Editing Platinum (section)

==History==

===Early uses===
Archaeologists have discovered traces of platinum in the gold used in ancient Egyptian burials. For example, a small box from burial of [[Shepenupet II]] was found to be decorated with gold-platinum hieroglyphics.<ref>{{cite journal|title=Sur les métaux égyptiens: Présence du platine parmi les caractères d'inscriptions hiéroglyphiques, confié à mon examn|trans-title=On Egyptian metals: Presence of platinum among the characters of hieroglyphic inscriptions, entrusted to my examination|url=https://gallica.bnf.fr/ark:/12148/bpt6k30888/f778.image|journal=Comptes rendus de l'Académie des Sciences|language=fr|last=Berthelot|first=M.|volume=132|year=1901|page=729}}</ref> However, the extent of early Egyptians' knowledge of the metal is unclear. It is quite possible they did not recognize there was platinum in their gold.<ref>{{cite book |title=Jewelrymaking Through History: An Encyclopedia |pages=155–6 |author=Rayner W. Hesse |date=2007 |publisher=Greenwood Publishing Group |isbn=978-0-313-33507-5}}</ref><ref>{{cite journal | last=Ogden | first=Jack M. | title=The So-Called 'Platinum' Inclusions in Egyptian Goldwork | journal=The Journal of Egyptian Archaeology | publisher=SAGE Publications | volume=62 | issue=1 | year=1976 | issn=0307-5133 | doi=10.1177/030751337606200116 | pages=138–144| s2cid=192364303 }}</ref>

The metal was used by Native Americans near modern-day [[Esmeraldas, Ecuador]] to produce artifacts of a white gold-platinum alloy. Archeologists usually associate the tradition of platinum-working in South America with the [[Pre-Columbian Ecuador#La Tolita Culture|La Tolita Culture]] ({{circa|600}} BCE – 200 CE), but precise dates and location are difficult, as most platinum artifacts from the area were bought secondhand through the [[antiquities trade]] rather than obtained by direct archeological excavation.<ref>{{cite journal|journal=Platinum Metals Review|author=David A. Scott and Warwick Bray|year=1980|url=https://www.technology.matthey.com/article/24/4/147-157/|title=Ancient Platinum Technology in South America: Its use by the Indians in Pre-Hispanic Times|volume=24 |issue=4 |pages=147–157 |doi=10.1595/003214080X244147157 |access-date=5 Nov 2018}}</ref> To work the metal, they would combine gold and platinum powders by [[sintering]]. The resulting gold–platinum alloy would then be soft enough to shape with tools.<ref>{{cite journal | last=Bergsøe | first=Paul | title=Metallurgy of Gold and Platinum among the Pre-Columbian Indians | journal=Nature | publisher=Springer Science and Business Media LLC | volume=137 | issue=3453 | year=1936 | issn=0028-0836 | doi=10.1038/137029a0 | pages=29| bibcode=1936Natur.137...29B | s2cid=4100269 | doi-access=free }}</ref><ref>{{cite journal | last1=Meeks | first1=N. | last2=La Niece | first2=S. | last3=Estevez | first3=P. | title=The technology of early platinum plating: a gold mask of the La Tolita culture, Ecuador | journal=Archaeometry | publisher=Wiley | volume=44 | issue=2 | year=2002 | issn=0003-813X | doi=10.1111/1475-4754.t01-1-00059 | pages=273–284}}</ref> The platinum used in such objects was not the pure element, but rather a naturally occurring mixture of the [[platinum group]] metals, with small amounts of palladium, rhodium, and iridium.<ref name="history">{{cite book|title=A History of Platinum and its Allied Metals|pages=7–8|author=Donald McDonald, Leslie B. Hunt|date=1982|publisher=Johnson Matthey Plc|isbn=978-0-905118-83-3}}</ref>

===European discovery===
The first European reference to platinum appears in 1557 in the writings of the [[Italy|Italian]] humanist [[Julius Caesar Scaliger]] as a description of an unknown noble metal found between [[Darién Province|Darién]] and Mexico, "which no fire nor any Spanish artifice has yet been able to liquefy".<ref name="weeks">{{cite book| title = Discovery of the Elements| url = https://archive.org/details/discoveryofeleme07edunse| url-access = registration|pages = [https://archive.org/details/discoveryofeleme07edunse/page/385 385]–407|author = Weeks, M. E.|date= 1968|edition = 7th|publisher = Journal of Chemical Education| isbn = 978-0-8486-8579-9| oclc = 23991202}}</ref> From their first encounters with platinum, the Spanish generally saw the metal as a kind of impurity in gold, and it was treated as such. It was often simply thrown away, and there was an official decree forbidding the [[adulteration]] of gold with platinum impurities.<ref name="history" />

[[File:Platinum symbol.svg|thumb|left|upright=0.4|alt=A left-pointing crescent, tangent on its right to a circle containing at its center a solid circular dot|This [[alchemical symbol]] for platinum was made by joining the [[symbols]] of [[silver]] ([[moon]]) and [[gold]] ([[sun]]).]]
[[File:Almirante Antonio de Ulloa.jpg|thumb|[[Antonio de Ulloa]] is credited in European history with the discovery of platinum.]]

In 1735, [[Antonio de Ulloa]] and [[Jorge Juan y Santacilia]] saw Native Americans mining platinum while the Spaniards were travelling through Colombia and Peru for eight years. Ulloa and Juan found mines with the whitish metal nuggets and took them home to Spain. Antonio de Ulloa returned to Spain and established the first mineralogy lab in Spain and was the first to systematically study platinum, which was in 1748. His historical account of the expedition included a description of platinum as being neither separable nor [[calcination|calcinable]]. Ulloa also anticipated the discovery of platinum mines. After publishing the report in 1748, Ulloa did not continue to investigate the new metal. In 1758, he was sent to superintend mercury mining operations in [[Huancavelica]].<ref name="weeks" />

In 1741, [[Charles Wood (ironmaster)|Charles Wood]],<ref>{{cite book |url = https://books.google.com/books?id=525bAAAAQAAJ&pg=PP7 |page = 52 |title = The literary life of William Brownrigg. To which are added an account of the coal mines near Whitehaven: And Observations on the means of preventing epidemic fevers |last1 = Dixon |first1 = Joshua |last2 = Brownrigg |first2 = William |date = 1801 |url-status = live |archive-url = https://web.archive.org/web/20170324090058/https://books.google.com/books?id=525bAAAAQAAJ&pg=PP7 |archive-date = 24 March 2017 |df = dmy-all }}</ref><!--https://books.google.com/books?id=S1lFAAAAcAAJ&pg=PA672--> a British [[metallurgy|metallurgist]], found various samples of Colombian platinum in Jamaica, which he sent to [[William Brownrigg]] for further investigation.

In 1750, after studying the platinum sent to him by Wood, Brownrigg presented a detailed account of the metal to the [[Royal Society]], stating that he had seen no mention of it in any previous accounts of known minerals.<ref>{{cite journal |pages = 584–596 |doi = 10.1098/rstl.1749.0110 |title = Several Papers concerning a New Semi-Metal, Called Platina; Communicated to the Royal Society by Mr. Wm. Watson F. R. S |date = 1749 |last1 = Watson |first1 = Wm |last2 = Brownrigg |first2 = William |journal = Philosophical Transactions |volume = 46 |issue = 491–496 |df = dmy-all |bibcode = 1749RSPT...46..584W |s2cid = 186213277 |doi-access = free }}</ref> Brownrigg also made note of platinum's extremely high melting point and refractoriness toward [[borax]].{{clarify|reason=what is meant by "refractoriness towards borax??|date=May 2014}} Other chemists across Europe soon began studying platinum, including [[Andreas Sigismund Marggraf]],<ref>{{cite book | url = https://books.google.com/books?id=GWNQAAAAcAAJ | title = Versuche mit dem neuen mineralischen Körper Platina del pinto genannt | last1 = Marggraf | first1 = Andreas Sigismund | date = 1760 | url-status = live | archive-url = https://web.archive.org/web/20170324173956/https://books.google.com/books?id=GWNQAAAAcAAJ | archive-date = 24 March 2017 | df = dmy-all }}</ref> [[Torbern Bergman]], [[Jöns Jakob Berzelius]],<!--http://www.google.de/url?sa=t&rct=j&q=pmr-v23-i4-155-156&source=web&cd=4&ved=0CFoQFjAD&url=http%3A%2F%2Fwww.platinummetalsreview.com%2Fpdf%2Fpmr-v23-i4-155-156.pdf&ei=FxWTT_6YOoOLswaKy7XeBA&usg=AFQjCNFn8__okV3fK4xcNSg1bQ-Nm_NZHg--> [[William Lewis (scientist)|William Lewis]],<!--http://www.google.de/url?sa=t&rct=j&q=platina+William+Lewis&source=web&cd=1&ved=0CC4QFjAA&url=http%3A%2F%2Fwww.platinummetalsreview.com%2Fpdf%2Fpmr-v7-i2-066-069.pdf&ei=hhWTT4-YNozLsgb14LGLBA&usg=AFQjCNHCECiLbEjXypnkLTujKyMs47FANQ--> and [[Pierre Macquer]]. In 1752, [[Henrik Teofilus Scheffer|Henrik Scheffer]] published a detailed scientific description of the metal, which he referred to as "white gold", including an account of how he succeeded in fusing platinum ore with the aid of [[arsenic]]. Scheffer described platinum as being less pliable than gold, but with similar resistance to corrosion.<ref name="weeks" />

===Means of malleability===
[[Karl von Sickingen]] researched platinum extensively in 1772. He succeeded in making [[malleable]] platinum by [[alloy]]ing it with gold, dissolving the alloy in hot ''[[aqua regia]]'', precipitating the platinum with [[ammonium chloride]], igniting the ammonium chloroplatinate, and hammering the resulting finely divided platinum to make it cohere. [[Franz Karl Achard]] made the first platinum crucible in 1784. He worked with the platinum by fusing it with arsenic, then later [[volatilisation|volatilizing]] the arsenic.<ref name="weeks" />

Because the other platinum-family members were not discovered yet (platinum was the first), Scheffer and Sickingen made the false assumption that due to its hardness—which is slightly more than for pure [[iron]]—platinum would be a relatively non-pliable material, even brittle at times, when in fact its ductility exceeds that of gold and its malleability similar to gold's. Their assumptions could not be avoided because the platinum they experimented with was highly contaminated with minute amounts of platinum-family elements such as [[osmium]] and [[iridium]], amongst others, which embrittled the platinum alloy. Alloying this impure platinum residue called "plyoxen"{{Citation needed|date=October 2022}} with gold as the only solution at the time to obtain a pliable compound. Presently, very pure platinum is readily available, and extremely long wires can easily be drawn from pure platinum due to its crystalline structure, which is similar to that of many soft metals.<ref>[http://mysite.du.edu/~jcalvert/phys/platinum.htm Platinum] {{webarchive|url=https://web.archive.org/web/20111222044410/http://mysite.du.edu/%7Ejcalvert/phys/platinum.htm |date=22 December 2011 }}. mysite.du.edu</ref>

=== "Platinum age" in Spain ===
In 1786, [[Charles III of Spain]] provided a library and laboratory to [[Pierre-François Chabaneau]] to aid in his research of platinum. Chabaneau succeeded in removing various impurities from the ore, including gold, mercury, lead, copper, and iron. This led him to believe he was working with a single metal, but in truth the ore still contained the yet-undiscovered platinum-group metals. This led to inconsistent results in his experiments. At times, the platinum seemed malleable, but when it was alloyed with iridium, it would be much more [[brittle]]. Sometimes the metal was entirely incombustible, but when alloyed with osmium, it would volatilize. After several months, Chabaneau succeeded in producing 23&nbsp;kilograms of pure, malleable platinum by hammering and compressing the sponge form while white-hot. Chabeneau realized the infusibility of platinum would lend value to objects made of it and so started a business with Joaquín Cabezas producing platinum ingots and utensils. This started what is known as the "platinum age" in Spain.<ref name="weeks" />