early scientific enquiries into the properties and nature ... · in mind that casanova did not...

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Early Scientific Enquiries into the Properties and Nature of P latinum

“ Upon the w ho le this S e m i - m e ta l see ms a very- s ingular B o d y that mer i ts an exacte r In q u iry into its Na ture than hath hi ther to been made. ”

W I L L I A M B R O W N R I G G

T he first p la t in u m to be subjected to scientific investigation by E u ro p ean scientists cam e to England, b ro u g h t hom e in 1741 by C harles W ood from Jam aica . Earlier sam ples h ad reached E urope in one way or ano ther , par ticu larly th ro u g h Spain, b u t beyond being regarded as a curious substance with som ew hat rem arkab le properties, no pub lished work was done u p o n them. T h u s Charles W ood m ust be given priority since his sam ples led to full scientific examination, identification and publication .

W hen this book was first pub lished very little was known ab o u t W ood, bu t as a result of the exhaustive genealogical researches of his g rea t-g rea t-g ran d so n M r. M. H. W ood some details of his life an d activities b ecam e availab le to the original au th o r in 1965 an d formed the subject of a pub lished p a p e r (1). C harles was b o rn at W olverham pton , the sixth son of the famous W illiam W ood (1671-1730), an ironm aster an d a m a n of g rea t en terp rise am o n g whose undertak ings w as the m aking of coppe r co inage for b o th I re land a n d the A m erican Colonies - a work th a t b ro u g h t u p o n him a vitriolic a t tack by D ean Swift.

In 1729 W illiam Wood, w ho enjoyed the p a tro n ag e of the Prim e M in iste r Robert Walpole, together with two of his sons, F rancis and C harles, p ro m o ted a com pany financed by public subscrip t ion to es tablish an iron works at Fris- ington near W hitehaven in C u m b er lan d an d there to p roduce m alleab le iron by smelting with coal. W illiam died in the following year an d by 1733 the en terp rise had collapsed, leaving the two sons b an k ru p t. A ru ined a n d d isappo in ted m an, Charles W ood went off to C aro lina for a time, re tu rn ed to C u m b e r la n d w here he m arried in 1735, an d then settled in J a m a ic a where the first child of the m arr iag e was born in 1739. H ere he seems to have engaged in m etal m in ing of som e kind, and he certain ly practised as an assayer. H e has been described by a n u m b e r of

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“A History of Platinum and its Allied Metals”, by Donald McDonald and Leslie B. Hunt

© 1982 Johnson Matthey

^ illiam Brownrigg 1711-1800

\ n a t iv e of C u m b e r l a n d . B ro w n r ig g c o m b in e d a d i s t i n g u i s h e d sc ien tif ic c a r e e r w i th a m o d e s t a n d re t i r in g n a tu r e . After t a k i n g his M.I). in L e y d e n he s e t t l ed d o w n to p ra c t i c e m e d ic in e in W h i t e h a v e n a n d was e le c ted a Fellow o f the Koval Socie ty in 1742. H e b e c a m e f r i e n d ly with C h a r l e s VI oo d . w ho p a s s e d to h im the s p e c i m e n s of p l a t i n u m , b u t a l th o u g h B ro w n r ig g la te r c a r r i e d ou t o n e o r two e x p e r i m e n t s on t h e m he p a s se d th e m o n to t h e Royal Soc ie ty fo r f u r t h e r e x a m i n a t i o n

From a portra it pa in ted in about 1790

formerly in the Board Room of the

hitehaxen H ospita l

writers as the Assay Master to the Jam aican Government at this time, but the post was not in fact created until 1747. More recently, however, research by Mr. Robert Barker in Jam aica (2) has established that Wood again spent some time there and that he was appointed the first Assay Master in that year, several pieces of Jam aican silverware m ade during the period 1747 to 1749 showing his assayer’s mark, C.W.

During his first period there some samples of native platinum had reached Wood from Cartagena, no doubt from a smuggler, and on his return to England in 1741 he passed them on to William Brownrigg, a doctor practising in Whitehaven who had published the results of a number of researches on subjects ranging from the gases found in mineral waters and the problem of “ fire dam p” in coal mines to the purification of common salt, his papers being presented to the Royal Society by his friends in London. Nothing was apparently done with these specimens until W ood’s final re turn to England on giving up his appointment in 1749, when he set up w ith others an iron forge at Low Mill, near Whitehaven. Renewing his friendship with Brownrigg, whose brothers-in-law were among the investors in the Low Mill enterprise, Wood now persuaded him

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to exam ine the samples of p la t in u m an d to u n d er tak e a few experim ents upon them.

In the m eantim e, p resum ab ly in his labo ra to ry in K ingston, J a m a ic a , W ood h ad carried out some exam inations of his own, finding th a t the m eta l was present in small w hite shot-like gra ins am ong a black m agnetic san d and th a t it could be m elted only after mixing with m ore fusible m etals such as copper, silver and tin. H e subm itted the native m etal to cupella tion w ith lead an d found no altera tion in either its behaviour or its weight, while it also w iths tood a twelve-hour digestion with nitric acid.

T h e specimens th a t W ood b ro u g h t hom e with h im were well chosen to show the essential facts about the metal. T h e y consisted of:

XII. Several Papers concerning a new Semi- Metal, called Platina; communicated to the Royal Society by Mrt Wm. Watfon F. R. S.

The covering letter from Dr. William Brownrigg, read to the Royal Society by William Watson on December 13, 1750. W ith this he enclosed a n u m b er of samples of n a t iv e p l a t i n u m "‘first presented to me about nine years ago” and an account of the preliminary experiments carried out by Charles Wood and himself. In his second letter Brownrigg described Wood as “ a skilful and inquisit ive metallurgis t who is not ambitious to a p p ea r in p r in t"

E x tra c t o f a L e tte r from W illiam Brownrigg M . T>. F. R . S. to W m. Watlbn f . R . S.

‘D ear Sir, ff'bitfhavm, Die. 5 , 1 7 5 0 . Rt*d Dec. 13 Y T A K E the Freedom to indofe to you

*75°- an Account o f a Semi-metal call'd T lo tin a d i Pinto-, which, fo far as I know, hath not been taken notice o f by any Writer on Minerals. Mr. H ill, who is one o f the moft modern, makes no mention o f it. Prcfuming therefore that the Subjeft is new, I requcft the Favour o f you to fay this Account before the R oyal Society, to be by them read and publilhed, if they, think it defcrv- ing thofe Honours. I fhould fooner have publiihcd this Account, but waited, in hopes o f finding Lei- fure to make further Experiments on this Body with fulphureous and other Cements 5 alfo with Mercury, and fcvcral corrofive Menjirua. But thefe Experiments 1 fhall now defer, until I learn how the above u receiv'd. The Experiments whicn I have related were fcvcral o f them made by a Friend, whofc Ex- attneis in performing them, and Vcncity in relating them, I can rely on : However, for greater Certainty, I (hall m yfelf repeat them I am, dear Sir,

Tour moft obedient Servant,

W. Brownrigg.

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illiani Vi atson 1 7 1 5 - 1 7 8 7

The English physician and scientist well known for his researches on electrical phenom ena. Elected to the Royal Society in 1741. W atson was a most active Fellow as well as a founder m em ber of the Royal Society Club, and enjoyed a wide circle of f r iends among con tem porary scientists. It was to him that Brownrigg passed the samples of p la t inum , with an accompanying letter on his pre lim inary findings, for p re sentation to the Royal Society. In the last year of his life he received a knighthood for his services to science

1 Platinum grains m ixed w ith b lack sand (m agnetite)2 Native platinum grains separated from the sand3 Platinum that had been fused (after alloying)4 A piece of such fused m etal fashioned into part of the pom m el of a sword

Brownrigg carried out a few p re lim inary experim ents on the native p la t inum , including unsuccessful a t te m p ts to b r ing ab o u t either its fusion or its cupella tion with lead, an d then dec ided to pass the specimens on to the Royal Society together with a n account of W o o d ’s experim ents an d of his own views on the m ater ia l an d its occurrence. H is friend W ill iam W atson , a distinguished physicist and a m em ber of the R o y a l Society, was asked to m ake the p re sen ta tion a n d this he did on D ecem b er 13th, 1750, ad d in g some com m ents of his own to B row nrigg ’s con tr ibu tion (2).

In the first letter Brownrigg d esc ribed how he h ad com e into possession of the sam ples of p la t in u m and went on:

“ It is found in considerable q uan tities in the Spanish W est Indies (in what part I could not learn) and is there known by the nam e of P latina di Pinto. T h e Spaniards probably call it Platina from the resem blance in colour that it bears to silver. It is bright and shining, and of a uniform texture; it takes a fine polish, and is not subject to tarnish or rust.”

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After describing his few experim ents he concluded:“ It appears that no known body approaches nearer to the nature of gold, in its m ost

essential properties of fixedness and solidity, than the sem i-m etal here treated of; and that it also bears a great resem blance to gold in other particu lars.”

W o o d ’s first wife h ad died a n d in F eb ru a ry 1756 he m arr ied B row nrigg ’s widowed sister J e m im a a n d then in 1765 moved from C u m b e r la n d to South W ales where he built a n iron works a t C arfa rfa nea r M e r th y r Tydfil. T h is grew in im portance to become the largest of its t im e in W ales a n d here W o o d spent his last years an d died in 1774.

Before leaving C harles W ood, however, there m u s t be repo rted a curious isolated incident th a t has com e to light from an entirely unexpected source, namely T h e M em oirs of Casanova. T h e reference is to a visit p a id by C asanova in 1757 in Paris to a wealthy w om an, the M arq u ise d ’Urfé, w ho was in terested in alchemy an d the occult an d h ad expressed a wish to m eet him. In the course of the visit she took h im to her alchem ical labora to ry an d showed h im a vessel con taining som e pla tine del Pinto which she was abou t to convert into gold . . .

“C ’était M . Vood en personne qui lui en avait fait présent l ’année 1742 .”

H e was shown the p la t in u m resisting the ac tion of su lphuric , nitric and hydrochloric acids separately bu t yielding to a q u a regia. She was m elting it by m eans of a bu rn ing-m irro r , saying th a t alone it could not be m elted otherwise, which show ed it to be superior to gold. She also show ed h im how it was p re c ip itated by sal-am m oniac, “ w hich has never been able to p rec ip i ta te g o ld ” . No further exp lana tion of these s ta tem ents has so far em erged b u t it m ust b e borne in m ind th a t C asanova did not ac tua lly write his m em oirs until 1792 an d by that t ime most of the facts ab o u t p la t in u m were know n an d h ad been widely published. (4)

William W atson’s ContributionsAfter reading B row nrigg’s le tter to the Royal Society, giving all the details of W o o d ’s experim ents, W atson read a fu r ther co m m u n ica t io n of his own, quo ting as m entioned in the preceding chap te r , the im p o rtan t passage from U llo a ’s

journal. T h e Presidential C h a ir w as still occupied by M a r t in Folkes, who together with W a tso n h ad befriended Ulloa du r in g his confinem ent in L ondon in 1746. T h e n in the following F eb ru a ry he was asked to read to the Royal Society a fur ther le tter from Brownrigg (3) in w hich the w ri te r disclosed for the first time the nam e of C harles W ood an d went on to describe his expe rim en t to show tha t p la t in u m did not resist the ac tion of lead in cupe lla tion as he h a d p re viously thought.

As one of his b iographers has w ri t ten (5), while B ro w n rig g ’s ac tua l co n tr ib u tion to ou r knowledge of the properties of p la t in u m was not p e rh ap s of m ajor importance, he none the less p layed a vital role in th a t the p u b lica t io n of his

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Shortly a f t e r r e a d i n g Brovvnrigg’s l e t t e r s a n d a p a p e r of his o w n to the Koval Societv W a t s o n w ro te two le t te rs to his f r i e n d P r o f e s s o r Bose in W i t ten- b e rg g iv ing ail a c c o u n t o f t h ese earlv in v e s t ig a t io n s o n p l a t in u m . Bose i m m e d i a t e l y p u b l i s h e d t h e m in G e r m a n , w i th th e h e a d in g " A Newly D isco v ere d M eta l in S o u th A m e r i c a ” , a n d they s e r v e d to a r o u s e c o n s i d e r a b l e in t e re s t a m o n g c h e m is t s t h r o u g h o u t E u ro p e . T h i s sho w s th e o p e n i n g p a g e o f W a t s o n 's first l e t te r o f J a n u a r v 1751

findings brought them to the notice of scientists throughout England and continental Europe. Possibly his most significant comment was that quoted at the head of this chapter.

William Watson played a large part in this dissemination of knowledge. In January 1751 he wrote an informative letter to his friend Georg Matthias Bose (1710-1761), Professor of Natural Philosophy at the University of Wittenberg, with whom he had been in constant correspondence on the new subject of static electricity. Bose immediately published the letter in German in the first number of a journal on popular science, Physikalische Belustigungen, just established by Christopher Mylius in Berlin (6 ). A second letter from Watson followed in May of the same year in which Watson apologised for the delay in answering Bose’s letter of acknowledgement of February 20th, this being occasioned by the death of the Prince of Wales (Frederick, elder son of George II, a most popular prince, had died of pneumonia on M arch 31st at the early age of forty-four) and in which he gave more details on platinum and referred to Ulloa’s published work. He also mentioned that it takes a high polish and suggested its use for the mirrors of telescopes.

These two letters aroused considerable interest among chemists throughout Europe as many comments to this effect confirm in the literature. One example, written many years later by the great French chemist Antoine Francoise de Fourcroy, is typical:

“These first attempts, which announced very extraordinary properties, made a great commotion in Europe, at a time when the discovery of a metal as singular as this appeared to be was a phenomenon entirely unexpected. Then the great chemists of Europe set to work on platinum and its distinctive properties.” (7)34



Scheffer’s Researches in SwedenIn the m iddle years of the eigh teen th cen tu ry there w as a very active in terest in the sciences in Sweden. A country rich in m inerals , it p ro d u ced a n u m b e r of d is tinguished chemists a n d metallurgists, anxious to s tudy these deposits a n d to identify the metallic elements they contained. Beginning w ith G eorg B ran d t the list includes J o h a n n Gottschalk W allerius, H enrik T heoph il Scheffer, Axel Fredrik C ronsted t, T o rb e rn O lof Bergm an, Karl W ilhelm Scheele an d J o h a n n Gottlieb G ah n , all extremely well know n for their con tr ibu tions to early m etallurgical science.

In 1733 B rand t discovered cobalt a n d carried out a system atic investigation of arsenic a n d its com pounds; in 1751 C ronsted t discovered nickel in a m inera l from a cobalt mine, while Scheffer, in the sam e year, m ad e a m ajo r co n tr ib u tio n to our early knowledge of p la tinum .

H. T . Scheffer s tud ied at the University of U ppsa la , w here he learn t m athem atics from A nders Celsius, b u t as there was th en no course available in chemistry he en te red the M ining College, w here his fa ther was secretary, at the age of tw enty-one a n d becam e one of B ra n d t ’s m ost enthusiastic pupils. H e also established a private labora to ry for analytica l work. For ten years from 1739 he was m anag ing a m ine an d a m etal works p roduc ing copper an d a little gold bu t the enterprise d id not succeed an d in 1749 he re tu rn ed to Stockholm to w ork in the M ining College a n d also as a n assayer a t the M int, while in a d d it io n h e gave lectures in chem istry . H e was elected a m em b er of the R oyal Swedish A cadem y of Sciences in 1746 a n d published a n u m b e r of pape rs in the ir t ransac tions . By far the most im p o rtan t of these, however, was his co n tr ib u tio n to the discovery of p la tinum in 1751.

It has been m entioned in C h ap te r 2 th a t D on A ntonio de Ulloa, after his adventures a n d his re tu rn to M adrid , h ad been com m issioned by King F erd inand VI to under take a mission th ro u g h o u t E urope to s tudy scientific developments a n d in the au tu m n of 1751 he was for som e weeks in Stockholm. Here he was welcomed by the Swedish scientists and , at a m eeting of the Academy on O c to b e r 12th, he was p roposed for m em bersh ip by the secretary, Pehr W ilhelm W argen tin , also an as tro n o m er an d m a th em a t ic ian who w ould have known of U llo a ’s work, an d he was duly elected.

W hether or not he met Scheffer a n d discussed p la t in u m w ith him is not known, bu t it is most likely that, in seeking out those w ho could advise h im on science and industry am ong the small n u m b e r of scientists in Stockholm, such a meeting took place.

However th a t m ay be Scheffer, u n d oub ted ly p ro m p ted by Ulloa or by the letters from W atso n to Bose or possibly both , very soon p roduced a p ap e r for the Academy, su b m itted on Novem ber 19th a n d read on the 28th, w ith th e title “ T he W hite Gold or Seventh M etal, ca lled in Spain ‘P la tina del p in to ’, Little Silver of Pinto, Its N a tu re D esc ribed” (9). In this he records th a t in J u n e 1750 he received a sandy spec im en conta in ing “ flat t r ian g u la r scales, w hite as silver” tha t were not a t t ra c ted by a m agnet, th a t the sam ple h ad been o b ta in ed from

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<D e t h v ita G n llc t , eller j j t tn d e M e ta lle n . kaUadtiSp.it/ic-H , Platina del P in to , *Pintos

jm ä S t i f te r , b e jk r if v i t t i l f in n aturA f

H E N R . T H E O . S C H E F F E R .0

Ar i 7 f o i J u n i M."nad, fick ja g a f H e r r AiTcs-

f o r R i DF.NsKoi.Den m ork f a n d , hvilken H e r r Affefforcn hade futt i S p a n ie n , m ed

den underra t te lfe , at den vore if ran V a l l - In dien.

Denna fand beltod i a f m o rk a fä m -k o m . 2 . a f jarn-targade Jarnmalms k o r n , hvilka drogos a f M agneten . 3 . a f fa gedigna gullkorn . 4 . a f flata fcalena T r ia n g la r , hvita fora S ilfver , h v i l k a M a gne ten aldeles icke drog.

D e (Ta trekantifja M etal l-fm ulor fyntes vara J e r n , hvilket a f n 'g o t tilialle hade b i ifv i t h v i t t utan uppäj men d e t bciynneriigafte v a r , at det ickc drogs a f M a g n e te n , fall än de t v a r fa fmi- d i g t , fom niigot jurn kan vara •> (a at d e t ,denna M eta l l , otorikylt ullägges at vara o f m id ig : i den

iu n -

S p a in an d th a t he u n d er sto o d it c a m e from th e W e st In d ies . H e h a d b e e n g iven th e m eta l b y U lr ic R u d e n sk o ld , th e n P re sid en t o f th e S w e d ish A c a d e m y o f S c ie n c e s , w h o h a d sp en t th e y e a r s from 17 4 0 to 17 4 4 in th e S w e d ish e m b a ssy in M a d r id an d m u st h ave b e e n a c q u a in te d w ith m a n y p e o p le in in flu e n tia l p o s it io n s in S pain . A fter rem o v in g t h e sa n d y c o n te n t h e w a s left w ith o n ly forty g ra in s o f a m e ta llic n a tu re; th e se h e fo u n d co u ld b e m e lte d r e a d ily w ith co p p er , th a t th e y w ere n ot a tta c k e d b y s u lp h u r ic or n itr ic a c id b u t d isso lv e d in a q u a reg ia , w h ile w ith th e a d d it io n o f a sm a ll a m o u n t o f a rsen ic th e m a te r ia l m e lte d ea s ily . (H is c h o ic e o f a rsen ic m u st su re ly h a v e o ccu rred to h im from th e w ork o f his m a ster , G eorg B ran d t, o n th is e le m e n t) . H is c o n c lu s io n s w ere:

“ 1 That this is a m etal hard b u t m alleable, but of the hardness of m alleable iron.2 T hat it is a precious m etal o f durability like gold and silver.3 That it is not any of the s ix old m etals; since first it is w holly and entirely a

precious m etal, containing n oth ing of copper, tin, lead, or iron because it allows nothing to be taken from it. It is not silver, nor is it gold; but it is a seventh metal am ong those w hich are known up to now in all la n d s.”

F in a lly he r e co m m en d e d t h a t :“This m etal is the most su itab le of all to m ake telescope mirrors because it resists

as well as gold the vapours of the air, it is very heavy, very dense, colourless and m uch heavier than ordinary gold, w hich is rendered unsuitable for this particular use by lacking these two latter properties. There rem ains only to be found the m anner of giving white gold unity and a proper state and a m ixture that can aid to m elt it and to m ake it capable of receiving a p olish . ”

T h e opening of Henrik Theophil S rheffer 's p a p e r read to the Royal Swedish Academ y of Sciences on Novem ber 28th. 1751. T h e title reads: " T h e W hite Gold or Seventh Metal called in Spain 'P la t in a del Pinto". Little Silver of Pinto, its Nature Described ". This records that ill Ju n e 1750 he had received a sample of native plat inum from the President of the Academy. I lric R udenskold . After removing the sandy content the sample weighed only forty grains, but Seheffer was none the less able to m ak e a thorough exam ination of the new metal

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T his was the first accu ra te ex am in a tio n of p la t inum , ca rried out o n an extremely small quan tity , bu t im m edia te ly afte rw ards, a n d also d a ted N ovem ber 28th, 1751, Scheffer re ad a short p ap e r to the A cadem y “ A n A d d e n d u m on the Same M e ta l” (10) in which he refers to an o th e r sam ple of m ater ia l th a t he h a d received from Brandt, who h ad also h ad it from R udensko ld . In this su p p le m entary com m unica t ion he reported that the m etal, unlike gold, w as not p re c ipita ted from solution in aq u a regia by ferrous su lphate , b u t tha t it was p re c ip ita ted by alkalies a n d by am m o n ia in the form of a red pow der. T h is last observation, as will be seen, was a very im p o rtan t one th a t led on to m u ch useful research.

William Lewis of LondonBefore W illiam W a ts o n ’s com m unications were pub lished by the Royal Society and therefore well before Scheffer had s tarted his work, a L ondon physic ian and lecturer h a d begun a m ajor series of experim ents w ith p la t inum . T h is was Dr. W illiam Lewis (1708-1781) of K ingston -upon-T ham es, b u t as he d id not publish his findings until 1754 Scheffer m u s t be accorded priority as the first follower of W atson in the pub lica tion field.

LXXXVI. Expérimentai Examination of a -¡¿bite metallic Subftanct [aid to be found in the Gold Mines of the Spanifh Weft- Indies, and there Inown by the Appellations of Platina, Platina di Pinto, Juan Blanca. By William Lewis, AC B. F. R . S.

P A P E R LRead May 30 , »154.

Experiment I.

T H E fnbftance brought into England tmder the name ofplatina appears a mixture of dilftmilar

particles.The moft conspicuous, and by far the largeft part

o f the mixt, are, white, fhining grains, of feemingly fmooth furfaces, irregular figures, generally planes with the edges rounded off. Upon examining thefe with a microfcope, the furface appear'd in fome parts irregular -, the prominencies fmooth, bright, and ihimng ; the cavities dark-colour'd and roughiih. A few of them were at trailed, tho’ weakly, by a magnetic bar.

The grains above deicrib'd are the true platina. The heterogeneous matters intermingled among them, in the feveral parcels, were,

i. A

Before Seheffer 's researches were known to him William Lewis had e m b a rk ed on a long series of researches on p la t inum . Vi ¡thin five weeks from late May lo early July in 1754 he read four papers to the Royal Society, with a fu r th e r two in 1757. T his is the opening page of his first p a p e r from the P hilosophica l Transactions

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Lewis was a skilled ex p e r im en te r as well as a prolific a u th o r a n d editor, and in his time he was the u n d isp u ted au tho ri ty on any subject on w hich he wrote. H e had, in fact, a considerab le influence on the chem ical technology of the Industria l Revolution. Lewis s tu d ied m edicine first at C hris t C h u rch , Oxford, a n d later at E m m anuel College, C am bridge . H e th en settled in L o n d o n and soon becam e estab lished as a p u b l ic lec tu rer on chem istry an d on the im provem en t of ph arm acy a n d the m a n u fa c tu r in g arts. In 1745 he was elected a Fellow of the Royal Society and two years la te r he moved to K ingston w here he equ ipped a large laboratory . A n excellent account of the life an d work of W illiam Lewis, until then a lm o s t a forgotten man, w as provided by the late F . W . G ibbs in 1952 (12).

Lewis was acq u a in ted w ith Brownrigg, a n d he w as p erm it ted to select a small sample from the specim ens th a t h a d been p resented to the Royal Society. O n these he m ad e a few p re lim in ary observations b u t it was not until early in 1754 tha t he ob ta ined a sufficient q u an t i ty for his extensive research. T h is he secured from General R ich a rd W all (1694—1778), a n Irish R o m a n Catholic who, unable to hold any public office because of his faith, h ad served the Spanish King Ferd inand VI in a n u m b er of posts, including one in the South A m erican colonies. In 1747 he was a p p o in te d Span ish am b assa d o r to L o n d o n a n d was elected to the Royal Society in 1753, clearly becom ing know n to Lewis a t tha t time. T h ro u g h W a ll’s influence, Lewis w as sent one h u n d re d ounces of p la t in u m from Spain, w ith a fu rther q u a n t i ty a year or tw o later.

T h e results of Lew is’s long a n d exhaustive series of experim ents were read to the Royal Society in 1754 in four long pape rs over the course of only five weeks (13). H e went abou t his work a n d reported his findings in a m a n n e r so logical, c lear an d almost m odern in c h a ra c te r th a t his pape rs p resen t the first au th o r itative and com prehensive accoun t of the p roperties of p la t inum .

In the first p ap e r Lewis s u m m e d up his conc lus ions :“ That the pure platina is a white metallic substance, in some small degree malle

able; that it is nearly as ponderous as gold, equally fix’d and permanent in the fire, equally indestructible by nitre, unaffected by sulphur. That it is not to be brought into fusion by the greatest degree of fire procurable in the ordinary furnaces, whether expos’d to its action in close vessels, or in contact with the fuel; by itself, or with the addition of inflammable, saline, vitreous or earthy fluxes. ”

T h e second p ap e r recorded th e effects of acids up o n p la t in u m freed from its con tam inating dust, m ercury a n d gold. Its insolubility in sulphuric , hydrochloric an d nitric acids w as noted, an d of course its solubility in aq u a regia, bu t his most im portan t discovery was th a t :

“The spirits of sal-ammoniac added to solutions of platina (in aqua regia) diluted with distilled water, precipitated a fine red sparkling powder; which, exsicated and expos’d to the fire in an iron ladle became blackish; without at all fulminating, which calces of gold, prepar’d in the same manner, do violently.”

P apers III an d IV described a long series of experim ents in the m elting of p la t in u m alloyed with practically every o th e r m etal th en know n an d some of

38



their alloys, b u t curiously he d id not th en try the effect of arsenic. T h e idea was th a t the best hope of bring ing p la t in u m into a m alleab le form th a t cou ld be fabricated was by alloying it with an o th e r m etal, bu t little progress resu lted from these experim ents except his finding th a t if a n alloy of lead a n d p la t in u m was thoroughly oxidised at a high tem p era tu re it yielded a spongy m ass th a t could be forged.

After the publication of Papers I to IV Lewis o b ta in ed a copy of Scheffer’s com m unica t ion to the Swedish A cadem y in w hich he found

“a remarkable experim ent seem ing to show that p latina and arsenic have some disposition to unite. ”

and he at once set abou t repea ting it in several different ways w ithou t great success. H e concluded th a t :

“ It appears upon the whole, that platina does melt w ith arsenic, but less perfectly than with other m etals; and that it w ould be very difficult, if not im possible, to bring it, on this foundation to sufficient fusion for being poured into a m ou ld .” (14)

O n m elting p la t in u m together w ith an equal p a r t of gold Lewis ob ta ined a brittle alloy a lthough it could be worked after annealing , a n d this finding d rew a letter from Brownrigg to W atson , read to the Royal Society in the following December, in which he wrote:

“ Dr. Lewis will find that Platina being m ixt w ith Gold destroys the ductility of that metal. H ow Gold is affected with a very sm all proportion of Platina I know not, but my acquaintance Mr. Charles W ood (who was A ssay M aster in Jam aica) a very curious man th o ’ he m ight be m istaken in som e things, show ed m e about a drachm weight of a substance w hich he said was Platina and Gold m ixed by him in equal quantities. This m ixture was extrem ely b rittle .” (15)

Lewis was lavish in his use of p la t in u m in his experim ents , for in m ost of them he took a t least one ounce a n d som etimes even three or four ounces as s tarting m aterials. O n e o ther aspect of his work, po in ted ou t by Professor Cyril Stanley Sm ith (16) is th a t he m ad e one of the earliest observations of the m icrostruc ture of a n alloy as a n a id to in terp re t ing its const i tu tion w hen he noted the complex s tru c tu re of incompletely m elted alloys of p la t in u m an d gold:

“ Some appeared to have suffered no alteration; others exhibited an infinite number of minute globular protruberances, as if they had just begun to melt.”

For this ou ts tand ing work Lewis was aw ard ed the Copley M eda l by the Royal Society in 1754, b u t he con tinued his experim ents , p ro m p te d by Brownrigg’s letter, on the alloying of p la t in u m with gold, in a n a t tem p t to ascertain :

“whether there is reason to credit the report of great frauds having been com m itted by m ixing them together; how far such abuses are practicable; and what is o f more importance, the m eans by w hich they are d iscoverable.”

So Papers V a n d VI, re ad to the Royal Society in M a rc h 1757, (17) dealt largely with the m ethods of assaying an d sepa ra t ion of the metals.

39



In 1763 W il l i a m L ew is p u b l i s h e d his e la ss i r " C o m m e r c i u i n P h i lo so p h ic o - T e e h n i e u m " . d e d i c a te d to G e o rg e III to w h o m he h a d g i \ e n p r i v a te tu i t io n w h e n he was P r i n c e o f W ales . T h is i n c l u d e d a long s e c t io n r u n n i n g to 170 p ages th a t fo r m e d th e first a u t h o r i t a t ive a n d c o m p r e h e n s i v e w ork on th e h is to ry a n d th e p r o p e r t i e s o f p l a t in u m . T h is w ork w as m u c h c o n s u l te d f >r th e nex t t h r e e - q u a r t e r s of a c e n t u r y , a n d e \ e n as late a s 1880 J o h n P e rc y , P r o f e s s o r of M e ta l lu rg y at the R oyal S choo l of M ines in L o n d o n , r e f e r r e d to it a s 'a v o lu m e ra re ly a p p r e c i a t e d as it o u g h t to b e . . . it c o n t a i n s m u c h i n f o r m a t io n o f sc ien t i f ic in te re s t a n d of p ra c t i c a l \ a lu e “

There was yet more to come from William Lewis. Beginning in 1763, he published a massive volume in parts, the Commercium Philosophico — Technicum A long section was devoted to the chemistry and applications of gold, and, following another part dealing with colours and pigments, there appeared a 170 page section on “The History of P la tinum ” (14). Lewis wrote in introducing this:

“Nothing now is so much wanted, as a regular history of what has already been done, or a connected view of the experiments that have been made upon it. ”and this he set out to provide. It included of course his own work as well as that of the leading chemists of Sweden, Germany and France whose work had to a large extent stemmed from his own.

W illiam B ow les and his R esearches in SpainIt was mentioned in the last chapter that in 1753 the Irish naturalist William Bowles examined a sample of native platinum from South America at the request of the Spanish Minister of the I ndies and that he issued a warning on the dangers of admitting this new m etal into commerce. His report on his experiments describes how, after separating the gold and the blackish sa n d :

40



“The grains of platina then resembled lead shot, still more the semi-metal which the Germans called speiss, which is a regulus of cobalt often included in saffre. The weight of the platina surprised me because it exceeds that of 20 carat of gold. I put several pieces of it on an anvil and hit them with the hammer. I saw they extended their diameter five or six times, remaining white as if they were silver. This determined me to send them to a gold beater to determine the extent of their malleability, but when tested between the beater’s skins they broke up at once. In remarking that the sand was only malleable to a certain extent I wished to try to melt it in a furnace which a very clever Swiss used for the separation of gold by the dry way. The fire was so violent that it melted a part of the crucible and the grains of platina united themselves in a group without any loss of colour or sign of true fusion, after two hours of the most lively fire. Seeing the grains joined together, I thought that the platina might contain some portions of true sand and that this would be vitrified by the phlogiston of the metal. To convince myself, I washed a little of the platina and put it in another crucible glazed with common melted salt. After three hours nothing had melted but the grains were not so strongly united as the first time, several even remaining separate.”

H e then found th a t the p la t ina was not a ttacked by su lphuric an d nitric acid bu t there was some attack (probably on the sands) by hydrochloric acid. T h e p la tina was dissolved after “ I th rew on the acids a s trong dose of sal- am m o n iac” . H e noted th a t the gra ins of p la t ina w hich h ad been un ited by hea t broke up u n d e r a very light h a m m er blow. H e exam ined the ac tion of su lphur, lead an d cupella tion; he noted th a t the solubility in gold w as limited a n d tha t the alloy with lead could be m elted an d cou ld be p a r te d in nitric acid, leaving an infusible black powder. (18)

No further research work on p la t in u m took p lace in Spain for a q u a r te r of a century an d an accoun t of this will be found in C h a p te r 6.

Marggraf’s Work at the Berlin Academy of SciencesSoon after his accession to the th rone of Prussia in 1740 Frederick the G reat, am ong m any o ther activities, revived the declining Royal P russian A cadem y of Sciences th a t h ad been founded in 1700 by his g ran d fa th e r Frederick I, on the persuasion of Leibniz, to em ulate the Royal Society of L o n d o n an d the F rench A cadem y of Sciences. T o this end he invited to Berlin bo th L eo n h a rd Euler, the Swiss m athem atic ian , an d la ter Pierre Louis M au p e r tu is from the F rench A cadem y of Sciences. E u ler was sent a sam ple of p la t in u m from L o n d o n in about 1754, and this he passed on to his leading assistant, A ndreas S ig ism und Marggraf, who h a d stud ied medicine at H alle a n d th en m eta llu rgy at Freiberg, an d who was given charge of the chemical labo ra to ry in the Berlin A cadem y in 1753.

M arggraf ca rr ied out a long series of experim ents reported to the A cadem y in 1757 (a lthough not published until 1759) w ri t ten in French , the official language insisted u p o n by Frederick, while they were later pub lished in G e rm an in a collection of his papers (19).

41



M arg g ra f applied m uch the sam e procedures as the o ther investigators whose work has a lready been recorded . H e aga in observed th a t a t a very high tem p era tu re p la t in u m grains s in te red together som ew hat b u t th a t they had not been m elted a n d were easily b ro k e n up u n d e r the ham m er . H e also noted the traces of m ercury am ong the na tive p la t in u m and conc luded th a t it was a residue from a n am a lg am a tio n process. He found th a t hydrochloric acid dissolved some iron from the m in e ra l an d th a t aq u a regia also dissolved the p la t in u m itself. From this so lu tion prec ip ita tes were formed by copper, iron, tin, lead, mercury , zinc an d an tim o n y , an d with regard to tha t formed by zinc M arg g ra f rem arks th a t “ to all a p p e a ra n c e s the p la t in u m h ad been p re c ip i ta te d ” upon it. T here was no p rec ip i ta te by solutions of m inera l fixed alkali (soda); while salt of ta r ta r (potassium c a rb o n a te ) gave a yellow precip ita te . H e cupelled some of this last w ith lead a n d o b ta in ed “ a rough, greyish a n d very b rittle b u t to n which was exactly like th a t o b ta in ed w hen o rd inary p la t in a was cupelled w ith le ad ” . H e repea ted the ex p e r im en t using sa l-am m oniac as the p rec ip itan t a n d obta ined a precisely s im ilar result. T h e sam e th ing h ap p en ed w hen he evaporated his p la t in u m solution in a q u a regia to dryness, ignited the residue a n d cupelled it with lead. H e n o ted th a t in all these cases the cupelled b u t to n always contained some lead. N ex t he alloyed a sim ilar b u t to n with som e pure gold an d an excess of silver an d p a r te d the alloy in n itric acid. H e found th a t in the course of this opera t ion the p la t in u m d isappeared , the final insoluble residue being only the right weight of fine gold. H e next d em o n s tra ted the presence of iron in native p la t in u m by o b ta in in g from its so lu tion a p rec ip i ta te of Prussian

Andreas Sigism und Marggraf I 7 0 9 -1782

A native of Berlin, M arggraf was appren ticed to his fa ther , the Court Apothecary, and then studied medicine at Halle and metallurgy at Freiberg. After his re tu rn to Berlin he was elected to the Academy in 1738. He was singled out as the best chemist and in 1759 he was put in charge of the chemical laboratory in the Academy, succeeding Euler as Director in 1766. He was the first to discover that the precip ita te obta ined from a p latinum solution by m eans of am m onium chloride reverted to metal on heating

42



© J1 & < M W > < K < H H 0 O « < > 0 « 0 O < - < H W > < K O O i O < >

E S S A I SC O N C E R N A N T LA N O U V E L L E E S P E C E DE C O R P S

M l N i f t A L C O N N U SOUS LE N OM DE H J T 1 N J D E L F IN T O .

p a r M. M A R G G R A F .TtsJbU dt i AlitmAmd.

L

1 1 y • déjà quelques années que l’on eft parvenu en Angleterre à la conooiliance de corps minéral métallique, auquel on a donné le

PUtina Je! Pinto. Les Auteurs Anglois qui en parlent, difènt qu'on le trouve dans les Mines cl’O r des Indes Occidentales Espagnoles. (Voyez les Tranfaffm m , Vol. 48 . p. 6 3 8 - ) Suivanr d’autres réla- rions, ce minéral doit fe trouver en forme de iàble d.ins les rivières de la Province de Q iatn , & cela en très grande quantité. O n ne (âuroit donc dire avec aucune certitude, fi c ’cil une matière réellement-minérale, ou une iimple raclure que l’eau entraîne de quelque veine en tière , & porté avec elle dans ion cours ; ou même fi ce ne pourroit point être un pur récrément métallique, d’où les F.fpa- gnols, i qui appartiennent les mines de ces contrées, auroienr tiré de manière ou d’autre ce métal parfait. U n de nos dignes Confrères O •fibre M. le Profefleur ZtVVr, dans une Lettre qu ’il lui a écrite, qu’il tient de la bouche d’un Eipagnol qui a été dans cette Province, de qui en i apporté de la Phitina , qu’on la trouve répandue fur la campagne, près du fleuve qui traverie les montagnes du Pérou auprès de Quito. Dans les commencemens il étoit fort difficile de fc p ro curer quelque échantillon de cetto matiere ; les Efpagnols n’en vou- loicnt point communiquer, à caufe que pouvant être aiiement mêlée

avec(*) Mr. Brrtrénd de Genert

Blue on adding “ alkali that had previously been calcined with b lo o d ” ( blutlauge, containing po tassium ferrocyanide). T h e results of all these experim ents entitle him to be called the first m a n to sepa ra te metallic p la t in u m from its m ineral. To say, as some of the textbooks do, th a t he was the first to p re p a re p u re p la t in u m is of course incorrect, even by the s tan d a rd s of pu r i ty th en cus tom ary , since the metal con ta ined all the o ther p la t in u m metals, as well as o ther impurities.

Researches in FranceFrance lagged beh ind the o ther E u ro p ean countries in app ly ing scientific m ethods to the study of p la tinum .

In M ay 1751 a brief reference was m ad e to the first le tter to Bose from W atson (with his nam e mis-spelt) in the Journal Oeconomiqueu n d e r the head ing :

METAL N O U V ELLEM EN T D E C O U V E R TEExtrait d ’une lettre ecrite de Londres par M . G u illau m e W abson a M . * * * * datee du 25 Janvier 1751 (20).

This seems to have aroused no interest whatsoever, while a fu r ther m ention in the same jo u rn a l in 1755, referring to the fraudu len t use of p la t in u m in the adu lte ra tion of gold an d to Scheffer’s work, drew very little m ore a t ten t ion (21).

T he beginning of the pap er read to the Koval Academy of Sciences in Berlin in1757 under the title "E xper im en ts C oncerning the New Kind of Mineral Body known under the name of P la tina del Pinto**. The official language of the Academy was French on the insistence of King Frederick the Great

43



But in J a n u a ry 1758 there a p p e a re d a long letter to the editors of th e Journal des Sçavans, the first scientific per iod ica l th a t began pu b lica t io n in 1665, on “ A N ew M eta l called P la t in a ” , from “ M . D e la la n d e de 1’ A cadém ie R oya l Des Sciences” . T h e w riter was J o s e p h J e ro m e le F ranço is de L a la n d e (1732-1807) w ho was later to become the lead in g a s tronom er in his coun try b u t w ho was also a prolific writer on m any scientific subjects. His le tter opens by referring to the researches carried out on p la t in u m in E ng land a n d G erm any , an d goes on to justify his appearance in p rin t :

“ Because nothing has been p ub lish ed in our language on the subject, except a very sm all extract in the Journal Oeconomique, I offer for your curiosity a sum m ary of these experim ents and the com p arison w hich results betw een p latinum and the m etals already know n.”

Lalande, a t the age of only n ine teen , h a d been sent to Berlin in 1751 to m ake observations on the parallax of th e m oon a n d here, du ring his stay of nearly two years, he im pressed bo th F rederick the G rea t an d Euler a n d was elected to the A cadem y. H e would have doub tless met M arg g ra f du ring this visit, b u t his letter refers only briefly to the la t te r ’s work o n p la t in u m while it gives a lengthy accoun t of the “ profound re se a rc h e s” of W illiam Lewis.

L a te r in 1758 there was p u b l ish ed in Paris a small book u n d e r the title “ L a Platine, l ’O r Blanc, ou le H u i t iè m e M e ta l ” , consisting of a short preface by the au tho r , the two letters from W il l iam W atso n to Professor Bose, a n account of the experim ents of Charles W ood a n d the com m ents of Brownrigg up o n them , Scheffer’s papers to the Royal A cad em y of Sweden, L ew is’ pap e rs of 1754, an d a som ew hat alchemical letter co m m en tin g o n all these from a n an o nym ous Ita lian living in Venice (23). In fact, th e book co n ta in ed a very good su m m ary of the work carried out on p la t in u m in o th e r countries up to a n d including 1755. It was p r in ted anonym ously bu t the a u t h o r ’s n a m e was given as M . M orin , “ a m an zealous in the process of science a n d a savant h im self” , by M acq u er , to w hom the m anuscr ip t h ad been s u b m it te d for approval in O c to b e r 1757, in his D ictionnaire de Chimie, p u b l ish ed in 1766. However, the tru e identity of this m a n rem ains som ew hat in doubt. T h e book has often been a t t r ib u ted to C laude M orin , a lawyer in Dijon, bu t he w as no scientist an d it is m u ch m ore likely to have been the work of J e a n M o r in (1705-1764), C an o n a n d Professor of Philosophy at Chartres, who was a co r resp o n d in g m em b er of the A cadém ie des Sciences from 1736 onw ards an d w h o w rote two or th ree o th e r scientific works, m ain ly on the subject of electricity.

T h is book was given a long a n d quite en thusiastic review in the J u n e issue of the Journal des Sçavans, an d the effects of these publications o n th e scientists of Paris was now im m ediate , p a r t icu la r ly u p o n M a c q u e r himself. His colleague A ntoine Baumé had ob ta ined at t h e end of the su m m er of 1757 ab o u t a p o u n d of p la t in u m presented by José A rcad io O rtega , the secretary of the Academ y of Medicine, M adrid , an d together th ey set ou t to repeat som e of the experim ents ca rr ied out by their predecessors, es tab lish ing to their satisfaction th a t this new

44



T he title page of the small book published anonymously in Paris in1758 and including F renc h translations of all the contributions so far m ade on platinum, with “ reflections on the nature and on the essence of this s ingular substance". T he au th o r was given as Morin b\ M acquer. who had been r e q u i r e d to a p p ro v e the manuscript prior to publication, and was most probably Je a n Morin, a priest and scientist of Chartres who was a c o r r e s p o n d i n g m e m b e r o f the Academic des Sciences. This little book. together with the paper published by Lalande a few months earlier, at last prom pted the scientists of Paris to take an interest in p latinum

L A PLATINE,L’O R B L A N C ,

o uLE HUITIEME METAL;

R E C U E I L ¿’Expériences faites dans les Académies R oyales de Londres, de S uede, &c. fur une nouvelle Subftance m étallique tirée des M ines du P éro u , qui a le poidsSi la fixité de l’Or.

Ouvrage intèrejfant pour Us Amateurs de l'H if- toire naturelle, de la Phyjîque & de la Chymie,

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Iftile dans Us A r ts , qui peuvent employer cette Sul/lance à fabriquer des Miroirs qui ne Je lernijptnt point à l 'A ir , (/ à iu r au Cuivre fa facilité à contracter U Vcri-dc-gris.

A P A R I S ,L E B R E T O N , Imprimeur ordinairef L E B R E T O N , Imprimeur

\ du R O I , rue de la Harpe. J D U R A N D , rue du Foin.

; ' o r o c r\ t1 «..■>: j . r « « »

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Françoile.

M. D C C . L V I I I .Avec Approbation & PtrmiJJion du R oi

body was indeed a new element. (M a rg g ra f ’s p ap e r h ad not yet ap peared in prin t at this time). T he ir p ap e r was read to the A cadém ie in N ovem ber 1758 and published in the M em oirs for th a t year a lthough these were not p r in ted until 1763 (24).

T he p ap e r opens with a n expression of“ a kind of tem erity in publishing at present a work carried out in a very short space of tim e and in w hich one has only repeated a part of the researches of M . L ew is”,

b u t also makes the im p o rtan t point realised by the scientists of the tim e :“As it is im possible to exam ine the essential properties of a m etal, that is to say

45



Pierre Joseph Ylacquer 1718-1784

Although beginning his career as a physician M arquer was especially interested in chemistry and in 1745 he was elected to the Académie des Sciences. He began to publish papers from then on and in 1757. in collaboration with Antoine Baumé. started cou rses on c hem is try in their laboratory. In the following year they undertook a study of p latinum but a lthough they were unsuccessful in a ttem pts to bring about its fusion they satisfied themselves that it was a distinct metal. Macquer later became I’rofessor of Chemistry at the Ja rd in du Koi and the leading French authority on the subject

those from which one can judge th e usefulness that one m ight expect from it, such as its ductility and hardness, w ithout m elting it alone to obtain an ingot of a certain size, we have first thought it necessary to ascertain w hether there is any hope of m elting this metal. ”

At this time M acquer , a p a r t f ro m his lecturing on chem istry , h a d ju s t been ap po in ted assistant to J e a n Hellot, the scientific d irec to r of the porce la in factory at Sevres, a n d after an abortive a t te m p t , lasting fifteen hours, to melt p la t in u m in a wood fire, he exposed a small q u a n t i ty in a crucible in the porce la in furnace, “ the greatest degree of fire k n o w n ” . After five days a n d n ights no change was discernible in the p la tinum , b u t th e crucible h ad collapsed.

After several m ore unsuccessful a t tem p ts M ac q u e r a n d B aum e decided to de term ine w hether p la t in u m was essentially infusible o r not by exposing it to the hea t from a large concave b u rn in g mirror, a device th en th o u g h t to be more powerful th an any kind of fire. W i th this m irror, m ad e of m ercury-coated glass a n d 22 inches in d iam eter, they qu ick ly m elted iron a n d several m ineral substances. T hen , on O c tobe r 16th, 1758, “ the su n being perfectly c lear an d the air very c lea n ” , they p laced at the focal length of the m irro r a small piece of p la t in u m tha t h ad a lready been th ro u g h the porcela in furnace a n d th a t was sufficiently agglom erated to be held in a pair of pincers. T h ey were at least partia lly

46



successful this time, in th a t glistening ro u n d ed partic les of a silvery-white metal began to a p p e a r at a few points in the small m ass of m ater ia l. S ep ara t in g the largest of these from the unm elted residue with their fingers, they found th e m to be readily m alleable a n d were able to h a m m er th em to foil w ithou t any signs of cracking. But M a c q u e r ’s hopes of p roduc ing even a small ingot of p la t in u m with which to determ ine its properties were not fulfilled.

T hey confirm ed the solubility of p la t in u m in a q u a regia a n d its p rec ip ita tion by sal-am m oniac , a n d a t tem p ted to melt the precip ita te u n d e r a flux an d found th a t the result, which at first sight looked like fusion, was really no th ing more th an an agg lu tina tion of the partic les, the p roduc t being q u ite brittle . In the course of precip ita tions of the p la t in u m with vegetable fixed alkali (p o tash ) and volatile alkali (am m onia ) they found tha t the colour of the precip ita tes varied from one occasion to ano ther , from brigh t red th rough all shades of o ran g e to pure yellow. M a c q u e r tho u g h t th a t this depended on the s treng th of the solution, while B aum e a t t r ib u ted it to the excess or o therw ise of precip itan t. Lewis h ad com m ented on these conclusions bu t he did not p u rsu e the m atte r , a n d the answ er cam e only with the discovery of ir id ium nearly half a cen tu ry later. A full

Antoine Baume1728-1804

A m aster apo thecary . Baume opened a pharm acy in Paris in 1753 and m an u fac tu red drugs on a considerable scale. In 1757 he co-opera ted with M acquer in conducting courses in both chemistry a n d pharm acy which continued for sixteen years. Baume equ ipp ing the laboratory and p repar ing the experiments , l i e first suggested that p la t inum could be consolidated by heating and forging

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account of all this work will also b e found in M acque r’s Dictionnaire de Chimie (25) but a very important deduction from it did not see the light of day until Baumé published his three volume textbook Chymie Expérimentale et Raisonée in 1773 (26). Here he says of p latinum :

“ It combines in its admirable properties a quality still more precious which is lacking in gold, hardness. This approaches very nearly that of iron. So many excellent properties united in a single metal make it desirable that it should be introduced into commerce. There is every reason to believe that it will be possible to derive very great benefits from its use in an infinity of utensils, which made out of this metal will not be susceptible to attack by any kind of rust. For example, I have noticed that it submits to forging and welding like iron, without the introduction of any other metal. I have taken two pieces of platinum which have been cupelled in a Sèvres furnace; I have raised them to a white heat in a good forge: having placed them one on the other, and struck them with a sharp hammer blow, they have welded together just as well and solidly as two pieces of iron would have done. This property of platinum of being malleable when hot and being capable of welding in that state, leads one to hope for the greatest advantages by treating it in this way when one cannot reach finality by fusion. The case of platinum would then be the same as that of iron, with which all kinds of work can be done without our being obliged to melt it. It will be sufficient to melt this new metal a single time, either alone, or by means of lead or bismuth, and subsequently to destroy these metals in the manner we have described above.”

This observation of B aum é’s a n d the conclusion that he drew from it were responsible for the start of the fabrication of p latinum for commercial uses and underlie the industry that gradually grew up during the next hundred years. The right of priority in this discovery was accorded to Baumé by his contemporaries without any hesitation and a typical example of the credit will be found in Professor Joseph Black’s “ L ecture on Platina, or P la tinum ” delivered to his students in the University of E d inburgh during the 1780s. (27)

“This method of compacting platinum and uniting the parts of it by percussion, when strongly heated, was first suggested by Mr. Baumé; and it must be employed in every case in which this metal is refined. We cannot unite the parts of it by fusion with any heat that furnaces can give.”

T h e Iron-G old T h eo ryAlthough M acquer and Baumé, as well as their predecessors Brownrigg, Scheffer and Lewis, were fully satisfied tha t p latinum was an individual metal, a contrary view suddenly became apparent in France. In Ju ly 1773, at the invitation of de Morveau, the great naturalist G eorge le Clerc, C om te de Buffon, m ade a visit to the Dijon Académie des Sciences, founded in 1740, to read a memoir on platinum taken from his first supplem ent volume to the Histoire Naturelle in which he included the findings of both de Milly and de Morveau to their great gratification (28).In the course of th is he m aintained :

“ It is improper that chemists have regarded it as a new metal, perfect, individual and different from all the others . . . it is not believable that one may include in the

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The Comte de Buffon

1 7 0 7 - 1 78 HT h e f a m o u s n a tu ra l i s t G e o rg e L ouis le C le re . C o m te d e B u f f o n . a u t h o r of th e f o r ty - fo u r v o lu m e " H i s t o i r e N a tu r e l le ” a n d S u p e r i n t e n d a n t of the J a r d i n d u Roi f ro m 1739 as well as t r e a s u r e r of th e A c a d é m ie de s Sc iences . c la im e d in 1773 th a t p l a t in u m w as not a n i n d iv id u a l m e ta l b u t m ere ly a n a tu r a l a l loy o f i ro n a n d go ld . I l is g re a t r e p u t a t io n p e r s u a d e d the C o m te d e Mill y a n d G u y to n d e M o rv e a u to s u p p o r t th is v i e » bu t on ly lo r a sh o r t l im e

class of metals a substance that is neither ductile nor fusible . . . It is not at all a new metal but a mixture, an alloy of iron and gold formed by nature. ”He went on to quote the work of the Comte de Milly, who had extracted

some iron from native platinum and who also maintained that it was a natural alloy of iron and gold. Buffon further asserted that those who sold platinum were guilty of roguery.

Now' Buffon, the Intendant of the Jard in du Roi, was most highly regarded for his researches in many subjects and for his massive “ Histoire Naturelle” that eventually ran to forty-four volumes, and his views naturally carried a great deal of weight, although he was apt to indulge in rather hasty generalisations. During his visit to Dijon he presented a small quantity of native platinum to Guyton de Morveau and urged him to continue experiments and to seek a method of melting it, pointing out that a magnet would separate it into two parts, one containing iron and the other gold. Guyton confirmed these observations and at first supported Buffon’s view. In the following July there appeared a letter from Professor Blondeau of the Naval Academy at Brest, (29) questioning both Buffon’s conclusions and de Milly’s reason for supporting them. Both Guyton and Milly began to have reservations, and the iron-gold theory was finally disposed of by Bergman in 1777.

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T o r b e r n O lof B e rg m an1 7 3 5 - 1 7 8 4

P ro f e s s o r o f C h e m is t ry in (he I Diversity o f I p p s a l a f ro m 1767 un t i l h is d e a t h . B e rg m a n d e v e lo p e d m e th o d s o f q u a n t i t a t i v e a n a ly s is a n d w ro te a t r e a t i s e on ch e m ic a l aff in i t ies . In 1777 he p r e s e n te d a p a p e r o n p l a t i n u m lo t h e Sw ed ish A cad e m y of Sciences , b e g in n in g by say ing th a t " w e still lack p re c i se in f o rm a t io n a b o u t m a n y of its longes t k n o w n p r o p e r t i e s " , b u t he d i sp o s e d o n c e a n d fo r a ll of B u f fo n 's view tha t p l a t i n u m w as not an indiv ¡dual m e ta l

F ro m a p o r tr a it p a in te d by L o ren s P aso h ih e \ o u n g e r in 1778 in th e p o ssess io n o f ih e I im ersitN o f I p p sa la

T h e W ork o f Bergm anThe work of Torbern Olof Bergman (1735-1784) took place considerably later than the work already recorded in this chapter, but is related to this earlier work in that it provides a summing up and clarification of what went before. As we travel on in the study of the history of platinum it will be found tha t on several occasions, after a certain am ount of sporadic work has been carried out, there has come along a major scientific mind which has taken up the scattered results and co-ordinated and completed them : Bergman was the first of these; he was followed in the eighteen-thirties by Berzelius, curiously enough another Swede, in the eighteen-fifties by the F renchm en Deville and Debray; so Bergman, although he did not publish until la ter definitely belongs to this chapter.

In 1777 he presented a p aper to the Swedish Academy. This was subsequently printed in Latin in 1779 in Bergman’s collected “ O puscu la” , in French in 1780, and in English in 1784 (30). Bergman had obtained a quantity of platinum through his friend C laude Alstromer the botanist, who had spent some time in Spain on the suggestion of Linnaeus and who was the son of the founder of the Swedish Academy of Sciences.

There had been some doubt among the ealier investigators as to whether mineral fixed alkali (soda) precipitated p latinum from its solution in aqua regia or not. Bergman showed that while potash and ammonia, even in small quantities, gave a precipitate w ith the acid solution, soda gave it only when present in large quantities th rough neutralisation of all the free acid present or by direct addition. He noted that lime also precipitated platinum from its solution but did not realise that this reaction requires the influence of daylight and

50



takes place only very slowly, if at all, in the dark. He examined the precipitate produced by sal-ammoniac in a platinum solution and thought it to be a triple salt containing the constituents of sal-ammoniac as well as platinum, an observation which is quite correct. He noted that the crystalline precipitates obtained by adding to the acid solution small quantities of potassium or ammonium carbonates were red if the solution was strong and yellow if it was very dilute, an observation that remained unexplained for twenty-five years until iridium had been discovered. He also experimented on the melting of platinum and found that the sal-ammoniac precipitate appeared to be more easily melted than the native metal.

Platinum a Distinct M etalThe concluding part of Bergman’s paper dealt with the question of whether platinum was in fact a distinct metal. Here he declared against Buffon’s ideas and demolished his argument once and for all by both experiment and deduction:

“Since platina surpasses all metals except gold in weight, and is always found to be contaminated by iron, some scientists have believed that it could not be freed from this, that platina is nothing but a mixture of gold and iron. However, Dr. Lewis has, for several reasons, rejected this opinion. By melting together gold and iron, in whatever proportion, no such alloy is obtained which in specific gravity or other properties resembles platina in the least. Furthermore the amount of iron in the natural platina can be so reduced that it becomes hardly detectable. We do not know of any native metals that are found entirely pure. . . . When we add to this the fact that the last traces of a foreign contaminant are infinitely difficult to remove, because they are the smallest part making up the whole mass, so it is not strange if iron adheres to platina in this most obstinate manner, and rather that the difficulty in melting of platina has up to now put a special obstacle to their separation. ”

In a final paragraph Bergman expressed his view that it was a great pity that more platinum was not available in Europe so that it could be melted in some quantity, and that in the supplies of metal that do arrive there are many impurities that must be sought for with great attention to separate them all.

Bergman’s work on classification and nomenclature is well known. He continued to make use of many of the old alchemical symbols and added new ones, including one for platinum, as illustrated here, combining the old symbols for

B e rg m a n c o n t in u e d In use a l c h e m i c a l s y m b o ls for th e e l e m e n t s a n d he d o i s e d o n e fo r t h e new m e ta l p l a t i n u m , b a s e d u p o n a c o m b in a t io n of those fo r go ld a n d s i lve r . H e a lso p r o p o s e d the n a m e p l a t i n u m in s te a d o f th e w o rd p l a t i n a used u p to t h a t t im e

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gold and silver. He also proposed the use of the nam e “ p la t inum ” instead of the older “ p la tina” in line with a num ber of other metals for which he had adopted the Latin ending “ urn” .

C onclusionFrom among the results of all th is admirable work conducted in five countries, most of it in quite a short period of years, several facts emerged that were to prove of great importance in paving the way towards the ultimate fabrication of p latinum into sheet and wire. These were :

(1 )T h a t platinum, as M acquer put it, was a particular metal as fixed, indestructible and unalterable as gold and silver, different from all other known metals.

(2) Lewis’ discovery of the precipitation of p latinum from solution by sal- ammoniac, which effected its separation from iron and gold.

(3) Scheffer’s observation that the addition of a small am ount of arsenic to a much larger quantity of p la tinum brought about the complete fusion of the latter at a comparatively low temperature.

(4) The discovery by M arggraf that the precipitate obtained from a p latinum solution by means of am m onium chloride when heated reverted to metal. Also that the metal was th row n out of solution by metallic zinc.

(5) The observation by several people, but more especially studied by M acquer and Baumé, that the grains of native p latinum and the sponge produced by the ignition of the am m onium chloride precipitate, agglutinated or sintered together when exposed to the highest possible temperature.

(6) The discovery, first by M acquer and Baumé and afterwards by Bergman, that platinum could be subm itted to at least partial fusion and was then non-magnetic and malleable.

(7) The suggestion by Baumé that p latinum might be consolidated by heat and percussion.

As will be seen from later chapters, all the essentials necessary for the advances towards fabrication were present in these seven points.

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References for Chapter 3

1 D. M cD ona ld , Platinum M eta ls Rev., 1965, 9, 20—252 M r. R o b e r t Barker , p r ivate com m unica t ion , A u g u s t 19813 W. W atson , Phil. Trans., 1749-50, 46, 584—596 (T h e p a g in a t io n of these c o n t r ib u

tions is grea tly in error)4 L. B. H un t , Platinum M eta ls Rev., 1962, 6, 28-305 J . Russell-W ood. Platinum M etals Rev., 1961, 5. 66 -69 ; Ann. Science, 1950, 7,

199-2026 W. W atson . T w o letters to Bose, Physikalische Belustigungen, 1751, (1), 107—108;

(4), 285-2877 A. F. Fourcroy , S ystèm e des C o n n a issa n ce s C h im iq u e s , Paris, 1800, 6, 402-4038 L. B. H un t, Platinum M eta ls Rev., 1980, 24, 31 -399 H. T. Scheffer, K ungl. Vetensk.Akad. H andl., 1752, 13, 269-275

10 H. T. Scheffer, ibid., 1752, 13, 276-27811 A. F. C rons ted t , “ Aminnelse-tal öfver Framledne Directeuren Och Kongl, Vetensk. Acad.

Ledamot, Valborne Herr H enne Theoph. Scheffer”, S tockholm , 176012 F. W. Gibbs, A nn. Science, 1952, 8. 122—151; Platinum M eta ls Rev., 1963, 7, 66 -6913 W. Lewis, Phil. Trans., 1755, 48, 638-68914 W. Lewis, C o m m erc iu m P h ilosoph ico-T echn icum , L ondon , 176315 W. Brownrigg, Let te r to W. W atson , Royal Society Archives 1754, II, 54716 C. S. Sm ith , in Powder M etal lu rgy , ed. J . Wolff, Cleveland, 1942, 6617 W. Lewis, P hil Trans., 1757, 50, 148-16618 W. Bowles, D ise rtac ión sobre la p la t ina , In tro d u c c ió n a la H is to r ia N a tu ra l y de la

G eografía física de E spaña , M a d r id , 1775, 155—16719 A. S. M arggraf , Nouvelle M em . Acad. Roy. Sei., Berlin, 1757, 31 -60 ; C hem ische

Schrifter, Berlin, 1768, 1, 1 —4220 J . Oeconomique, 1751, M ay, 93-9421 J . Oeconomique, 1755, Ju ly , 148-14922 D elalande, J . des Sçavans, 1758, J a n u a r y , 46—5923 M orin , La Platine, l ’O r Blanc ou le H u it iè m e M eta l , Paris, 175824 P. J. M acque r , M em . Acad. Roy. Sei. Pans, 1758, 119-13325 P. J. M acque r , D ic t ionnaire de Chim ie, Paris, 1766, 2, 248-26326 A. Baume, C hym ie E xpér im en ta le et R aisonnée, Paris, 1773, 3, 19327 J . Black, P la t in u m or P la tina , L ec tu res on the E le m en ts o f C h e m is t ry , ed. J .

Robison, P h ilade lph ia , 1806, 3, 388-39528 G. L. Buffon. Obsns. Physique ( Rozier), 1774, 3, 324-328; H isto ire N atu re lle , Paris,

1774, Suppl. L 301-33929 L. Blondeau, Obsns. Physique (R ozier), M IA . 4, 15430 T . O. B ergm an, Kungl. Vetensk. A kad. Handl., 1777, 38, 317-328; Opuse. Phys. C hem ,

1779, 2, 166-183 (in L a t in ) ; Obs. sur la I^hysique, 1780, XV. 38—45; Physical and C hem ical Essays, trans. E d m u n d Cullen , L ondon , 1784, 166-183

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Louis Bernard Guvlon de Morveau

1737-1816

Horn in D ijon , (h e n (he c a p i ( a l o f t h e P r o v in c e o f B u r g u n d y . G u y to n firs( e n te re d the legal p r o f e s s i o n a n d th e n b e c a m e a m e m b e r o f (lie D ijon p a r l i a m e n t , a d d i n g t o his n a m e “ d e M o r v e a u ” f ro m a fa m i ly e s ta te . H e l a t e r t u r n e d to c h e m i s t r y a n d is ch ie f ly r e m e m b e r e d f o r his c o l la b o ra t io n with L a v o is i e r in m o d e r n i s in g c h e m ic a l n o m e n c l a t u r e bu t his w o rk on p l a t i n u m , c o n t i n u e d o v e r m a n y y e a r s , w as o f m a j o r im p o r t a n c e in e s t a b l i sh in g i t s p r o p e r t i e s a n d m e t h o d s f o r its f a b r i c a t i o n



early scientific enquiries into the properties and nature ... · in mind that casanova did not...

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