Electroplating the Platinum Metals AN HISTORICAL REVIEW OF THE EARLY RESEARCHES By Peta D. Buchanan Imperial College, London The successful development of gold and silver plating in 1840 led to a number of scientists turning their attention to the electrodeposition of platinum and palladium, but before commercially satisfactory pro- cesses could be established they met with considerable difficulties because of th? insolubility of the anodes and of the complex nature of the chemical compounds of these metals. The introduction of gold and silver plating in severe technical problems. These were the 1840s naturally prompted the study of the nevertheless tackled with enthusiasm by a electroplating of platinum and palladium. It number of scientists in England, France, was at first assumed that platinum, having so Germany and Russia and attempts to develop a many similar properties to those of gold, would reliable process continued throughout most of be equally amenable to electrodeposition, but the nineteenth century until satisfactory unfortunately its insolubility as an anode and standards of quality were achieved-a veritable the complex chemistry of its salts presented triumph of hope over experience. John Frederick Daniel1 1 790- I845 The vcr? earl? attempts at alcrtroplating zwrf’ grad? handirappcd 113 thp lack of a satisfa( tnr% hatter? until Professor J F 1)anipll of King’s Collcgc~, London, devisad his self-polarisinp rc.11 uhich Pnahlrd thin hut uniform roar- inps to h(> df>positPd In this reproduction nf an earl) Ilaguwrotrpe in the poAsrssron of rht. Uo7ul Institution h~ is wen, on th(Jlf,tt, dwnonstraring his nru hattwr to Foradar, to uhom hr had drsrrihcd it in 11/36 as “a twltaic combination whirh I trust )nu uill think worth3 of the rmmp of thP CO\ S r4 \ T RATTrR I”’ KeproduLed bv LOLIT~S%ot rhe Koval Inwrurion 1 ondon Platinum Metals Rev., 1981, 25, (11, 3241 32 Interest in electroplating began in the late an improvement on the Daniell Cell, but in 1830s, but at this time a reliable source of con- discussing those two he wrote: tinuous current was lacking: large and powerful “I found that although the batteries of Daniel1 voltaic piles were built in the early years of the and Grove were admirably contrived instru- century but these were quite unsuitable for an ments, yet it is very desirable to possess one that electroplating process which required a low could be set in action at a moment’s notice, and with comparatively little trouble. ‘l’he platinised voltage applied at a steady rate over a consider- silver battery is peculiarly suitable for the able period. Due to local action the voltaic cell operator, for when it is in action it complerely rapidly declined in strength. These early talks to its possessor. If the current is very feeble researches, particularly on the electroplating of a faint murmur is heard; if a moderate current is passing it hisses; but if a violent one it roars. At gold, have been reviewed by Hunt (I), who this present moment I have nineteen batteries at refers to the major steps forward taken in I 836 work in the same room where I am writing and when Professor J. F. Daniel1 of King’s College, they are each telling me the work they are perfor- London, described the first self-polarising cell ming” (7) or constant battery which enabled thin but He had earlier, in a paper on the battery uniform coatings to be deposited (2). given to the Royal Society of Arts for which he was awarded their Gold Isis ,Medal, made some- thing of a disclaimer: The Pioneer Work of Alfred Smee “I wish it to be clearly understood that it does not possess the absolute constancy of Daniell’s, or It was one of Ilaniell’s students in the the intensity of Grove’s battery” (8) chemistry department at King’s College who took up the study of electroplating and who An amusing aside on this point was made some years later by Clerk Maxwell, who was madc a major contribution to the subject. Alfred Smee entered King’s in 1834, gaining a rather given to composing humorous verses, silver medal for chemistry. Both his grandfather and who composed an “electric valentine” and his father had been employed at the Rank beginning: of England, the father becoming Chief “Constant as I)aniell, strong as (;rove; Accountant in 1831 (3). At that time the Chief Ebullient through all its depths like Smee; Accountant lived with his family in an official My heart pours forth its tide of love, And all its circuits close in thee.” (9) residence in the Bank, the necessary security confining them at home in the evening hours. Smee’s battery relied upon his observation On leaving college young Alfred therefore set that an electrode having a roughened surface up a laboratory in a room leading out of the caused the hydrogen formed during the reac- family drawing room and next to the ledger tion to disperse, preventing the build-up of a office and here, working alone with elementary film of bubbles. His cathodes were either of equipment, some lent by Daniell, he carried out silver etched with acid or of platinum abraded a remarkable series of experiments in with sandpaper, both being placed in a cell con- electrochemistry (4). taining “nitro-muriate of platinum” as the His first self-imposed task was to devise a electrolyte. This produced a thin layer of battery more suitable for work in electrodeposi- platinum in the form of a black powder, yield- tion, and on February 28th, 1840 he was able ing an electrode simply and cheaply and one to read a paper to the Royal Society, “On the unaffected by the strength of acid in any cell. Galvanic Properties of the Metallic Elementary Banks of cells could be employed varying “from Bodies with a description of a new Chemico- the size of a tumbler to a 1 o to I 2 gallon vessel”. Mechanical Battery” (5). Shortly before this Its success lay, however, in its simplicity, and it another type of battery had been introduced by aroused great interest in the art of depositing K’. R. Grove (4), and Smee considered this to be one metal upon another. Platinum Metals Rev., 1981, 25, (1) 33 Alfred Smee 18 18-1877 Born in Camberwell, educated at SL. Paul’s School and King’s College, London. and then trained as a surgeon at St. Bartholometo’s Hospital, Smee carried out all his resrarches in etectroptating in a room set aside for him in the Bank of England whcrc his father lived as Chief .4ccountant. He was electc?d a fr4ou: of the Royal Society in 1840, the year in which he published his ’‘l?lr,menfs o.f Elertrometallurgy, or thr ,4rt of Working in Metals by thc. Galvanic FLuid”, at the age of 22 By the end of 1840 Smee, still only 22 years “Platinating metals by the galvanic current is a old, had compiled and published a remarkable new feature in science. The prwess is similar in all respects to gilding but is more difficult. The text book, “Elements of Electrometallurgy”, a solution of the nitrwmuriate of platinum must be term he himself coined. Dedicated to the Prince very weak, and the battery must be charged with Consort, who, with Queen Victoria, had been dilute acid. The object to be coated must be very shown some of Smee’s specimens of electroplat- smooth, and thoroughly cleansed by potash, before the process is commenced. Having ing, the first edition was soon exhausted and a proceeded thus far, and the solution of platinum second and much larger edition was published being ready, a very fine platinum wire, in connec- in parts during the year 1842 while a third tion with the silver of the battery, must be placed so as to dip into the solution, but must not be revised and enlarged edition appeared in I 85 I immersed beyond a very short distance. The following upon a French translation published object to be platinated is now ready for connec- in 1845. tion with the zinc of the battery, after which is In his first edition Smee described his effected, it is to be dipped in the solution. Immediately, oxygen gas will be given off from processes for both platinum and palladium the platinum wire, in connection with the silver. plating, writing that: From the copper or other metal to be platinated, no gas will be evolved, provided too much “Hitherto the reduction of these metals, in any electricity be not generated. In a few minutes the other state than that of the black powder, has object will be coated with platinum. During the been always considered impossible.” process, the object should be withdrawn from He claimed that processes for “platinating and time to time, and rubbed over with a little whiting. The colour of the metal thus reduced is palladiating” rested upon the authority of his so similar to polished steel that it would be book and went on: difficult to distinguish the one from the other. It Platinum Metals Rev., 1981, 25, (1) 34 is needless to say that it has a beautiful the same year a special post, somewhat appearance. It would be of great Galue as a honorary in its duties, was created for him in coating for telescopes, microscopes, quadrants, and a hundred other articles which must be the Bank of England. exposed to the action of the weather.” (TO) For palladium plating Smee used a similar Surgeon to the Rank of England electrolyte, nitro-muriate of palladium with a This appointment was made largely upon the palladium anode: recommendation of Sir Astley Cooper, the dist- “This metal is whiter than platinum, but not inguished surgeon, who was a friend of Sir John so bright as silver.