Difference between revisions of "Platinum" - New World Encyclopedia

From New World Encyclopedia
(→‎History: editing)
(→‎Isotopes: moving Isotopes into Notable Characteristics)
Line 75: Line 75:
  
 
== History ==
 
== History ==
Naturally-occurring platinum and platinum-rich alloys have been known for a long time. Though the metal was used by [[pre-Columbian]] Native Americans, the first European reference to platinum appears in 1557 in the writings of the [[Italy|Italian]] humanist [[Julius Caesar Scaliger]] (1484-1558) as a description of a mysterious metal found in Central American mines between Darién ([[Panama]]) and Mexico. It was, in his words, "up until now impossible to melt by any of the Spanish arts."
+
Naturally-occurring platinum and platinum-rich alloys have been known for a long time. Though the metal was used by Native Americans before European influence, the first European reference to platinum appears in 1557, in the writings of the [[Italy|Italian]] humanist Julius Caesar Scaliger (1484-1558) as a description of a mysterious metal found in Central American mines between Darién ([[Panama]]) and Mexico. It was, in his words, "up until now impossible to melt by any of the Spanish arts."
  
The Spaniards named the metal "platina," or little silver, when they first encountered it in Colombia. They regarded platinum as an unwanted impurity in the [[silver]] they were mining and often discarded it.
+
When the Spaniards first encountered platinum in Colombia, they named it "platina," or little silver. They regarded platinum as an unwanted impurity in the [[silver]] they were mining and often discarded it.
  
Platinum was discovered by astronomer [[Antonio de Ulloa]] and Don Jorge Juan y Santacilia (1713-1773), both appointed by King [[Philip V of Spain|Philip V]] to join a geographical expedition in [[Peru]] that lasted from 1735 to 1745. Among other things, Ulloa observed the ''platina del pinto'', the unworkable metal found with gold in [[New Granada]] ([[Colombia]]). British [[privateer]]s intercepted Ulloa's ship on the return voyage. Though he was well-treated in England, and even made a member of the [[Royal Society]] he was prevented from publishing a reference to the unknown metal until 1748. Before that could happen, [[Charles Wood]]* independently isolated the element in 1741.
+
Platinum was discovered by astronomer Antonio de Ulloa and Don Jorge Juan y Santacilia, both appointed by King [[Philip V of Spain|Philip V]] to join a geographical expedition in [[Peru]] that lasted from 1735 to 1745. Among other things, Ulloa observed ''platina del pinto'', an "unworkable" metal found with gold in New Granada ([[Colombia]]). British [[privateer]]s intercepted Ulloa's ship on the return voyage. Though he was well-treated in England, and even made a member of the [[Royal Society]], he was prevented from publishing a reference to the metal until 1748. Before that could happen, [[Charles Wood]]* independently isolated the element in 1741.
  
 
The [[alchemy|alchemical]] symbol for platinum (shown below) was made by joining the symbols of silver and gold.
 
The [[alchemy|alchemical]] symbol for platinum (shown below) was made by joining the symbols of silver and gold.
 
[[image:platinum-symbol.png|left|75px|Alchemical symbol for platinum]]
 
[[image:platinum-symbol.png|left|75px|Alchemical symbol for platinum]]
  
The definition of a [[meter]] was, for a long time, based on the distance between two marks on a bar of a platinum-[[iridium]] alloy housed at the Bureau International des Poids et Mesures in Sèvres, [[France]]. A platinum-iridium cylinder serves to this day as the standard of the [[kilogram]] and is housed in the same facility as the meter bar.
+
For a long time, the definition of a [[meter]] was based on the distance between two marks on a bar of a platinum-[[iridium]] alloy housed at the Bureau International des Poids et Mesures in Sèvres, [[France]]. A platinum-iridium cylinder serves to this day as the standard of the [[kilogram]] and is housed in the same facility as the meter bar.
  
 
== Occurrence ==
 
== Occurrence ==
 
[[Image:PlatinumOreUSGOV.jpg|thumb|left|Platinum ore]]
 
[[Image:PlatinumOreUSGOV.jpg|thumb|left|Platinum ore]]
Platinum is an extremely rare metal, occurring as only 5 [[parts per billion|ppb]] in the [[Earth]]'s [[crust (geology)|crust]].
+
Platinum is an extremely rare metal, occurring as only 5 parts per billion in the [[Earth]]'s [[crust (geology)|crust]]*.
  
Platinum is often found free in areas of the [[Americas]] and [[alloy|alloyed]] with [[iridium]] as [[platiniridium]]. The platinum [[arsenide]], [[sperrylite]] (PtAs<sub>2</sub>), is a major source of platinum associated with [[nickel]] ores in the [[Sudbury Basin]] deposit in [[Ontario]], [[Canada]]. The rare [[sulfide]] mineral [[cooperite]], (Pt,Pd,Ni)S, contains platinum along with [[palladium]] and nickel. Cooperite occurs in the [[Merensky Reef]] within the [[Bushveld complex]], [[Transvaal]], [[South Africa]]. South Africa is the largest producer of platinum in the world.
+
In certain areas of the [[Americas]], platinum is often found free or [[alloy|alloyed]] with [[iridium]] as [[platiniridium]]. Platinum [[arsenide]] (PtAs<sub>2</sub>), also known as ''sperrylite'', is a major source of platinum associated with [[nickel]] ores in the Sudbury Basin deposit in [[Ontario]], [[Canada]]. The rare [[sulfur|sulfide]] mineral cooperite contains platinum, [[palladium]], and nickel. Cooperite occurs in the Merensky Reef within the Bushveld complex in [[Transvaal]], [[South Africa]]. South Africa is the largest producer of platinum in the world.
  
Platinum, often accompanied by small amounts of other [[platinum family]] metals, occurs in [[alluvium|alluvial]] [[Placer mining|placer]] deposits in the [[Witwatersrand]] of South Africa, [[Colombia]], [[Ontario]], the [[Ural Mountains]], and in certain western [[United States|American]] states.
+
Often accompanied by small amounts of other [[platinum family]] metals (see below), platinum occurs in [[alluvium|alluvial]] [[Placer mining|placer]] deposits in the [[Witwatersrand]] of South Africa, [[Colombia]], [[Ontario]], the [[Ural Mountains]], and in certain western [[United States|American]] states.
  
Platinum is produced commercially as a by-product of [[nickel]] ore processing in the Sudbury deposit. The huge quantities of nickel ore processed makes up for the fact that platinum is present as only 0.5 [[parts per million|ppm]] in the ore.
+
Platinum is produced commercially as a by-product of [[nickel]] ore processing in the Sudbury deposit. The huge quantities of nickel ore processed makes up for the fact that platinum is present as only 0.5 parts per million in the ore.
  
 
== Notable characteristics ==  
 
== Notable characteristics ==  
 
[[Image:Platinum nuggets.jpg|left|thumb|An assortment of native platinum nuggets]]
 
[[Image:Platinum nuggets.jpg|left|thumb|An assortment of native platinum nuggets]]
The [[metal]] appears silvery-white when pure, and firm. The metal is [[corrosion]]-resistant. The [[catalyst|catalytic]] properties of the six [[platinum family]] metals are outstanding (a mixture of [[hydrogen]] and [[oxygen]] explodes in the presence of platinum). For this catalytic property, platinum is used in [[catalytic converter]]s, incorporated  in [[automobile]] exhaust systems, as well as tips of [[spark plugs]].
+
The [[metal]] appears silvery-white when pure. The metal is [[corrosion]]-resistant.  
 +
Platinum's wear- and tarnish-resistance characteristics are well suited for making fine [[jewelry]].  Platinum is more precious than [[gold]]. The price of platinum changes along with its availability, but it normally costs about twice as much as gold. In the [[18th century]], platinum's rarity made King [[Louis XV of France]] declare it the only metal fit for a king.
 +
 
  
Platinum's wear- and tarnish-resistance characteristics are well suited for making fine [[jewelry]]. Platinum is more precious than [[gold]]. The price of platinum changes along with its availability, but it normally costs about twice as much as gold. In the [[18th century]], platinum's rarity made King [[Louis XV of France]] declare it the only metal fit for a king.
+
The [[catalyst|catalytic]] properties of the six [[platinum family]] metals are outstanding (a mixture of [[hydrogen]] and [[oxygen]] explodes in the presence of platinum). For this catalytic property, platinum is used in [[catalytic converter]]s, incorporated in [[automobile]] exhaust systems, as well as tips of [[spark plugs]].
  
 
Platinum possesses remarkable resistance to chemical attack, excellent high-temperature characteristics, and stable electrical properties. All these properties have been exploited for industrial applications. Platinum does not [[oxidation|oxidise]] in air at any temperature, but can be corroded by [[cyanide]]s, [[halogen]]s, [[sulfur]], and caustic [[alkali]]s. This metal is insoluble in [[hydrochloric acid|hydrochloric]] and [[nitric acid]], but does dissolve in the mixture known as [[aqua regia]] (forming [[chloroplatinic acid]]). Common [[oxidation state]]s of platinum include +2, +3, and +4.
 
Platinum possesses remarkable resistance to chemical attack, excellent high-temperature characteristics, and stable electrical properties. All these properties have been exploited for industrial applications. Platinum does not [[oxidation|oxidise]] in air at any temperature, but can be corroded by [[cyanide]]s, [[halogen]]s, [[sulfur]], and caustic [[alkali]]s. This metal is insoluble in [[hydrochloric acid|hydrochloric]] and [[nitric acid]], but does dissolve in the mixture known as [[aqua regia]] (forming [[chloroplatinic acid]]). Common [[oxidation state]]s of platinum include +2, +3, and +4.
Line 114: Line 116:
  
  
== Isotopes ==
+
 
Naturally occurring platinum is composed of five stable [[isotope]]s and one [[radioisotope]], Pt-190, which has a very long [[half-life]] (over 6 billion years or 190 [[second|Ps]]). There are also many other [[radioisotope]]s with the most stable being Pt-193 with a half-life of 50 years.
 
  
 
== Precautions ==
 
== Precautions ==

Revision as of 02:59, 16 April 2006

78 iridiumplatinumgold
Pd

Pt

Ds
Pt-TableImage.png
periodic table
General
Name, Symbol, Number platinum, Pt, 78
Chemical series transition metals
Group, Period, Block 10, 6, d
Appearance grayish white
Pt,78.jpg
Atomic mass 195.084(9) g/mol
Electron configuration [Xe] 4f14 5d9 6s1
Electrons per shell 2, 8, 18, 32, 17, 1
Physical properties
Phase solid
Density (near r.t.) 21.45 g/cm³
Liquid density at m.p. 19.77 g/cm³
Melting point 2041.4 K
(1768.3 °C, 3214.9 °F)
Boiling point 4098 K
(3825 °C, 6917 °F)
Heat of fusion 22.17 kJ/mol
Heat of vaporization 469 kJ/mol
Heat capacity (25 °C) 25.86 J/(mol·K)
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k
at T/K 2330 (2550) 2815 3143 3556 4094
Atomic properties
Crystal structure cubic face centered
Oxidation states 2, 3, 4
(mildly basic oxide)
Electronegativity 2.28 (Pauling scale)
Ionization energies 1st: 870 kJ/mol
2nd: 1791 kJ/mol
Atomic radius 135 pm
Atomic radius (calc.) 177 pm
Covalent radius 128 pm
Van der Waals radius 175 pm
Miscellaneous
Magnetic ordering paramagnetic
Electrical resistivity (20 °C) 105 nΩ·m
Thermal conductivity (300 K) 71.6 W/(m·K)
Thermal expansion (25 °C) 8.8 µm/(m·K)
Speed of sound (thin rod) (r.t.) 2800 m/s
Speed of sound (thin rod) (r.t.) 168 m/s
Shear modulus 61 GPa
Bulk modulus 230 GPa
Poisson ratio 0.38
Mohs hardness 3.5
Vickers hardness 549 MPa
Brinell hardness 392 MPa
CAS registry number 7440-06-4
Notable isotopes
Main article: Isotopes of platinum
iso NA half-life DM DE (MeV) DP
190Pt 0.01% 6.5×1011 y α 3.18 186Os
191Pt syn 2.96 d ε ? 191Ir
192Pt 0.79% Pt is stable with 114 neutrons
193mPt syn 4.33 d IT 0.1355e 193Pt
193Pt syn 50 y ε ? 193Ir
194Pt 32.9% Pt is stable with 116 neutrons
195mPt syn 4.02 d IT 0.1297e 195Pt
195Pt 33.8% Pt is stable with 117 neutrons
196Pt 25.3% Pt is stable with 118 neutrons
197mPt syn 1.59 h IT 0.3465 197Pt
197Pt syn 19.8913 h β- 0.719 197Au
198Pt 7.2% Pt is stable with 120 neutrons

Platinum (chemical symbol Pt, atomic number 78) is a silvery grey precious metal, with a monetary value that is higher than that of gold. Highly resistant to corrosion, it is used in jewelry, laboratory equipment, electrical contacts, dentistry, and automobile emissions control devices.

Developing: is a chemical element in the periodic table that has the symbol Pt and atomic number 78. A heavy, malleable, ductile, precious, grey-white transition metal, platinum is resistant to corrosion and occurs in some nickel and copper ores along with some native deposits. ---- Developing.

History

Naturally-occurring platinum and platinum-rich alloys have been known for a long time. Though the metal was used by Native Americans before European influence, 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 mysterious metal found in Central American mines between Darién (Panama) and Mexico. It was, in his words, "up until now impossible to melt by any of the Spanish arts."

When the Spaniards first encountered platinum in Colombia, they named it "platina," or little silver. They regarded platinum as an unwanted impurity in the silver they were mining and often discarded it.

Platinum was discovered by astronomer Antonio de Ulloa and Don Jorge Juan y Santacilia, both appointed by King Philip V to join a geographical expedition in Peru that lasted from 1735 to 1745. Among other things, Ulloa observed platina del pinto, an "unworkable" metal found with gold in New Granada (Colombia). British privateers intercepted Ulloa's ship on the return voyage. Though he was well-treated in England, and even made a member of the Royal Society, he was prevented from publishing a reference to the metal until 1748. Before that could happen, Charles Wood independently isolated the element in 1741.

The alchemical symbol for platinum (shown below) was made by joining the symbols of silver and gold.

Alchemical symbol for platinum

For a long time, the definition of a meter was based on the distance between two marks on a bar of a platinum-iridium alloy housed at the Bureau International des Poids et Mesures in Sèvres, France. A platinum-iridium cylinder serves to this day as the standard of the kilogram and is housed in the same facility as the meter bar.

Occurrence

Platinum ore

Platinum is an extremely rare metal, occurring as only 5 parts per billion in the Earth's crust.

In certain areas of the Americas, platinum is often found free or alloyed with iridium as platiniridium. Platinum arsenide (PtAs2), also known as sperrylite, is a major source of platinum associated with nickel ores in the Sudbury Basin deposit in Ontario, Canada. The rare sulfide mineral cooperite contains platinum, palladium, and nickel. Cooperite occurs in the Merensky Reef within the Bushveld complex in Transvaal, South Africa. South Africa is the largest producer of platinum in the world.

Often accompanied by small amounts of other platinum family metals (see below), platinum occurs in alluvial placer deposits in the Witwatersrand of South Africa, Colombia, Ontario, the Ural Mountains, and in certain western American states.

Platinum is produced commercially as a by-product of nickel ore processing in the Sudbury deposit. The huge quantities of nickel ore processed makes up for the fact that platinum is present as only 0.5 parts per million in the ore.

Notable characteristics

An assortment of native platinum nuggets

The metal appears silvery-white when pure. The metal is corrosion-resistant. Platinum's wear- and tarnish-resistance characteristics are well suited for making fine jewelry. Platinum is more precious than gold. The price of platinum changes along with its availability, but it normally costs about twice as much as gold. In the 18th century, platinum's rarity made King Louis XV of France declare it the only metal fit for a king.


The catalytic properties of the six platinum family metals are outstanding (a mixture of hydrogen and oxygen explodes in the presence of platinum). For this catalytic property, platinum is used in catalytic converters, incorporated in automobile exhaust systems, as well as tips of spark plugs.

Platinum possesses remarkable resistance to chemical attack, excellent high-temperature characteristics, and stable electrical properties. All these properties have been exploited for industrial applications. Platinum does not oxidise in air at any temperature, but can be corroded by cyanides, halogens, sulfur, and caustic alkalis. This metal is insoluble in hydrochloric and nitric acid, but does dissolve in the mixture known as aqua regia (forming chloroplatinic acid). Common oxidation states of platinum include +2, +3, and +4.

Applications

  • catalyst utilized in the catalytic converter, an optional component of the gasoline-fuelled automobile exhaust system (see "Notable characteristics" in this article),
  • certain platinum-containing compounds are capable of intercalating into DNA and are chemotherapeutic agents owing to this capability. For example, cisplatin, carboplatin and oxaliplatin belong to this class of drugs,
  • platinum resistance thermometers,
  • electrodes for use in electrolysis.


Precautions

This metal doesn't normally cause health problems due to its unreactive nature. Platinum compounds rarely occur in nature. Certain platinum complexes (cis-platin) have been used in chemotherapy, as they have very good anti-tumor activity, particularly when used to combat testicular cancer, though they also cause cumulative, irreversible kidney damage.

Rarity and Color

Platinum's rarity as a metal has caused advertisers to associate it with exclusivity and wealth. "Platinum" credit cards have greater privileges than do "gold" ones. "Platinum awards" are the highest possible, ranking above gold, silver and bronze. For example, a musical album that has sold more than 1,000,000 copies, will be credited as "platinum". And some products, such as blenders and vehicles, with a silvery-white colour are identified as "platinum" (a higher certification of "Diamond" does exist, however). Platinum is considered a precious metal, although its use as such is much more rare than the use of gold or silver. The frame of the Crown of Queen Elizabeth the Queen Mother, manufactured for her Coronation as Consort of King George VI is made of platinum. It was the first British Crown to be made of that metal. Due to its rarity, platinum is a highly priced metal, more so than gold or silver.

References
ISBN links support NWE through referral fees

See also

External links

Commons
Wikimedia Commons has media related to::

Credits

New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:

The history of this article since it was imported to New World Encyclopedia:

Note: Some restrictions may apply to use of individual images which are separately licensed.