William Hvde Wollaston J THE PRODUCTION OF MALLEABLE PLATINUM By Donald McDonald Johnson Matthey & Co Limited

The occurrence of the bicentenary of true facts brought to light, by the long and Wollaston’s birth affords an opportunity to painstaking work of the late Mr L. F. Gilbert, review in these pages the important scientific who devoted many years to a study of the and technical work that he did in the field subject but unfortunately died before he of the platinum group of metals. The physical could collate and publish the results in full. and chemical details of that work are of He was, from 1919 to 1955, a lecturer in course well known from his published papers chemistry at University College, London, and to the Royal Society, including the Bakerian his papers are in the custody of its Library, Lecture of 1828 which he prepared just before but have not so far found an editor to prepare his death. But, until recent years, little was them for the publication for which those known about the circumstances in which he interested have hoped. He did, however, in undertook and carried on the work and a 1952 publish a short paper on Wollaston’s number of legends have grown up about it. work on platinum in The Notes and Records These have latterly been dispersed, and the of the Royal Society which, together with a

William Hyde Wollaston 1766-1829 Born 200 years ago, Wollaston loas the jirst to refine native platinum on a logical and scientijic basis and to develop its industrial use. In the course of his researches he also discovered palladium and rhodiunr. This article describes the circumstances in which Wollaston undertook and carried on his work andputs his achievements into proper perspective with those of his predecessors and collaborators (Portraitfrom a mezzotint by W. Ward, A.R.A., in 1824, oj a painting by J. Jackson, R.A.)

Platinum Metals Rev., 1966,10, (3),101-106 101 long correspondence over many years with popular in his district and had a full pro- the writer of this article, helped to disclose a gramme of social engagements, but still number of facets of the affair. It is possible found time for the study of nature. In 1797 therefore to incorporate a good many of his friends persuaded him to move to the Gilbert’s conclusions here. wider scope of London and then, in 1800,to Wollaston was born in Norfolk on August the surprise of everyone:, he threw up his 6th, 1766, the third son of Francis Wollaston practice and retired from medicine. and his wife, Althea Hyde. His father was an astronomer and one of his uncles a well-known Work with Smithson Tennant doctor, William Heberden; both were Fellows His reasons for doing this have been much of the Royal Society. His main schooling was debated but there seems to be no reason to at Charterhouse (1774-78)and in July 1782 doubt his own statement that mental anxiety he was admitted to Gonville and Caius about his patients caused him excessive and College, Cambridge, to study medicine with painful distress. At the same time there a view to making a career in it. He graduated had opened for him some hopes of being able M.B. in 1787 (M.D. in I793), was awarded a to make beneficial use of his experience in Fellowship and stayed on for two years. chemical research, which he was tempted to While there, he met fellow students with develop in association with his friend interests in the pure sciences and became Smithson Tennant. The latter had also attracted by their work. He tried his hand at prepared himself to practice medicine but he astronomy and botany, but it was Chemistry too had given it up, though for reasons dif- and physics that appealed to him most and in ferent from those that affected Wollaston. 1786 he took up serious study in them under Tennant was casual in his approach to life Isaac Milner. In this course he was no doubt and had inherited sufficieiit money to support stimulated by his friendship with Smithson himself; Wollaston was serious and steadfast Tennant, a well-to-do young Yorkshireman but had to earn his living:. The combination who had been at Christ’s reading chemistry of the two had the promise of being effective and botany since 1782, and had just (1786) and they duly came together for business, transferred to Emmanuel, and was already turning their attention to the preparation of (1785)a Fellow of the Royal Society. He was platinum for commercial and scientific use, a five years older than Wollaston and had been subject that had already attracted the atten- to the Continent and met leading chemists tion of both in the laboratory. there. This experience had made him a clever To explain their reasons for choosing it experimenter and Wollaston was fascinated and to emphasise the importance of their by the results. He did some work himself in work, it is necessary to give some attention his own rooms and in the laboratory of his to past history. Until well into the present brother, Francis, also studying at Cambridge, century it was generally believed that and so were laid the foundations of his Wollaston alone was the pioneer in making scientific knowledge and the openings for his platinum available for fabrication. The own genius in experiment. leading chemical textbook of the turn of the In 1789 he moved to London to forward century (Roscoe and Schlorlemmer) mentions his medical studies by attending lectures and a few earlier names but gives little indication walking the hospitals and eventually, in 1792, that their work was of any importance; he took up practice at Huntingdon. This nothing was then known about Tennant’s lasted only a few months and he moved to part in the business until Gilbert discovered Bury St Edmunds, where he stayed until it in the 1930s through access to the accounts. 1797, becoming qualified as a Fellow of the On the other hand, Wollaston’s scientific Royal College of Physicians in 1793. He was results were completely documented in the

Platinum Metals Rev., 1966, 10, (3), 102 Bakerian Lecture. But in this he makes little once sought. These concentrated on dis- reference to his predecessors, none to his solving the mineral in aqua regia, precipitat- collaborators and none to the use to which his ing the platinum with sal-ammoniac, calcining process was put. He did however in another this to a sponge of platinum metal, heating place make a public statement that he made this to the highest temperature possible and no claim to have originated it, but merely to then forging the product. This too was have improved its details. developed in France by a series of dis- tinguished chemists of whom the last, Platinum Fabrication de Milly, communicated the details to Fausto before Wollaston de Elhuyar in Spain, who had been en- Native platinum was first brought to the couraged by his Government to study possible notice of European scientists in 1748 after uses for this Spanish-American product. occasional rumours of its existence in New Don Fausto soon produced a workable Granada. As soon as samples were available process (1786) in conjunction with a French a number of well-known chemists got to colleague, Pierre Chabaneau, but had then work upon it and by 1760 a great deal had to go to other duties, leaving the latter to put been found out. Naturally its powers of it to commercial use. A laboratory-factory resistance to melting at the highest tempera- was set up for him in Madrid and between tures then available and to corrosion by all 1786 and 1804 a considerable amount of the simple acids soon gave rise to hopes of refined malleable platinum was turned out in using it. The French chemist Baum6 pro- ingots, jewellery, objets d’art and chemical duced evidence that it could be consolidated apparatus. A surviving example of the work by forging at a high temperature like iron, of Chabaneau’s silversmith Francisco Alonso but it was soon found that when this was is the splendid 55-ounce platinum chalice applied to the grains of the native metal they dated 1788 given by the King of Spain to often failed to cohere. This was due to the Pope Pius VI and preserved in the Treasury fact that the mineral contained a small at St Peter’s, Rome. quantity of alloyed iron and, at the very high temperature used, this oxidised to a surface Empirical Methods film of magnetite. To secure bonding, there- It is apparent therefore that considerable fore, this iron must be removed. The first quantities of reasonably good malleable process used was a scorification of the mineral platinum had been prepared and used well with an oxidising mixture of potash and white before 1800. But the methods used were arsenic. This not only removed the iron, purely empirical, the product varied in but yielded a molten eutectic product that quality and sometimes failed mechanically. could be cast into thin discs from which, There was no real fundamental knowledge of by careful heating just below the melting the composition of the native mineral or of the point, the arsenic could be volatilised and the nature and properties of the products derived resulting medallion forged to good malleable from it. At its best, the principal one reason- metal. This method was exploited by the ably satisfied a need and no notable progress French goldsmith Janety over the period was made until Wollaston and Tennant 1786 to 1812 and by its aid he made jewellery, decided to seek it. crucibles and other laboratory ware. The In 1798 in London the newly founded principal example of his work that has sur- Philosophical Mugazine published an English vived is the four original Standard Metres, translation of some recent French work on all of which are still preserved in Paris. platinum by the Abbe Rochon and this The arsenic process was slow, painful and revived in England an interest in the metal dangerous, and alternative methods were at that had flagged since the classic work of

Platinum Metals Rev., 1966, 10, (3), 103 Lewis forty years earlier. At least three its industrial uses, According to Gilbert, at people were stimulated to do some work the beginning they shared expenses until on the subject. The first was Richard Knight, earnings began to come in to help with them. who sent a paper to the Philosophical Magazine Profits did not appear until 1809 but then in 1800 on a new method for making the improved rapidly; Wollaston as working metal malleable. In it platinum sponge was partner was allowed 10 per cent of income prepared as his predecessors had done but, before the rest was equally divided. The before forging, he compressed it by hand- partnership continued until Tennant's death pressure into a white-hot mould and only in 1815, after which Wollaston continued the applied the hammer after this had been done. work alone until 1821 when it seems to have The second interested party was William ceased. In all, from 1800 to 18z1, about Allen, the famous pharmacist who, with a 47,000 troy ounces of native platinum were young assistant named Thomas Cock, took treated and nearly 36,000 ounces (over one up the study a year or two later. This ton) of malleable platinum obtained. The resulted in the production of some crucibles first operations were purely scientific. Be- in 1805 but nothing was known about the tween 1800 and 1803, 7000 ounces of native methods until Cock published them in 1807. metal were dissolved in aqua regia and Then it was disclosed that the sponge metal Wollaston devoted himself to an intensive was now pressed in a cold mould, first by examination of the solution, while Tennant hammering and then by means of a screw inquired into the relatively small quantity press. Only after that was heat applied and of insoluble black material which had forging begun. This method was later applied hitherto been dismissed as 'graphite'. The industrially by Cock's brother-in-law, Percival result was that Wollaston discovered pal- Johnson, the founder of Johnson Matthey & ladium and rhodium, and Tennant iridium Co. Meanwhile the third interested party in and osmium. This cleared the way for work 1800 comprised Wollaston and Tennant. on the solution and, by February 1805, five They entered into a loose partnership to crucibles had been made and sold, the price investigate thoroughly native platinum from being 5s per ounce. But the really important the scientific point of view and then to develop sales came from a new use introduced by

One of Wollaston's note- books, open at the page recording the discovery of palladium. A note on the facing blotting paper reads: '' The upper part ofopposite page WQS written July 1802. I believe the C meant Ceresium a name which Z once thought of giving to f'alladium." The notebook is now in the possession of the Department of Miner- alogy and Petrology of the University of Cambridge

Platinum Metals Rev., 1966, 10, (3), 104 The powerful horizontal press designed and used by Wollaston to compress his platinum into cakes before forging. It may now be seen in the Whipple Museum of the History of Science at Cambridge Wollaston, namely, the manufacture of boilers low heat to produce platinum sponge. He for concentrating the weak sulphuric acid, emphasised that the heat must be only just produced by the chamber process, to oil of enough to bring this about and, in any vitriol. Between 1805 and 1818 there were grinding required, the metal must on no sixteen of them, weighing from 322 to 427 account be burnished. He recognised the ounces (24 to 47 wine gallons) at prices up to need to preserve in the sponge a certain E4oo. Nearly 7000 ounces of metal were sold virginity about its surfaces if the subsequent in this form, against 1300 ounces for crucibles, welding was to be successful. A century and Gilbert gives a surprising figure of 17,000 later his acumen in this respect provided a ounces as going to gun-makers, ostensibly vital foundation for the science of powder for touch-holes but probably for decoration metallurgy. Having got his sponge into a as well. fine and uniform powder by hand-rubbing, he washed and elutriated it thoroughly with Wollaston’s Process water. After pouring off the excess of this, As mentioned above, Wollaston published he transferred the metal mud to a brass a full account of the technical details of his mould and then closed tlis with a steel stopper process just before he died in 1828. The wrapped in blotting-paper and topped with essential points are that the aqua regia used some wool, which allowed the excess water for dissolving the mineral should be dilute to escape under hand-pressure, A plate of (about 50:so) to avoid dissolving the iridium. copper was then put on top and the whole The yellow precipitate produced by sal- introduced into a powerful horizontal press amoniac was to be well washed and then of his own design. This produced a hard well pressed, before being gently heated at a cake of metal which was next exposed to the

Platinum Metals Rev., 1966, 10, (3), 105 Wollaston’s use of platinum in boilers for the concentration of sulphuric acid opened up the Prst jield of employment of the metal on a relatively large scale. This invoice was for his second boiler, weighing 423 ounces and made in 1809 for R. Farmer & Son, Oil of Vitriol Manufacturers, Ken- nington Common

greatest heat that he could obtain and then “his discovery of the malleability of platinum forged by hand on an anvil. An ingot of it has been asserted, alone produced about about 20 oz of malleable platinum resulted ~30,000”, and this story has been freely and this could be hammered into sheet or exploited by later writers. Gilbert, with his drawn into wire. Such was the material access to Wollaston’s accounts, reduces the which Wollaston and his fabricators used for figure by about half, and that from all his their articles for sale. He himself used the full business activities. It does seem, however, procedure throughout the rest of his working that he did achieve his object of financing life, but his successors never took up the wet his research activities by means of this work. part of the process, preferring to follow Gilbert describes its scope as extending Knight and Cock in compressing the sponge “inter alia to optics, astronomy, crystal- in a dry state before forging it. Perhaps for lography, mineralogy, electricity, mechanics, this reason the properties of their metal were physiology and pathology, nearly all his clear never quite as good as Wollaston’s, but and concise papers giving useful, often nevertheless it was good enough to satisfy classical, additions to knowledge”. He inven- their clients until well into the present cen- ted valuable optical instruments, gave early tury. The rest of his discoveries they were support to the new atomic theory, and made very pleased to adopt, and the platinum important discoveries in the directions of fabricating industries of both England and stereochemistry, spectroscopy, electromag- France used them to improve their existing netic induction, refrigeration, photography methods. But really it was not until a century and the above-mentioned powder metal- after Wollaston’s start of his work that the lurgy. Charles Babbage said of him that in real significance of his investigations into the his mind there was “a plain and distinct properties of the surface of powdered metals line which separated what he knew from what was grasped and applied to the beginnings of he did not know”, and “that his predominant powder metallurgy. principle was to avoid error”. His contribu- In his obituary notice in the Gentleman’s tion to the advancement of science was a very Mugazine of 1829 the statement is made that large one.

Platinum Metals Rev., 1966, 10, (3), 106