 (1804). (13) NICHOLSON, ijid.. 7, 159 (1804). (14) WOLLASTON, Phil.Trans., 94,419 (1804). (15) CHBNBVIX, ibid., 95, 104 (1805). (16) WOLUSTON,Nkholsm's I., 10, 204 (1805). (17) ANON..A m . chim. phys. [I]54, 198 (1805).
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