78. Platinum - Elementymology & Elements Multidict

Elementymology & Elements Multidict

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Platina, Witgoud† – Platin – Platine – Platino – 白金 – Платина – 鉑
Multilingual dictionary

Platinum Latin

— Germanic
Platinum, Witgoud † Afrikaans
Platin Danish
Platin German
Platinum English
Platin Faroese
Platina Frisian (West)
Platína Icelandic
Platin Luxembourgish
Platina, Witgoud† Dutch
Platina Norwegian
Platina Swedish

— Italic
Platin Aragonese
Platinã Aromanian
Platín Asturian
Platí Catalan
Platino Spanish
Platine French
Platin Friulian
Platino Galician
Platino Italian
Plàtin Lombard
Platin Occitan
Platina Portuguese
Platină Romanian - Moldovan

— Slavic
Платина [Platina] Bulgarian
Platina, ²Platinum Bosnian
Плаціна [placina] Belarusian
Platina Czech
Platina Croatian
Platina Kashubian
Платина [Platina] Macedonian
Platyna Polish
Платина [Platina] Russian
Platina Slovak
Platina Slovenian
Платина [Platina] Serbian
Платина [platyna] Ukrainian

— Baltic
Platina Lithuanian
Platīns Latvian
Platėna Samogitian

— Celtic
Platin Breton
Platinwm Welsh
Platanam Gaelic (Irish)
Platanam Gaelic (Scottish)
Platinum Gaelic (Manx)
Platynum Cornish

— Other Indo-European
Λευκοχρυσος [lefkochrysos] Greek
Պլատին [platin] Armenian
Platin[i] Albanian

— Indo-Iranian/Iranian
Platîn Kurdish
Платина [platina] Ossetian
Платина [Platina] Tajik

— Indo-Iranian/Indo-Aryan
প্লাটিনাম [plāṭināma] Bengali
پلاتین [platyn] Persian
પ્લૅટિનમનો [pleṭinamano] Gujarati
प्लाटिनम [plāṭinama] Hindi

Plaatina Estonian
Platina Finnish
Platina Hungarian
Платина [Platina] Komi
Платина [Platina] Mari
Сияжа [sijazha] Moksha
Plaatina Võro

Platin Azerbaijani
Платина [Platina] Chuvash
Платина [platina] Kazakh
Платина [Platina] Kyrgyz
Цагаан алт [cagaan alt] Mongolian
Platin Turkish
ئاق ئالتۇن ['aq 'altun] Uyghur
Platina Uzbek

Other (Europe)
Platinoa Basque
პლატინა [platina] Georgian

بلاتين [blātīn] Arabic
פלטינה [platina] Hebrew
Platinu[m] Maltese

Pha̍k (鉑) Hakka
白金 [hakkin] Japanese
백금 [paeggeum] Korean
แพลทินัม [plaethinam] Thai
Platin Vietnamese
[bo2 / bok9] Chinese

Platino Cebuano
Platina Indonesian
Platinum Māori
Platinum Malay

Other Asiatic
പ്ലാറ്റിനം [plāṟṟinam] Malayalam
பளாட்டினம் [paļāţţiṉam] Tamil

Palata Lingala
Platinamo Sesotho
Platini Swahili

Platino Nahuatl

Qullqiya Quechua

Platina Sranan Tongo

Plateno Esperanto

New names
Platinon Atomic Elements
Beatims Dorseyville
memory peg

Very bright, dense white metal
melting point 1772 °C; 3222 °F
boiling point 3827 °C; 6921 °F
density 21.45 g/cc; 1339.08 pounds/cubic foot
(Described by Julius Caesar Scaliger (1557), and Antonio de Ulloa y Garcia de La Torre (1748)
1750 sir Charles Wood (& William Brownrigg and sir William Watson), England
platina (del Pinto) = small silver (beads) of the river Pinto (Spanish)

History & Etymology

Impure, native platinum seems to have been used unwittingly by ancient Egyptian craftsmen in place of silver, and was certainly used to make small items of jewellery by the Indians of Ecuador before the Spanish conquest. To the South American Indians Platinum was available only in the form of fine, hand-separated grains which must have been fabricated by ingenious, if crude, powder metallurgy. Despite being worked with some skill by those Indians over 1,000 years ago, it was not until after the Spanish conquest of the New World during the fifteenth and sixteenth centuries that news reached Europe of a new white metal with unusual properties.

The first European reference to Platinum appears in 1557 in the writings of the Italian humanist Julius Caesar Scaliger (1484-1558) as a description of a metal impossible to melt found in Central American mines between Darién and Mexico (note):

Præterea scitio, in Fundaribus, qui tractus est inter Mexicum, & Dariem, fodinas esse orichalci: quòd nullo igni, nullis Hispanicis artibus hactenus liquescere potuit. Adhæc non omnibus metallis uerbum, liquescere, uidemus conuenire.
("Furthermore, in the foundries, it is known [scitio leg. scito] that there are deposits of a metal, which is mined between Mexico and Dariem [=Panama], that hitherto cannot be melted by any fire nor by any Spanish techniques. So far [adhaec leg. adhuc?], we see no report that it melts to alloy with all metals.").

By the end of the 17th century, the Spanish conquistadors invaded the Chocó region (now Colombia). They started developing the riversoil looking for gold and to their big surprise they found some gray looking beads together with the gold. They called those little silver beads "Platina" meaning small silver (diminutive of plata = silver). They became known as platina del Pinto, that is, granules of silvery material from the Pinto River, a tributary of the San Juan River in the Chocó region of Colombia.

The Spanish astronomer and naval officer don Antonio de Ulloa y Garcia de La Torre (1716-1795) was in 1735 with don Jorge Juan y Santacilia (1713-1773) appointed by King Philip V as members of a scientific expedition which the French Académie des Sciences was sending to Peru to measure a degree of the meridian at the equator. They remained there for nearly ten years. Among other things, he observed the Platina del Pinto, the unworkable metal found with Gold in New Granada (now Colombia). This metal was so difficult to separate from Gold that the labour wasn't worth it. When goldminers found those little silverlike beads they just tossed them away. The native inhabitants believed that if they give these beads back to the river,the river would take care of them for a further ripening proces and after a while they should return as little gold beads.

In 1745, having finished their scientific labours, Juan and De Ulloa returned to Spain on different ships, to cover the loss of their papers. De Ulloa's frigate Déliverance was attacked by privateers and finally captured by the British navy. He was brought to London and his papers confiscated, but was fortunately befriended by members of the Royal Society and was made a Fellow of that Society in 1746 when his papers were returned. With Juan, he published in 1748 the Relación histórica del viage a la América Meridional the account of his expedition in which he refers to platinum. (note).

In 1741, the British metallurgical scientist Sir Charles Wood got some grains of "Platina" on Jamaica and brought those to England in 1741 in the hope to find a commercial application for this metal. They were researched and described by William Brownrigg (1712-1800), physician, chemist and country gentleman of the town of Whitehaven in Cumberland, in a letter to the English physicist Sir William Watson (1715-1787), who also received some of these grains. Watson read Brownrigg's account for the Royal Society of London on 13 December 1750. Here Platinum was first described as a new metal (note). The full text of this contribution from the Philosophical Transactions is at the bottom of this page.
Wood and Brownrigg did not know about De Ulloa's work, but Watson knew and he translated it at the end of his paper. It became known as "white gold" (a term now used to describe an Gold/Palladium alloy) and the "eighth metal" (the seven metals Gold, Silver, Mercury, Copper, Iron, Tin, and Lead having been known since ancient times).
In 1763 William Lewis described the grains of the Royal Society as easy meltable alloys (note). Also Carl Graf von Sickingen described them as an alloy of Copper, Tin, and Platinum (note).

William Hyde Wollaston and Smithson Tennant, who had befriended at Cambridge, formed in 1800 a secret partnership to share expenses and income from ventures in commercially production of platinum. They knew that malleable platinum, if it could be produced, could replace gold in a number of applications where an inert, noble metal was required. They worked for over 15 years in the treatment of South American ores. First they intended to market small Platinum implements such as crucibles and evaporating pans, but later large markets opened up in the gunnery business and sulphuric acid manufacture (platinum boilers). Sales of platinum up to the 1820s amounted to about £30,000, some shared with Tennant until his death in 1815, but most going to Wollaston himself (Usselman, 2001).
The process to purify platinum was developed by Wollaston. The crude platinum ore was selectively dissolved into aqua regia (a mixture of nitric and hydrochloric acids), precipitated by sal ammoniac (ammonium chloride), and heated to give residual platinum powder. The resulting solution was initially thrown away. However, Wollaston studied this solution leading to the discovery of Palladium (1802), and of Rhodium (1804). Tennant examined the insoluble residue and found Osmium (1803) and Iridium (1803). Forty years later Ruthenium was found in this waste.

Watson (after Wood and Brownrigg) and De Ulloa named the metal with the Spanish name "platina del pinto", or shorter just "platina". By this name it was obviously known in South America. A variant name mentioned by Wood is "Juan blanco". Henrik Theophilus Scheffer (1752) named the new metal "white gold" since it was very much like gold, or the "seventh metal" (note). This name is still in use in jewelry, and is the official name of the metal in Greek. Claude Morin, however, considered it as the eighth metal, counting mercury as a metal instead of a semi-metal as his colleagues did (note).

Translated names

The Greek name means "white gold", just as the former Dutch name witgoud (still in use for jewelry) and the Japanese name (the two Chinese characters are 白 haku, byaku = white and 金 kin, kon = gold).

Post Scriptum

Many websites with periodical systems write that Scaliger discovered Platinum in 1735 (or even 1750) in Italy! Others give "De Ulloa 1735" as date and name of discovery, which is incorrect too. The year has to be 1748.
When the first European description is considered as the "discovery", it should be "Scaliger 1557", the first description as a new metal would be "Brownrigg 1750".

Chemistianity 1873
PLATINUM, the Chemists' pot metal,
In colour is bright white, and never tarnishes
In any case in pure dry, or moist, Air;
'Twill not oxide or fuse in a blacksmith's fire,
And melts only by heat of Compound Blowpipe flame
Or Electricity. At high temperature
It will weld like Iron, and may then be compacted.
Whether hot or cold 'tis very mall'able.
J. Carrington Sellars, Chemistianity, 1873, p. 183
Further reading
  • Platinum. Gmelins Handbuch der anorganische Chemie, 8. Aufl.; System-Nummer 68 (1951).
  • Gold and Siver Mines.com, "More About Platinum" (on-line).
  • Hunt, L.B. Platinum Metals Rev. 24,31 9 (1980)
  • Petrus, Tracy, "Platinum - Nature's Most Precious Metal". 2001 at http://www.talkwithtracy.com/platinum.htm (now gone).
  • Robertson Research Int'l Ltd., Dr. Rob's Chem4all, Quote of the week
  • Usselman, Melvyn, "A secret history of platinum". Chembytes e-zine, December 2001 (on-line).
  • Weeks, Mary Elvira, Discovery of the Elements, comp. rev. by Henry M. Leicester (Easton, Pa.: Journal of Chemical Education, 1968), pp. 385-407.
  • McDonald, Donald, A History of Platinum. Johnson Matthey & Co Ltd., 1960. (not seen).
XII. Several Papers concerning a new Semi-Metal, called Platina; communicated to the Royal Society by Mr. Wm. Watson F.R.S.

Philosophical Transactions 46 (1749/50), pp. 584-596.

Authorship is complicated: William Watson reads on 13 December 1750 to the Royal Society a letter (I) and a memoir (II) from William Brownrigg; in the memoir (II) Brownrigg describes experiments done by Charles Wood, which were repeated by himself. Watson adds himself a extract from the book by Antonio de Ulloa (III). On 20 December a short note was added by Emanuel Mendes da Costa (IV) and finally, on 28 February 1751 Watson reads a second letter of Brownrigg (V). [p. 584]

I. Extract of a Letter from William Brownrigg M.D. F.R.S. to Wm. Watson F.R.S.

Read Dec. 13. 1750.
Whitehaven, Dec. 5, 1750

Dear Sir,
I take the Freedom to enclose to you an Account of a Semi-metal call'd Platina di Pinto; which, so far as I know, hath not been taken notice of by any Writer on Minerals. Mr. Hill (note), who is one of the most modern, makes no mention of it. Presuming therefore that the Subject is new, I request the Favour of you to lay this Account before the Royal Society, to be by them read and published, if they think it deserving those Honours. I should sooner have published this Account, but waited, in hopes of finding Leisure to make further Experiments on this Body with sulphureous and other Cements; also with Mercury, and several corrosive Menstrua. But these Experiments I shall now defer, until I learn how the above is receiv'd. The Experiments which I have related were several of them made by a Friend (note), whose Exactness [p. 585] in performing them, and Veracity in relating them, I can rely on: However, for greater Certainty, I shall myself repeat them. I am, dear Sir,
Your most obedient Servant,
W. Brownrigg.

II. Memoirs of a Semi-metal called Platina di Pinto, found in the Spanish West Indies.

Altho' the History of Minerals, and other fossil Substances, hath been diligently cultivated, especially by the Moderns; yet it must be acknowleged, that, among the vast Variety of Bodies which are the Objects of that Science, there still remains Room for new Inquiries.
No Wonder that, among the great, and almost inexhaustible Varieties of Salts, Ores, and other Corncretes, new Appearances and Mixtures before unknown, should daily be discover'd: But that, among Bodies of a more simple Nature, and particularly among the metalline Tribe, several distinct Species should still remain almost wholly unknown to Naturalists, will doubtless appear more strange and extraordinary.
Gold is usually esteem'd the most ponderous of Bodies; and yet I have seen, in the Possession of the late Professor s'Gravesande (note), a metalline Substance, brought from the East Indies, that was specifically heavier than Gold, by at least a twentieth Part. Mercury, next to Gold, is commonly said to be the heaviest Body; yet Mercury is greatly exceeded in specific Gravity [p. 586] by a Semi metal brought from the West Indies, whereof I have now the Honour to present Specimens to the Royal Society. And this Semi-metal seems more particularly to deserve our Attention, as it is endu'd with some very singular Qualities, which plainly demonstrate that certain general Theorems, tho' long establish'd, and universally receiv'd by the Metallurgists, yet do not hold true in all Cases, and ought not to be admitted into their Arts, without proper Limitations and Restrictions. For instance, that Gold and Silver may be purified from all heterogenous Substances by Coppellation, is a Proposition that all Assayers and Refiners have long thought true and undeniable; yet this Proposition ought not to be receiv'd by those Artificers, without an Exception to the Semi-metal here treated of; since, like those nobler Metals, it resists the Power of Fire, and the destructive Force of Lead in that Operation.
This Semi-metal was first presented to me about nine Years ago, by Mr. Charles Wood, a skillful and inquisitive Metallurgist, who met with it in Jamaica, whither it had been brought from Carthagena in New Spain. And the same Gentleman hath since gratified my Curiosity, by making further Inquiries concerning this Body. It is found in considerable Quantities in the Spanish West Indies (in what Part I could not learn) and is there known by the Name of Platina di Pinto. The Spaniards probably call it Platina, from the Resemblance 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; it is extremely hard and compact, but, like Bath-metal, or cast Iron, brittle, and cannot be extended under the Hammer.
[p. 587] The Spaniards do not dig it in the Form of Ore, but find it in Dust, or small Grains, as herewith presented to the Royal Society. Whether they gather it in a pretty pure State, as brought to us, or wash it, like Gold-dust, from among Sand, and other lighter Substances, is to me unknown: However, it is seldom collected perfectly pure; since, among several Parcels of it that I have seen, I constantly observ'd a large Mixture of a shining black Sand, such as is found on the Shores of Virginia and Jamaica, which is a rich iron Ore, and answers to the Magnet. It hath also usually mix'd with it some few shining Particles of a golden Colour, which seem to be a Substance of a different Nature.
It is very probable that there is great Plenty of this Semi-metal in the Spanish West Indies; since Trinkets made of it are there very common. A Gentleman of Jamaica bought five Pounds of it at Carthagena for less than its Weight of Silver; and it was formerly sold for a much lower Price.
When exposed by itself to the Fire, either in Grains, or in larger Pieces, it is of extreme difficult Fusion; and hath been kept for two Hours in an Air-Furnace, in a Heat that would run down cast Iron in fifteen Minutes: Which great Heat it endur'd without being melted or washed; neither could it be brought to fuse in this Heat, by adding it to Borax, and other saline Fluxes. But the Spaniards have a Way of melting it down, either alone, or by means of some Flux; and cast it into Sword-hilts, Buckles, Snuff-boxes, and other Utensils.
When exposed to a proper Degree of Fire, with Lead, Silver, Gold, Copper, or Tin, it readily melts [p. 592=588] and incorporates with these Metals; rendering the Mixture, like itself, extremely hard and brittle.
Having been melted in an Assay-Furnace, on a Test with Lead, and therewith exposed to a great Fire for three Hours, till all the Lead was wrought off, the Platina was afterwards found remaining at the Bottom of the Test, without having suffer'd any Alteration or Diminution by this Operation.
A Piece of Platina was put into strong and pure Aqua fortis, and therewith placed in a Sand-heat for twelve Hours: The Platina, when taken out of the Aqua fortis, was found of the same Weight as when put into it; being in no-wise dissolved or corroded by that Menstruum.
Id had been reported, that this Semi-metal was specifically heavier than Gold; but having weigh'd several Pieces of it hydrostatically in a nice Assay-Balance, I found one of these Pieces to weigh in Air gr. 241/8, and in Water gr. 122/8: So that its specific Gravity was to that of Water exactly as 15:1. Another Piece, that seem'd to be cast very open and porous, I found in Gravity to Water only as 13.91 to 1. Altho' this last mention'd Piece, could it have endur'd the Hammer as well as Gold, might probably have been reduc'd to a considerably greater Degree of Solidity than that of the first-mention'd Specimen. For the purest Gold is seldom found, after Fusion, to come up to its true specific Weight, until it hath been brought up to its greatest Degree of Solidity under the Hammer.
I also weigh'd an equal Mixture of Gold and Platina, which I found nearly as ponderous as Gold itself; the specific Weight of this Mixture being to that of Water as 19 to 1.
[p. 593=589] It has been reported that the Spaniards have sometimes been tempted to adulterate Gold with Platina, as the Mixture could not be distinguish'd from true Gold by all the ordinary Trials: But the Gold thus adulterated was, upon a nicer Examination, found hard and brittle, and could not be separated from the Platina, and render'd ductile and pure, either by Cementation, or by the more ordinary Operations with Lead and Antimony. In order therefore to prevent this Fraud, the King of Spain commanded that the Mines of Platina should be stopped up; so that this Semi-metal is now much scarcer than formerly.
From the foregoing Account it appears, that no known Body approaches nearer to the Nature of Gold, in its most essential Properties of Fixedness and Solidity, than the Semi-metal here treated of; and that it also bears a great Resemblance to Gold in other Particulars. Some Alchemists have thought that Gold differ'd from other Metals in nothing so much as in its specific Gravity; and that, if they could obtain a Body that had the specific Weight of Gold, they could easily give it all the other Qualities of that Metal. Let them try their Action on this Body; which, if it can be made as ductile as Gold, will not easily distinguish'd from Gold itself.
Upon the whole, this Semi-metal seems a very singular Body, that merits an exacter Inquiry into its Nature than hath hitherto been made;since it is not altogether improbable, that, like the Magnet, Iron, Antimony, Mercury, and other metallic Substances, it may be endowed with some peculiar Qualities [p. 590], that may render it of singular Use and Importance to Mankind.

Specimens of Platina presented to the Royal Society.

No. 1 Platina, in Dust, or minute Masses, mixed with Black Sand, and other Impurities, as brought from the Spanish West Indies.
2. Native Platina, separated from the above mention'd Impurities.
3. Platina that has been fused.
4. Another Piece of Platina, that was Part of the Pummel of a Sword.

III. To the Royal Society.

London, Dec. 13, 1750

I beg Leave to subjoin a few Lines to my learned and ingenious Friend Dr. Brownrigg's Paper concerning the Platina di Pinto, or what is likewise call'd in Ameria Juan Blanco. This Substance is mention'd in no Author I have met with, except by our worthy Brother Don Antonia d'Ulloa, who, in the History of his Voyage to South America, Vol. II. Book 6. Chap. 10. which I have here extracted, and translated from the Spanish, when giving an Account of the Gold and Silver Mines in the Province of Quito, and of the various Methods of separating these Metals from other Substances, with which they are combin'd, says, that, "in the Territory of Choco... there are Gold Mines, in which that [p. 590] Metal is so disguised and enveloped with other mineral Substances, Juices, and Stones, that, for their Separation from the Gold, they are obliged to use Quicksilver. Sometimes they find mineral Substances, which, from their being mixed with Platina, they chuse to neglect. This Platina is a Stone (Piedra) of such Resistance, that it is not easily broken by a Blow upon an Anvil. It is not subdued by Calcination, and it is very difficult to extract the Metal it contains even with much Labour and Expence."
In the before mention'd Work, Chap. 11. the same Author, when speaking of the remaining Works of the Indians of old, says, "the Specula wrought out of Stones, which are found in the Places of Worship of the Indians, are of two kinds, in relation to the Matter of which they are made: One of these is call'd Piedra de Inga, the other Piedra de Gallinazo. The first of these is smooth, of a leaden Colour, and not transparent; they are usually found wrought of a circular Figure: One of the Surfaces is plain, and as smooth as though it were made of a kind of Chrystal; the other Surface is oval, or rather somewhat spherical, and not so much burnish'd as the plain one. Although they vary in their Size, they are commonly from three to four inches in Diameter; but he has seen one that was a Foot and half in Diameter. Its principal Surface was concave, and much augmented the Size of Objects, as its Polish, was in as great Perfection as though it had been work'd by a dextrous Artist in these Times.
[p. 588=592] This Stone has certain Veins, or hair-like Appearances, on its Surface; whereby it is render'd less fit for a Speculum, and is apt to break in these Veins in receiving any Blow. May are persuaded, or at least suspect, that the Matter of these is a cast Composition; and although there are some Appearances of this being so, they are not sufficiently convincing. In this Country there are Gullies (Quebradas) where the Mineral of them is found rough, and from whence some are always taken; but these are not now wrought for those Purposes for which heretofore they were employ'd by he Indians: But this is no Reason but that some of them may have been cast, as with the same Material taken out of the Mine, they may have been made artificially, and thereby have receiv'd a greater Degree of Perfection, as well in their Quality as in their Figure." He says further, "that, although at present, these, as well as several other things found there are but of small Value, nevertheless they are extremely curious, and worthy to be esteem'd, as well for their great Antiquity, as for their being the Performances of those barbarous People."
Some of these Piedras de Inga I now take the Liberty of laying before the Society, both in their rough and in their polish'd State. They were brought hither with several other Curiosities from America by that excellent Person, and my much lamented Friend, Don Pedro Maldonado, and were presented by him to our most worthy President, who was pleased to put them into my Hands. They are doubtless of a metalline Substance, and have, in [p. 589=593] my Opinion, evident Marks of having been fused and cast. They very much resemble, as you will see by comparing them, the Platina before mention'd: And though they are call'd (Piedras) Stones by Don Antonio d'Ulloa, he likewise gives the same Appellation to the Platina. I cannot therefore help recommending to some curious Metallurgist of the Society to make the Experiment, whether or no, when the Piedras de Inga are, by a proper Process, divested of their stony and other heterogeneous Parts, the metalline Residuum will not resemble, as well in specific Gravity (for which it is so remarkable) as in other Properties, the purified Platina now before us?
Wm. Watson.


Read Dec. 20, 1750.
In January 1742-3. there were brought from Jamaica, in a Man of War, several Bars (as thought) of Gold, consigned from different Merchants of that Island, to their different Correspondents here, as Bars of Gold. These Bars had the same specific Gravity, or rather more than Gold, and were exactly like that Metal in Colour, Grain &c. A Piece of one of these counterfeit Bars was sent to the Mint to be tested, and it was found to be twenty one Carats three Grains worse than Standard.
Emanuel Mendez da Costa (note).
[p. 594]

V. Extract of a Letter from Wm. Brownrigg M.D. and F.R.S. to Wm. Watson F.R.S. containing some further Experiments upon the Platina.

Read Feb. 28. 1750-51.
Whitehaven, Feb. 13, 1750

I was favour'd with your Letter of Dec. 15, and am much obliged to you for the Trouble you took in presenting my Specimens of the Platina to the Royal Society, together with my Memoir relating thereto; and I thank you for the Addition you made to it of the Extract of Don d'Ulloa's Voyage.
The Gentleman, whose Experiments on Platina I mention'd to the Royal Society, was Mr. Charles Wood, who permitted me to make what Use of them I pleased; and I did not pretend to have made any new Discovery, nor to know so much of that Body, as hath long been known to the Spaniards. I might indeed have made use of his Authority; but he was not ambitious of appearing in Print.
The chief thing about which I had any Difficulty, was what had been asserted of the Platina's resisting the Force of Lead in Coppellation. This Experiment I have tried therefore, by adding to gr. xxvi. of Platina, sixteen times its Weight of pure Lead, that I had myself reduced from Litharge. To the Lead put into a Coppel, and placed in a proper Furnace; as soon as it was melted I added the Platina, which in a short time was dissolved in the Lead. After the Lead was all wrought off, there remain'd at the Bottom of the Coppel a Pellet of Platina, which I found to weigh only gr. xxi.; so that, in [p. 595] this Opinion, the Platina had lost neat a fifth Part of its Weight.
According therefore to this Experiment, the Platina does not wholly resist the Force of Lead in Coppellation; but, by repeated Operations of that kind with larger Quantities of Lead, may probably all be destroy'd: And by such repeated Coppellations, Gold and Silver may very likely be refin'd from it; although what was before asserted may hold pretty true, with regard to the common Coppellation of the Assayers and Refiners.
Mr. Wood said, that, in his Experiment, he thought the Platina rather gain'd than lost, in Weight by Coppellation. This might happen from some small Mixture of Lead, or other Metal continuing with it after it remained no longer fused.
From this single Experiment I will not be quite positive that Lead thus consumes some small Quantity of Platina, since it is possible the Platina used might not be pure. Besides, in order to keep it longer in Fusion, I urged on the Experiment with an uncommon Degree of Heat, especially towards the End of the Operation; although I think no great Error could thence arise; as half a Drachm of Silver, which I coppel'd at the same time, had lost only two Grains in the Operation.
I am told that one Mr. Ord, formerly a Factor to the South Sea Company, took in Payment from some Spaniard; Gold, to the Value of 500 l. Sterling, which being mix'd with Platina, was so brittle, that he could not dispose of it, neither could he get it refin'd in London, so that it was quite useless to him: Altho', if no Error hath been committed [p. 596] in the above-mention'd Experiments, it might probably have been render'd pure by a much larger Dose of Lead than is usually applied for that Purpose.
To my Memoir I might have added, that, attempting to cleanse a Parcel of the native Platina from the black Sand, wherewith it was mixed, I found that a great many of its Grains were attracted by the Magnet I made use of for that Purpose. This Circumstance I took notice of in a Letter to Lord Lonsdale two Years ago. I am,
Dear Sir,
Your most obliged humble Servant,
W. Brownrigg

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