platinum

The title of this article is ambiguous. Further meanings are listed under platinum (disambiguation) .

properties
[ Xe ] 4 f 14 5 d 9 6 s 1 78 Pt Periodic table
General
Name , symbol , atomic number	Platinum, Pt, 78
Element category	Transition metals
Group , period , block	10 , 6 , d
Appearance	gray-white
CAS number	7440-06-4
EC number	231-116-1
ECHA InfoCard	100.028.287
Mass fraction of the earth's envelope	0.005 ppm
Atomic
Atomic mass	195,084 (9) et al
Atomic radius (calculated)	135 (177) pm
Covalent radius	136 pm
Van der Waals radius	175 pm
Electron configuration	[ Xe ] 4 f 14 5 d 9 6 s 1
1. Ionization energy	8th.95883 (10) eV ≈ 864.4 kJ / mol
2. Ionization energy	18th.56 (12) eV ≈ 1 791 kJ / mol
3. Ionization energy	29.0 (1.6 eV) ≈ 2 800 kJ / mol
4. Ionization energy	43.0 (1.7 eV) ≈ 4 150 kJ / mol
5. Ionization energy	56.0 (1.9) eV ≈ 5 400kJ / mol
Physically
Physical state	firmly
Crystal structure	Cubic area-centered
density	21.45 g / cm³ (20 ° C)
Mohs hardness	3.5
magnetism	paramagnetic ( Χ m = 2.8 10 −4 )
Melting point	2041.4 K (1768.3 ° C)
boiling point	4100 K (3827 ° C)
Molar volume	9.09 · 10 −6 m 3 · mol −1
Heat of evaporation	510 kJ / mol
Heat of fusion	19.6 kJ mol −1
Speed ​​of sound	2680 m · s −1
Specific heat capacity	130 J kg −1 K −1
Work function	5.65 eV
Electric conductivity	9.48 · 10 6 A · V −1 · m −1
Thermal conductivity	72 W m −1 K −1
Chemically
Oxidation states	−2, 0, +2 , +4 , +6
Normal potential	1.118 V (Pt 2+ + 2 e - → Pt)
Electronegativity	2.2 ( Pauling scale )
Isotopes
isotope NH t 1/2 ZA ZE (M eV ) ZP 188 Pt {syn.} 10.2 d ε 0.507 188 Ir 189 Pt {syn.} 10.87 h ε 1,971 189 Ir 190 pt 0.01% 6.5 · 10 11 a α 3.249 186 Os 191 pt {syn.} 2.96 d ε 1.019 191 Ir 192 pt 0.79% Stable 193 pt {syn.} 50 a ε 0.057 193 Ir 194 pt 32.9% Stable 195 pt 33.8  % Stable 196 pt 25.3% Stable 197 pt {syn.} 19.8915 h β - 0.719 197 Au 198 pt 7.2% Stable 199 pt {syn.} 30.80 min β - 1.702 199 Au 200 pt {syn.} 12.5 h β - 0.660 200 Au
For other isotopes see list of isotopes
NMR properties
Spin quantum number I γ in rad · T −1 · s −1 E r  ( 1 H) f L at B = 4.7 T in MHz 195 pt 1/2 5.839 · 10 7 0.00351 21.41
safety instructions
GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
MAK	Switzerland: 1 mg m −3 (measured as inhalable dust )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Platinum ( Germany : [ ˈplaːtiːn ], Austria : [ plaˈtiːn ]) is a chemical element with the element symbol Pt and the atomic number 78. It has a high density and is a precious, malleable, ductile, gray-white transition metal . It has a remarkable resistance to corrosion and is considered a precious metal . In the periodic table it is in group 10, in the old counting part of the 8th subgroup , or nickel group .

Platinum is used to make jewelry , automotive catalysts , laboratory equipment , dental implants used and contact materials. Because of its rarity, only small amounts are extracted each year. It is a little reactive metal and is often found in its metallic form. Some platinum-containing complexes such as cisplatin are used in chemotherapy for certain types of cancer.

history

The name is derived from the Spanish word platina , the negative diminutive of plata "silver". The first European mention comes from the Italian humanist Julius Caesar Scaliger . He describes a mysterious white metal that evaded all attempts at melting. A more detailed description of the properties can be found in a report by Antonio de Ulloa published in 1748 .

Platinum was probably first used around 3000 BC in ancient Egypt . The British researcher Sir William Matthew Flinders Petrie (1853–1942) discovered ancient Egyptian jewelry in 1895 and found that small amounts of platinum were also used.

Platinum was also used by the Indians of South America. It was found as an accompaniment to the extraction of gold dust in the washed gold and could not be explicitly separated. The blacksmiths at that time unconsciously exploited the fact that native platinum grains with gold dust can be welded well in the embers of a charcoal fire fanned with bellows, the gold acting like a solder and, through repeated forging and heating, a relatively homogeneous, light color in the forging heat let produce deformable metal alloy. This could not be melted again and was just as durable as gold, but of a whitish-silver-like color. Even an approximately 15 percent platinum content leads to a light gray color. However, pure platinum was still unknown.

In the 17th century, platinum became a major problem in the Spanish colonies as an annoying material when prospecting for gold. It was thought to be “immature” gold and was thrown back into the rivers of Ecuador . Since it has a specific gravity similar to gold and did not tarnish even in fire, it was used to falsify the same. The Spanish government then issued an export ban. She even considered dumping all the platinum she had received up to then in the sea to forestall and deter platinum smuggling and counterfeiting.

The alchemy of the 18th century was called for, because the differentiation from pure gold and the extraction turned out to be extremely difficult with the techniques of the time. But interest was aroused. In 1748 Antonio de Ulloa published a detailed report on the properties of this metal. In 1750 the English doctor William Brownrigg made purified platinum powder. In 1783, Louis Bernard Guyton de Morveau found a simple process for the industrial production of platinum.

The price of platinum hit an all-time high on March 4, 2008 at $ 2308.80 per troy ounce, and at that time was more than twice as expensive as gold ($ 989.80 per troy ounce). As of December 31, 2018, the troy ounce of platinum was quoted at 794 US dollars, well below the gold price .

Platinum as a mineral and occurrence

Platinum nugget, Konder Mine, Khabarovsk region .

Some platinum nuggets from California (USA) and Sierra Leone

Platinum occurs naturally , i.e. in elemental form, and is therefore recognized as a mineral by the International Mineralogical Association (IMA) . In the systematics of minerals according to Strunz (9th edition) it is in the mineral class of "elements" and the department of "metals and intermetallic compounds", where it is named after the subdivision "platinum group elements" together with iridium , palladium and rhodium forms the unnamed group 1.AF.10 . In the outdated, but still in use, 8th edition , platinum had the system no. I / A.14-70 (elements - metals, alloys, intermetallic compounds).

The so-called Merensky Reef , discovered by Hans Merensky in 1924, made commercial platinum mining economical.

The most important platinum mining nations in 2011 were South Africa with 139 tons (91 percent of the world production of 192 tons was 91 percent), Russia with 26 tons and Canada with 10 tons ( see also: Production by country - platinum ).

So far (as of 2011) platinum has been found at around 380 sites worldwide, including in several regions of Ethiopia , Australia , Brazil , Bulgaria , China , the Democratic Republic of the Congo , Germany , France , Guinea , Indonesia , Ireland , Italy , Japan , Colombia , Madagascar , Mexico , Myanmar , New Zealand , Norway , Papua New Guinea , Philippines , Sierra Leone , Zimbabwe , Slovakia , Spain , Czech Republic , Turkey , the United Kingdom and the United States of America (USA).

Platinum is also found in the form of chemical compounds in numerous minerals. Around 50 platinum minerals are known to date (as of 2011).

Extraction and manufacture

Platinum crystals, obtained through chemical transport reactions in the gas phase.

Metallic platinum (platinum soaps) is practically no longer mined today. There is extensive platinum mining only in the South African Bushveld Complex , also at the Great Dyke in Zimbabwe and in the Stillwater Complex in Montana . The South African mines belong e.g. B. Lonmin , Anglo American Platinum or Impala Platinum .

Sources of platinum are also non-ferrous metal production (copper and nickel) in Greater Sudbury (Ontario) and Norilsk (Russia). The platinum group metals are obtained here as a by-product of nickel refining . Platinum metal is the name given to five metals whose chemical behavior is so similar to platinum that separation and pure representation used to make great difficulties. In 1803 iridium , osmium , palladium and rhodium were discovered; Ruthenium followed in 1844 .

Platinum sponge is formed when ammonium hexachloroplatinate (IV) (NH ₄ ) ₂ [PtCl ₆ ] is annealed or when paper that is soaked with platinum salt solutions is heated.

To recycle platinum, it is either dissolved oxidatively in aqua regia , a mixture of nitric and hydrochloric acid, or in a mixture of sulfuric acid and hydrogen peroxide . Platinum is then present in these solutions in the form of complex compounds (e.g. in the case of aqua regia as hexachloroplatinic acid ) and can be recovered from it by reduction . Researchers at National Chung Hsiang University (Taiwan) have developed a novel process in which platinum is electrochemically dissolved in a mixture of zinc chloride and a special ionic liquid . An ionic liquid is an organic salt that is already molten at temperatures below 100 ° C and has a high conductivity. The used platinum is used in the form of an electrode, which is connected as an anode , and the surrounding ionic liquid is heated to around 100 ° C. The platinum dissolves oxidatively. The dissolved platinum can then be deposited again as pure metal on a carrier electrode.

properties

Physical Properties

Platinum is a corrosion-resistant , malleable and soft heavy metal.

Due to its high durability, tarnish resistance and rarity , platinum is particularly suitable for the production of high-quality jewelry.

In powder form, depending on the grain size, platinum is gray (production- related after the decomposition of (NH ₄ ) ₂ [PtCl ₆ ]) to black (platinum black), odorless and flammable. The metal in compact form is not flammable.

Chemical properties

Like the other metals of the platinum group, platinum shows contradicting behavior. On the one hand it is chemically inert, as is typical of noble metals , on the other hand it is highly reactive, catalytically selective towards certain substances and reaction conditions. Platinum shows stable behavior even at high temperatures. It is therefore of interest for many industrial applications.

Platinum dissolves in hot aqua regia.

It is insoluble in hydrochloric and nitric acid alone. In hot aqua regia , a mixture of hydrochloric and nitric acid, it is attacked with the formation of red-brown hexachloroplatinum (IV) acid . However, platinum is also strongly attacked by hydrochloric acid in the presence of oxygen and by hot, smoking nitric acid. Platinum is also attacked by alkali, peroxide, nitrate, sulfide, cyanide and other molten salts. Many metals form alloys with platinum , for example iron , nickel , copper , cobalt , gold , tungsten , gallium , tin, etc. It should be emphasized that platinum sometimes reacts to form compounds with hot sulfur , phosphorus , boron , silicon , carbon in any form , that means also in hot flame gases. Many oxides also react with platinum, which is why only certain materials can be used as crucible material. When melting the metal with a propane- oxygen flame, for example, a neutral to slightly oxidizing flame must be used. The best option is the flame-free electrical-inductive heating of the melting material in zirconium oxide ceramics .

Catalytic properties

Both hydrogen , oxygen and other gases are bound by platinum in the activated state. It therefore has remarkable catalytic properties; In its presence, hydrogen and oxygen react explosively to form water . It is also the catalytically active species in catalytic reforming . However, platinum catalysts quickly become inactive (poisoned) due to aging and contamination and must be regenerated. Porous platinum, which has a particularly large surface, is also known as a platinum sponge . The large surface area results in better catalytic properties. Also, due to the large surface area formerly metallic platinum was deposited on asbestos ( platinum asbestos used), and as a catalyst. Today platinum-quartz wool is used for this purpose because of the asbestos problem .

use

Because of their availability and excellent properties, there are numerous different areas of application for platinum and platinum alloys. Platinum is a favored material for the manufacture of laboratory equipment because it does not produce any flame color . There are z. B. thin platinum wires are used to hold fabric samples in the flame of a Bunsen burner .

Platinum is also used in an almost unmanageable number of areas:

• Platinum is a noble and valuable metal - it is almost sixty times more expensive than silver . It was and is therefore used for expensive jewelry and pens , but also as a means of payment or investment . For these purposes, platinum, like gold, is used in the form of alloys, as it is hardly harder than gold in its pure state. The investment coins Platinum Canadian Maple Leaf and American Platinum Eagle are still issued today. In Russia , between 1828 and 1846, platinum coins were minted, the platinum ruble . Initially there were coins made of around 10.3 grams of platinum with a value of 3 rubles , later coins of double and quadruple value and the corresponding platinum weight were added. Furthermore, the Austrian Mint issued a bullion coin with the motif of the Vienna Philharmonic with one ounce of pure platinum (999.5 ‰) with a face value of 100 euros.
• Thermocouples
• Resistance thermometer (e.g. Pt100)
• Heating resistors
• Contact materials and electrodes, e.g. B. in spark plugs
• Catalysts . Examples are not only vehicle catalytic converters including diesel oxidation catalytic converters and catalytic converters in fuel cells , but also those for large-scale industrial processes such as nitric acid production and platinum-rhodium alloys. A historically important example is the Döbereinersche lighter . In 2005, the consumption of platinum for catalyst production is estimated at 3.86 million ounces , which corresponds to approximately 120.1 tons.
• Magnetic materials
• Chemical apparatus construction, laboratory and analysis equipment
• Crucible for glass production
• Fused glass alloys
• Medical implants , alloy addition in dental materials (see also: Biomaterial )
• Pacemaker
• Thrusters, rocket fairings
• Spinnerets
• Platinum mirrors (mirrors and partially transparent mirrors that, in contrast to silver mirrors, cannot tarnish)
• Laser printer (charging corona)
• Coatings for turbine guide vanes in aircraft engines
• Platinum equipment for special glass melting. Thousands of devices are made from platinum materials for optical and technical special glass melting. From laboratory crucibles made of pure Pt, PtIr, PtRh or PtAu materials for the first test melts to complete continuous tub systems that can weigh several 100 kg of platinum. In addition to the refining chambers, crucibles and pipe systems made of PtIr or PtRh, additional devices such as stirrers, lids, electrodes, discharge rings and nozzles are also used.

The most common material for the devices for the production of optical glass is pure Pt or Pt with 0.3 to 1.0% Ir for the crucibles and pipe systems as well as PtRh ₃ to PtRh ₁₀ for highly mechanically stressed devices such as stirrers.

PtRh ₁₀ to PtRh ₃₀ materials are used in the devices for the production of technical glass . These mechanically more stable, high-percentage PtRh materials cannot be used in the optical glass melt, since the Rh leaves a slightly yellowish color in the melt, which leads to transmission losses in the optical glass products.

(For specific applications also FKS f a k orn s tabilisierte) and ODS (oxide dispersion-strengthened alloy) -Materials employed in the optical and technical specialty glass melt. These Pt, PtRh, PtIr and PtAu materials produced by powder metallurgy are doped with approx. 0.2% yttrium or zirconium oxide in order to prevent premature grain growth in the platinum devices in the glass melting process.

The main problem when machining these materials is the limited weldability in the manufacture of the equipment.

• In contrast to the above-mentioned uses which use platinum as the metal, there is also a highly effective and therefore important class of anti- cancer drugs ( cytostatic agents ) which contain platinum compounds , for example cisplatin , carboplatin and oxaliplatin .

The international kilogram prototype , which is kept in a safe of the Bureau International des Poids et Mesures (BIPM), consists of an alloy of 90% platinum and 10% iridium.

The international meter prototype from 1889 , which defined the meter until 1960, is made from the same alloy .

According to Note 4.B to Chapter 71, platinum, iridium , osmium , palladium , rhodium and ruthenium are considered to be platinum in the sense of the combined nomenclature .

Alloys / materials

Compositions of platinum alloys

designation	Platinum content	Other elements	Comment / use
Set platinum	96%	4% palladium	Melting point: 1750 ° C, density: 20.8 g / cm³, Brinell hardness : 55, tensile strength : 314 N / mm², elongation at break : 39 / jewelry industry
Jewelry platinum	96%	4% copper	Melting point: 1730 ° C, density: 20.3 g / cm³, Brinell hardness: 110, tensile strength: 363 N / mm², elongation at break: 25 / jewelry industry
Pt1Ir	99%	1% iridium	Manufacture of devices for optical glass melting
Pt3Ir	97%	3% iridium	Manufacture of agitators for optical glass melting
Pt5Rh	95%	5% rhodium	Manufacture of agitators for optical glass melting
Pt10Rh	90%	10% rhodium	Manufacture of equipment for technical glass melting
Pt20Rh	80%	20% rhodium	Manufacture of equipment for technical glass melting
Pt30Rh	70%	30% rhodium	Manufacture of equipment for technical glass melting
FKS Pt	99.8%	0.2% zirconium oxide	Manufacture of devices for optical glass melting
FKS Pt10Rh	89.8%	10% rhodium, 0.2% zirconium oxide	Manufacture of equipment for technical glass melting
ODS Pt	99.8%	0.2% yttria	Manufacture of devices for optical glass melting
ODS Pt10Rh	89.8%	10% rhodium, 0.2% yttria	Manufacture of equipment for technical glass melting
ODS Pt20Rh	79.8%	20% rhodium, 0.2% yttria	Manufacture of equipment for technical glass melting

The ODS and FKS materials have roughly the same physical properties, but are made with yttrium or zirconium oxide for patent reasons.

These alloys are used by specialty glass manufacturers such as Hoya and Asahi in Japan, Corning in the USA, Saint-Gobain in France and Schott in Germany for countless devices in glass melting technology.

links

• Platinum (IV) oxide hydrate (PtO ₂  · x H ₂ O) brown-black powder, has extensive applications as a catalyst in organic chemistry
• Platinum (VI) oxide (PtO ₃ )
• Platinum (II) chloride (PtCl ₂ ), platinum (IV) chloride (PtCl ₄ )
• Tetrachloroplatinum (II) acid (H ₂ [PtCl ₄ ])
• Hexachloridoplatinum (IV) acid (H ₂ [PtCl ₆ ])
• Platinum (IV) fluoride (PtF ₄ )
• Platinum (V) fluoride (PtF ₅ )
• Platinum (VI) fluoride (PtF ₆ )
• Platinum (II) bromide (PtBr ₂ )
• Platinum (IV) bromide (PtBr ₄ )
• Platinum (II) iodide (PtI ₂ )
• Platinum (IV) iodide (PtI ₄ )
• Platinum (II) oxide (PtO)
• Platinum (II) sulfide (PtS)

An example of a compound with platinum in oxidation state 0 is

• Tetrakis (triphenylphosphine) platinum (Pt (PPh ₃ ) ₄ )

Compounds with silicon (e.g. for infrared cameras):

• Platinum silicide PtSi
• Pt ₂ Si
• Pt ₃ Si

Connections with aluminum :

• PtAl ₂ is a crystalline, brittle, golden yellow compound
• Pt ₃ Al is also crystalline, but silver

Platinum as an anion Pt ²⁻ :

• Cesium platinum Cs ₂ Pt

Platinum price

→ Main article : Platinum price

The name for platinum, which is traded on the stock exchange, is XPT. The international securities identification number (ISIN) in exchange trading is XC0009665545.

literature

Older literature

• A. Gutbier, Fr. Bauriedel: About platinum. In: Reports of the German Chemical Society. 42 (4), 1909, pp. 4243-4249, doi: 10.1002 / cber.19090420406 .
• H. Rabe: Platin and the Tentelew Chemical Factory. Zeitschrift für Angewandte Chemie 39 (46), 1926, pp. 1406-1411, doi: 10.1002 / anie.19260394606 .
• W. Manchot, G. Lehmann: About monovalent platinum. Reports of the German Chemical Society (A and B Series), 63 (10), 1930, pp. 2775-2782, doi: 10.1002 / cber.19300631016 .

Current literature

• Platinum. The most precious of all precious metals History, production, application. In: Metall (Berlin). 57 (12), 2003, pp. 777-784, ISSN  0026-0746 .
• Michael Groß: When the platinum ruble was rolling. In: Chemistry in Our Time . 38 (5), 2004, p. 308, doi: 10.1002 / ciuz.200490074 .
• Ingo Ott, Ronald Gust: Medicinal chemistry of platinum complexes: special features of inorganic cytostatics. In: Pharmacy in our time . 35 (2), 2006, pp. 124-133, doi: 10.1002 / pauz.200500161 .
• The platinum reference: The classic Pt100 turns 100. In: Electronics Industry. 37 (5), 2006, pp. 44-45, ISSN  0174-5522 .

Web links

Wiktionary: Platinum  - explanations of meanings, word origins, synonyms, translations

Commons : Platinum  - collection of images, videos, and audio files

• Mineral Atlas: Platinum (Wiki)

Individual evidence

1. ^ Harry H. Binder: Lexicon of the chemical elements. S. Hirzel Verlag, Stuttgart 1999, ISBN 3-7776-0736-3 .
2. ↑ The values ​​for the properties (info box) are taken from www.webelements.com (platinum) , unless otherwise stated .
3. ↑ CIAAW, Standard Atomic Weights Revised 2013 .
4. ↑ ^{a b c d e} entry on platinum in Kramida, A., Ralchenko, Yu., Reader, J. and NIST ASD Team (2019): NIST Atomic Spectra Database (ver. 5.7.1) . Ed .: NIST , Gaithersburg, MD. doi : 10.18434 / T4W30F ( https://physics.nist.gov/asd ). Retrieved June 13, 2020.
5. ↑ ^{a b c d e} entry on platinum at WebElements, https://www.webelements.com , accessed on June 13, 2020.
6. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Properties of the Elements and Inorganic Compounds, pp. 4-26.
7. ↑ Robert C. Weast (Ed.): CRC Handbook of Chemistry and Physics . CRC (Chemical Rubber Publishing Company), Boca Raton 1990, ISBN 0-8493-0470-9 , pp. E-129 to E-145. Values ​​there are based on g / mol and given in cgs units. The value specified here is the SI value calculated from it, without a unit of measure.
8. ↑ ^{a b} Yiming Zhang, Julian RG Evans, Shoufeng Yang: Corrected Values ​​for Boiling Points and Enthalpies of Vaporization of Elements in Handbooks. In: Journal of Chemical & Engineering Data . 56, 2011, pp. 328-337, doi: 10.1021 / je1011086 .
9. ↑ Ludwig Bergmann, Clemens Schaefer, Rainer Kassing: Textbook of Experimental Physics. Vol. 6: Solids. 2nd Edition. Walter de Gruyter, 2005, ISBN 3-11-017485-5 , p. 361.
10. ↑ Platinum: substance properties on: http://www.periodensystem.info/
11. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Molecular Structure and Spectroscopy, pp. 9-98.
12. ↑ ^{a b c} Entry on platinum, powder in the GESTIS substance database of the IFA , accessed on April 25, 2017(JavaScript required) .
13. ↑ Schweizerische Unfallversicherungsanstalt (Suva): Limit values ​​- current MAK and BAT values (search for 7440-06-4 or platinum ), accessed on November 25, 2019.
14. ↑ Mindat - Localities for Platinum .
15. ↑ Webmineral - Mineral Species sorted by the element Pt (Platinum) .
16. ^ RT Jones: Platinum Smelting in South Africa. on: www.pyrometallurgy.co.za (English).
17. ↑ Jing-Fang Huang, Hao-Yuan Chen: Heat-Assisted Electrodissolution of Platinum in an Ionic Liquid. In: Angewandte Chemie. 124, 2012, pp. 1716-1720, doi: 10.1002 / anie.201107997 .
18. ↑ Current raw material prices .
19. ↑ Philharmonic Platinum