metals description

Aluminium

2011-06-03T22:09:00.000-07:00

I. INTRODUCTION

1.1 Background
Aluminum is an element with the symbol Al, numbered
atoms 13 and an element of group III A. Physically aluminum
is a silvery white metal with a character like the metal on
Generally, aluminum metal to reflect light, non-toxic,
non-magnetic and not shiny. Aluminimum is one
from 8 major element in the earth's crust, is an element of the 3rd
most abundant in nature that is about 8.1% weight.
Aluminium is not found in nature in the form of metal
pure but in the form of bauxite which still contain
Fe2O3, and Si2O3. That required further processing to
obtain pure aluminum commonly used and sold
commercially
Aluminum is a good electrical conductor, heat resistant
and corrosion resistant. Aluminum is used in many ways.
Most are used as high-voltage cable, material
aircraft construction and household appliances such as pots, bottles
soft drinks and milk bottle caps. Aluminum is usually also
used to coat the lights and compact disks. Compound
Aluminium also has a very broad application. For example
Aluminium sulphate is used for water purification.
1.2 Problem Formulation
The problem that we adopted in this paper
among others:
1. How Aluminum element abundance in nature?
2. How does the whole process being undertaken to
obtain aluminum from bauxite?
3. How to use an aluminum element in life? 3

II. DISCUSSION
2.1 Aluminium in Natural Abundance
Aluminum is one of the abundant element in nature
especially on the earth's crust, which is about 8.1% weight. Although
abundant, but the aluminum metal is never
found in the pure metal in nature. Rather joined
elements - other elements to form a mineral. For example compounds
with a group of silicate which is usually called feldspar, which is
The most abundant mineral in the earth's crust. One type
aluminum silicate mineral that is piropilit AlSi2O5 (OH), addition,
usually combined with manganese to form a mineral called
spesartin, Mn3Al2 (SiO4) 3. Aluminum silicate containing Floride
or hydroxide, Al2SiO4 (F, OH) 2, forming a mineral gem
called topaz, aluminum silicate with potassium named
mikrolin, KAlSi3O8, which is usually green apples until
brown (Navy, 2009).
Aluminum oxide, Al2O3, called alumina and there in the wild
as the mineral corundum. Korumdum containing impurities
Emery called, which is used as a scourer bisasanya
and wheels. Pure corundum is colorless, but with the
some impurities will make the colored korumdum.
For example, with chromium oxide impurities will produce a color
called Ruby red stone, with titanium oxide will be obtained
sapphires are usually colored blue. Aluminum and magnesium
would produce spinel oxide minerals, join the phosphate will
produce mineral varisit, AlPO4.2H2O, which produces color
green and very popular as ornamental stone manufacture
(Navy, 2009).
Aluminum oxide compound of the most common are bauxite, or
pure aluminum containing aluminum oxide in jumlah4
large. Usually a combination of aluminum and oxygen
with formula Al2O3.2H2O. in bauxite is also found several
impurities such as Fe2O3 and SiO2. Therefore, to obtain
pure aluminum metal required more processing bauxite
information. (Davydson, 2009).
Bauxite reserves are scattered throughout the world. State - State
have a source of bauxite in large numbers include: Australia,
Brazil, Guinea, and Jamaica. About 85% of the total bauxite
mined from the earth's crust, is used to produce metal
aluminum, which will be used as raw material products
- Other products are more varied. The remaining approximately 15% used
for sustainable chemical processes at the factory - the factory in
pembutan pesenyawaan aluminum dengn particular purpose (Davydson,
2009).
Map of the World Bauxite Mine
http://www.hs.wisd.org/ddaughenbau
gh/Picture5
2.2 Process Isolation of Aluminum from Bauxite
In general, to obtain pure aluminum from bauxite
done in 2 stages of the process, namely Bayer process and Hall-Heroult process.
In the Bayer process, bauxite is purified to obtain aluminum
oxide. The next process, process-Heroult Hall, melt aluminum
dioxide to obtain pure aluminum metal (Anonymous, 2007).
The Bayer process
In general, the Bayer process consists of 3 stages. Namely: extraction,
Precipitation and Calcination (Anonymous, 2009). In the process of extraction,
bauxite is mechanically crushed and then dissolved in
hot sodium hydroxide solution at 175 milk
o
C, this will pelarutsn
dissolve the aluminum oxide to aluminum hydroxide, Al (OH) 3.
With OH
-
excess will produce [Al (OH) 4]
í
.
Al2O3 + 2 OH
í
+ 3 H2O L 2 [Al (OH) 4]
í
Other components in addition to aluminum oxide (impurities) are not soluble.
So that the aluminum oxide from bauxite will be separated from
pengotornya like Fe2. Separation can be done by filtering
to the insoluble solid impurities, called Red Mud. After
separated by an insoluble pengotornya, get in on the process
precipitation. Filtrate solution containing the aluminum hydroxide is cooled,
so that the resulting dense white precipitate shaped like a thread -
yarn. The next stage of calcination, where the solid white
aluminum hydroxide is heated to a temperature of 1050 ±
o
C, at proses6
This heating aluminum hydroxide will decompose
into alumina, and produces water vapor in the process
(Anonymous, 2009):
2 Al (OH) 3 L Al2O3 + 3 H2O
Bayer Prose By Gradual:
· Bauxite is mechanically crushed, then mixed
with caustic soda (NaOH), the resulting aqueous suspension
contain a wide variety of pure particles.
· Suspense liquid is pumped into the digester (which serves Tank
such as pressure control tube). Solution
heated to a temperature of 230-520 ° F (110-270 ° C) under
pressure of 50 lb / in
2
(340 kPa). In this condition, done
for about half an hour or up to several hours. In
the process is carried out for the addition of caustic soda
ensure that all of the aluminum compound
contained dissolved.
· Hot solution, which becomes a solution of sodium aluminate,
passed through several flash tanks that reduce
merocovery pressure and heat that can be reused
for the purification process.
· The solution is pumped into the settling tank.
on this tank, impurities will precipitate insoluble
under the tank. So that the solution contains only
aluminum oxide dissolved in caustic soda. Residue
which is under the tank (the so-called "Red Mud")
containing fine sand, iron oxide, oxide - oxide of
trace elements such as titanium.
· After impurities deposited, the liquid is left (with
physical forms such as coffee), is pumped into a series of filters.
Beberpa fine particles of impurities are left pada7
solution will be caught by the filter. This material will be washed
to obtain alumina and caustic soda that can be
reused during the process.
· Already filtered liquid is pumped into the tank six-storytall precipitation. Seed crystals of alumina hydrate (alumina
which binds water molecules) are added on top of the tank. Seed
Crystals will grow in line with the deposition of liquid
and alumina is dissolved will be bound in the crystal
occur.
· The precipitate that formed crystals in the bottom of the tank and then
moved. After washing, transferred to the dryer
for calcining (heating to remove water molecules
molecule bound to the alumina). Temperature range
2000 ° F (1.100 ° C) which will eliminate the water molecules,
so just stay Crystalline anhydrous alumina. Next
cristal flowed into the cooler for cooling and process
finishing.8
The Hall-Heroult process
In general in this process, fused alumina dielektrolisis, where
melt was mixed with the molten electrolyte in the pots kriolit
where the pot is bound by a series of carbon rods at the top
pot as a cathode. Carbon anodes are at the bottom of the pot as
pot lining, with a strong current flow 4-5 V between the anode and katodanya
electrolysis process occurs. Alumina disconnection of bonds due
electrolysis, molten aluminum will go down the pot, which
periodical will be accommodated into a cylindrical mold or
slabs. Each - each pot to produce 66.000 to 110.000 tonnes
aluminum per year (Anonymous, 2009). In general, 4 tons of bauxite will
produce 2 tons of alumina, which will produce 1 ton
aluminum (Ulucak, 2003)
Chemical reactions in general on the Hall-Heroult:
Prose Hall-Heroult By Gradual:
Molten alumina into aluminum metal to occur on steel
vat called a pot reduction. The bottom of the pot is coated / restricted
with carbon which acts as one electrode (conductor
electric current) from the system. Opposite electrode consists of a series of rods
carbon depending on the pot. Pot is structured in such a reduction
appearance, lined consisting of 50-200 pots are connected to one another
form electrical circuits.
• In a pot reduction, the crystals of alumina dissolved in molten
kriolit at temperatures of 1760-1780 ° F (960-970 ° C) so that
resulting electrolyte solution that will deliver listrik9
of carbon rod (Cathode) menujuu-Carbon Layers
(Anode). DC current (4-6 volts and amperes 100000-230000)
melaului flow solution. so that a reaction will occur
will decide aluminum bonding with oxygen on
molecule of alumina. Oxygen is released bound
carbon rod (Cathode), thus forming carbon
dioxide. Pure aluminum deposited at the bottom of the pot as
molten metal.
· Process continued consolidation, with the addition of alumina
the solution to replace compounds kriolit
decomposes. Electric current flows remain constant. Hot
derived from the flow of electricity to keep the contents of pot remain
is in a liquid state. Pure aluminum melt
collected under the pot
· Molten under pots, collected. Accommodated
the mold (rod or plate). When the flow
kecetakan flow, the outer mold is cooled with
water flow, which causes aliminium become solid.
Solid pure metal can be formed by sawing
in accordance with kebutuhan.10
2.3 Use of Aluminium
Some use aluminum, among others:
1. Automotive industry sector, to create truck and component
motor vehicle.
2. to make the fuselage.
3. Housing construction sector; for doors and window frames.
4. Food industry sectors, for packaging various types of products.
5. Other sectors, eg for electric cables, furniture and household
handicrafts.
6. Make thermite, a mixture of aluminum powder with iron powder
(III) oxide, is used to weld steel in place, for example for
connecting railroads. Some Aluminum compounds are also many
use, among others:
1. Tawas (K2SO4.Al2 (SO4) 3.24H2O)
Alum has the chemical formula KSO4.AL2. (SO4) 3.24H2O. Alum
used to purify drinking water in water treatment.
2. Alumina (Al2O3)
Alumina is divided based on alpha-and gamma-allumina allumina. Gammaalumina obtained from heating Al (OH) 3 under 4500C. Gammaalumina used for the manufacture of aluminum, for toothpaste, and
industrial ceramics and glass industries. Obtained from Alfa-allumina
heating Al (OH) 3 at temperatures above 10000C. Alfa-contained allumina
as corundum in nature that are used for sandpaper or Grinding. Stone
noble, such as rubies, sapphires, ametis, and topaz is an alpha-allumina
compounds containing transition metal element that gives color to the stone
them. Ruby colors include:
- Rubi red because they contain compounds of chromium (III)
- Sapphire blue because they contain compounds of iron (II), iron (III) and
titan (IV)
- Ametis violet color because they contain compounds of chromium (III) and
titan (IV)
- Topaz yellow because they contain iron (III) 11
The use of aluminum because aluminum is widely have better properties than other metals such as:
- Lightweight: weighs about 1 / 3 of the weight of iron and steel, or
copper and hence widely used in the transportation industry
such as air transport.
- Strong: especially when combined with other metals. Used
manufacture products that require high strength such as: aircraft
aircraft, ships, pressure vessels, vehicles and others.
- Easy set up with all the metal working process. Easy
assembled because they can be connected to the metal / other material through
welding, brazing, soldering, adhesive bonding, mechanical connections, or
with other grafting techniques.
- Good corrosion resistance: its durabel so well used to
influenced by environmental elements such as water, air, temperature and
Other chemical elements, either in space or even to
seabed.
- Electric conductors: every one kilogram of aluminum can
deliver an electrical current is twice as large when compared with
copper. Because aluminum is relatively inexpensive and lightweight, the aluminum
excellent for overhead electric cables and underground.
- Conductor's hot: This is very good properties for use in machineries / heat transfer equipment so as to provide savings
energy.
- Reflects the light and heat: It can be made in such a way
so having a high reflective capability that is about 95%
compared with the power of reflection of a mirror. This reflective nature
makes aluminum very good for heat radiation shielding equipment.
- Non-magnetic: and therefore very good for use on
electrical / electronics, radio transmitters / TV. and others, where
magnetization factor required negatif.12
- Not toxic: and therefore very good for use on
food industry, beverages, and drugs, namely untuik container and
wrapper.
- Has good toughness: in a cold state and not
such as other metals which become brittle when cooled. This property is
good for use in processing and transportation of LNG where
LNG liquefied gas temperatures can reach below -150 oC.
- Interesting: and therefore aluminum is often used without being
finish the process. Aluminum surface looks very attractive and
therefore suitable for furniture (decoration), building materials and automobiles.
Besides, aluminum can be given a surface treatment, can be glazed,
brushed or painted with various colors, and also given the anodizing process.
This process produces a layer that can also protect the metal from
scratches and other types of abrasion.
- Able to be reprocessed in order that the return process
through the melting process and then formed into products such as
the desired process of re-use can save energy, capital and
valuable raw material.
Metal surface covered by a thin layer of aluminum oxide
protect the metal to air, so the aluminum metal does not react
with air. Aluminum when burned in oxygen will produce
Al2O3 mambentuk white flame.
With a layer of aluminum is often used for coating other metals
so that no corrosion occurs on metal tersebut.13

III.END

3.1Kesimpulan
Aluminum is one of the elements that are very
abundant in nature. Although sangt abundant, not aluminum
never found in pure metallic form, but
always fused with the elements - other elements to form
mineral compounds. Minerals of the most common aluminum
found is bauxite. Where bauaksit contains
aluminum oxide and some trace elements that bind
chemically. To obtain pure aluminum metal from
minerals, required further processing. Processes
most common way to obtain aluminum metal from the mineral
bauxite is through 2 stages of the primary process. That process
Bayer to produce pure aluminum oxide (alumina) from
bauxite. The next process called the Hall-Heroult process by which
the electrolysis process is carried out by modification
thermochemical to produce pure aluminum from alumina.

Aluminum Melting Process

In the smelting process used krusibel kitchen. The material used is a scrap of Al results of research students. The first thing done is the kitchen preparation process. Starting from the melting furnace cleaning and coating with a coating to the placement of coal briquettes in large furnaces.

During the smelting process, material, Al is used to process pre-heating. It aims to eliminate moisture on the surface of the material to avoid gas formation and dissolution in the molten metal that can cause gas defects. After the pre-heating the metal material is inserted into the furnace and allowed to melt. During smelting coal briquettes continuously added to maintain a stable supply of heat to melt metal.

i. Alloying

In the casting process where the addition is intended to produce products that comply with the dimension values are also needed mechanical properties of materials as appropriate. Provision of additional material (alloying) aims to improve the mechanical properties of the material price. For Al granting alloying material using the material of Cu, Zn, Mg, P, Si, Sr, and Na.

In this lab strengthening of alloying is not performed. If it is done and then the samples tested (tensile, hard) then produced a greater value than without alloying.

ii. Degassing

At high temperature hydrogen gas will tend to diffuse into the molten metal. Hydrogen gases must be removed from molten aluminum because it will lead to defects in the body cast. This process is called process gas expenditure degasser. Generally degasser used was in the form of tablets or a gas (argon gas and nitrogen gas).Mechanism of gas expenditure on liquid aluminum metal are as follows:

Tablets are inserted into the molten aluminum will produce gas in the form of a nearly empty air bubbles (<1 atm). Hydrogen gas dissolved in the aluminum can not get out because the pressure inside the molten aluminum <<1 atm while the outside pressure of 1 atm. As a result of air bubbles produced tablets into hydrogen gas and air bubbles are carried upwards bersaman with other impurities dissolved in liquid aluminum. Gas-gas or air bubbles that some will become dross, and will be disposed of through a disposal process dross. In this lab degasser is not used.

iii. Cover Flux

Once the process is complete degasser proceed with the process of flux. The process of flux aims to cover or covering the surface of molten aluminum metal to avoid the entry of hydrogen gas into aluminum metal. Giving flux made at the time began melting aluiminium flux by sprinkling on the surface of liquid aluminum. Covering flux serves for covering the surface of molten metal to avoid the entry of hydrogen gas. Giving flux of this type carried out without stirring. At the lab used flux covering.

Making Aluminum

2011-06-01T14:03:00.000-07:00

Aluminum is a relatively abundant element in the earth's crust. Minerals are a commercial source of aluminum is bauxite. Bauxite contains aluminum in the form of aluminum oxide (Al2O3). Processing of aluminum into pure aluminum can be done through two steps:
1. Bauxite refining stage in order to obtain pure aluminum oxide (alumina)
2. Phase smelting alumina
Bauxite refining stage is to eliminate the major impurities in bauxite. The main impurities of bauxite typically consist of SiO2, Fe2O3, and TiO2. The trick is to dissolve the bauxite in sodium hydroxide (NaOH),
Al2O3 (s) + 2NaOH (aq) + 3H2O (l) ---> 2NaAl (OH) 4 (aq)
Aluminium oxide dissolves in NaOH while pengotornya insoluble. Impurity-impurity can be separated through filtering processes. Furthermore, aluminum was deposited from the filtrate by means of CO2 gas flow and dilution.
2NaAl (OH) 4 (aq) + CO2 (g) ---> 2Al (OH) 3 (s) + Na2CO3 (aq) + H2O (l)
Aluminum hydroxide precipitate is filtered, dried and then heated in order to obtain pure aluminum oxide (Al2O3)
2Al (OH) 3 (s) ---> Al2O3 (s) + 3H2O (g)
Next is the stage by way of reduction smelting alumina through electrolysis process according to Hall-Heroult process.
In the Hall-Heroult, aluminum oxide dissolved in molten kriolit (Na3AlF6) in graphite-coated steel vessel which also functions as a cathode. Further electrolysis carried out at temperature of 950 oC. Graphite rod used as anode.
Source: www.ibchem.com
In the process of electrolysis aluminum produced at the cathode and the anode form O2 and CO2 gas
Al2O3 (l) ---> 2Al3 + (l) + 3O2-(l)

Cathode: Al3 + (l) + 3e ---> Al (l)
Anode: 2O2-(l) ---> O2 (g) + 4 e
C (s) + 2O2-(l) ---> CO2 (g) + 4e

Mercury

2011-05-21T19:25:00.000-07:00

Mercury (element)

From Wikipedia, the free encyclopedia

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gold ← mercury → thallium

Cd
↑
Hg
↓
Cn

80Hg

Periodic table

Appearance

silvery

Spectral lines of Mercury (UV not seen)

General properties

Name, symbol, number

mercury, Hg, 80

Pronunciation

/ˈmɜrkjəri/
or /ˈmɜrkəri/ mer-k(y)ə-ree
alternatively /ˈkwɪksɪlvər/
or /haɪˈdrɑrdʒɪrəm/ hye-drar-ji-rəm

Element category

transition metal

Group, period, block

12, 6, d

Standard atomic weight

200.59

Electron configuration

[Xe] 4f¹⁴ 5d¹⁰ 6s²

Electrons per shell

2, 8, 18, 32, 18, 2 (Image)

Physical properties

Phase

liquid

Liquid density at m.p.

13.534 g·cm⁻³

Melting point

234.32 K, -38.83 °C, -37.89 °F

Boiling point

629.88 K, 356.73 °C, 674.11 °F

Critical point

1750 K, 172.00 MPa

Heat of fusion

2.29 kJ·mol⁻¹

Heat of vaporization

59.11 kJ·mol⁻¹

Specific heat capacity

(25 °C) 27.983 J·mol⁻¹·K⁻¹

Vapor pressure

P (Pa)	1	10	100	1 k	10 k	100 k
at T (K)	315	350	393	449	523	629

Atomic properties

Oxidation states

4, 2 (mercuric), 1 (mercurous)
(mildly basic oxide)

Electronegativity

2.00 (Pauling scale)

Ionization energies

1st: 1007.1 kJ·mol⁻¹

2nd: 1810 kJ·mol⁻¹

3rd: 3300 kJ·mol⁻¹

Atomic radius

151 pm

Covalent radius

132±5 pm

Van der Waals radius

155 pm

Miscellanea

Crystal structure

rhombohedral

Magnetic ordering

diamagnetic

Electrical resistivity

(25 °C) 961nΩ·m

Thermal conductivity

(300 K) 8.30 W·m⁻¹·K⁻¹

Thermal expansion

(25 °C) 60.4 µm·m⁻¹·K⁻¹

Speed of sound

(liquid, 20 °C) 1451.4 m/s

CAS registry number

7439-97-6

Most stable isotopes

Main article: Isotopes of mercury

iso	NA	half-life	DM	DE (MeV)	DP
¹⁹⁴Hg	syn	444 y	ε	0.040	¹⁹⁴Au
¹⁹⁵Hg	syn	9.9 h	ε	1.510	¹⁹⁵Au
¹⁹⁶Hg	0.15%	¹⁹⁶Hg is stable with 116 neutrons
¹⁹⁷Hg	syn	64.14 h	ε	0.600	¹⁹⁷Au
¹⁹⁸Hg	9.97%	¹⁹⁸Hg is stable with 118 neutrons
¹⁹⁹Hg	16.87%	¹⁹⁹Hg is stable with 119 neutrons
²⁰⁰Hg	23.1%	²⁰⁰Hg is stable with 120 neutrons
²⁰¹Hg	13.18%	²⁰¹Hg is stable with 121 neutrons
²⁰²Hg	29.86%	²⁰²Hg is stable with 122 neutrons
²⁰³Hg	syn	46.612 d	β⁻	0.492	²⁰³Tl
²⁰⁴Hg	6.87%	²⁰⁴Hg is stable with 124 neutrons

Mercury ( /ˈmɜrkjəri/ or /ˈmɜrkəri/) is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver ( /ˈkwɪksɪlvər/ ) or hydrargyrum ( /haɪˈdrɑrdʒɪrəm/), from "hydr-" water and "argyros" silver. Mercury is the only metal that is liquid at standard conditions for temperature and pressure; the only other element that is liquid under these conditions is bromine.^[1] With a freezing point of −38.83 °C and boiling point of 356.73 °C, mercury has one of the narrowest ranges of its liquid state of any metal. A heavy, silvery d-block metal, mercury is also one of the five metallic chemical elements that are liquid at or near room temperature and pressure,^[2]^[3] the others being caesium, francium, gallium, and rubidium.

Mercury occurs in deposits throughout the world mostly as cinnabar (mercuric sulfide). The red pigment vermilion is mostly obtained by reduction from cinnabar. Cinnabar is highly toxic by ingestion or inhalation of the dust. Mercury poisoning can also result from exposure to water soluble forms of mercury (such as mercuric chloride or methylmercury), inhalation of mercury vapor, or eating seafood contaminated with mercury.

Mercury is used in thermometers, barometers, manometers, sphygmomanometers, float valves, some electrical switches, and other scientific apparatus, though concerns about the element's toxicity have led to mercury thermometers and sphygmomanometers being largely phased out in clinical environments in favor of alcohol-filled, digital, or thermistor-based instruments. It remains in use in scientific research applications and in amalgam material for dental restoration. It is used in lighting: electricity passed through mercury vapor in a phosphor tube produces short-wave ultraviolet light which then causes the phosphor to fluoresce, making visible light.

Properties

Physical properties

A pound coin (density ~7.6 g/cm³) floats in mercury due to the combination of the buoyant force and surface tension.

Mercury is a heavy, silvery-white metal. As compared to other metals, it is a poor conductor of heat, but a fair conductor of electricity.^[4]

Chemical properties

Mercury has an exceptionally low melting temperature for a d-block metal. A complete explanation of this fact requires a deep excursion into quantum physics, but it can be summarized as follows: mercury has a unique electronic configuration where electrons fill up all the available 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f, 5s, 5p, 5d and 6s subshells. As such configuration strongly resists removal of an electron, mercury behaves similarly to noble gas elements, which form weak bonds and thus easily melting solids. The stability of the 6s shell is due to the presence of a filled 4f shell. An f shell poorly screens the nuclear charge that increases the attractive Coulomb interaction of the 6s shell and the nucleus (see lanthanide contraction). The absence of a filled inner f shell is the reason for the much higher melting temperature of cadmium. Metals such as gold have atoms with one less 6s electron than mercury. Those electrons are more easily removed and are shared between the gold atoms forming relatively strong metallic bonds.^[3]^[5]

At its melting point (−38.86 °C), the density of mercury is^[6] 13.534 g/cm³.

Reactivity and compounds

Mercury and aluminium

Mercury discharge (spectrum) tube

Mercury readily combines with aluminium to form a mercury-aluminium amalgam when the two pure metals come into contact. However, when the amalgam is exposed to air, the aluminium oxidizes, leaving mercury behind. The oxide flakes away, exposing more mercury amalgam, which repeats the process. This process continues until the supply of amalgam is exhausted. Because this process releases mercury, a small amount of mercury can "eat through" a large amount of aluminium over time, by progressively forming amalgam and relinquishing the aluminium as oxide.^[14]

Aluminium in air is ordinarily protected by a molecule-thin layer of its own oxide, which is not porous to oxygen. Mercury coming into contact with the oxide is not detrimental, although if any elemental aluminium is exposed, the mercury may combine with it and potentially damage the aluminium.^[14]^[15] For this reason, restrictions are placed on the use and handling of mercury in proximity with aluminium. In particular, mercury is not allowed aboard an aircraft under most circumstances because of the risk of it forming an amalgam with exposed aluminium parts in the aircraft.^[14]

Isotopes

Main article: Isotopes of mercury

There are seven stable isotopes of mercury with ²⁰²Hg being the most abundant (29.86%). The longest-lived radioisotopes are ¹⁹⁴Hg with a half-life of 444 years, and ²⁰³Hg with a half-life of 46.612 days. Most of the remaining radioisotopes have half-lives that are less than a day. ¹⁹⁹Hg and ²⁰¹Hg are the most often studied NMR-active nuclei, having spins of ¹⁄₂ and ³⁄₂ respectively.^[4]

History

The symbol for the planet Mercury (☿) has been used since ancient times to represent the element

Mercury was found in Egyptian tombs that date from 1500 BC^[16] It was also known to the ancient Chinese.^[17] In China and Tibet, mercury use was thought to prolong life, heal fractures, and maintain generally good health. One of China's emperors, Qín Shǐ Huáng Dì — allegedly buried in a tomb that contained rivers of flowing mercury on a model of the land he ruled, representative of the rivers of China — was killed by drinking a mercury and powdered jade mixture (causing liver failure, poisoning, and brain death) intended to give him eternal life.^[18]^[19] The ancient Greeks used mercury in ointments; the ancient Egyptians and the Romans used it in cosmetics which sometimes deformed the face. By 500 BC mercury was used to make amalgams (Medieval Latin amalgama, "alloy of mercury") with other metals.^[20] The Indian word for alchemy is Rasavātam which means "the way of mercury".^[21]

Alchemists thought of mercury as the First Matter from which all metals were formed. They believed that different metals could be produced by varying the quality and quantity of sulfur contained within the mercury. The purest of these was gold, and mercury was called for in attempts at the transmutation of base (or impure) metals into gold, which was the goal of many alchemists.^[22]

Hg is the modern chemical symbol for mercury. It comes from hydrargyrum, a Latinized form of the Greek word Ύδραργυρος (hydrargyros), which is a compound word meaning "water-silver" (hydr- = water, argyros = silver) — since it is liquid like water and shiny like silver. The element was named after the Roman god Mercury, known for speed and mobility. It is associated with the planet Mercury; the astrological symbol for the planet is also one of the alchemical symbols for the metal. Mercury is the only metal for which the alchemical planetary name became the common name.^[22]

The mines in Almadén (Spain), Monte Amiata (Italy), and Idrija (now Slovenia) dominated the mercury production from the opening of the mine in Almadén 2500 years ago until new deposits were found at the end of the 19th century.^[23]

Occurrence

Mercury output in 2005

Mercury is an extremely rare element in the Earth's crust, having an average crustal abundance by mass of only 0.08 parts per million (ppm).^[24] However, because it does not blend geochemically with those elements that constitute the majority of the crustal mass, mercury ores can be extraordinarily concentrated considering the element's abundance in ordinary rock. The richest mercury ores contain up to 2.5% mercury by mass, and even the leanest concentrated deposits are at least 0.1% mercury (12,000 times average crustal abundance). It is found either as a native metal (rare) or in cinnabar, corderoite, livingstonite and other minerals, with cinnabar (HgS) being the most common ore.^[25] Mercury ores usually occur in very young orogenic belts where rock of high density are forced to the crust of the Earth, often in hot springs or other volcanic regions.^[26]

Beginning in 1558, with the invention of the patio process to extract silver from ore using mercury, mercury became an essential resource in the economy of Spain and its American colonies. Mercury was used to extract silver from the lucrative mines in New Spain and Peru. Initially, the Spanish Crown's mines in Almaden in Southern Spain supplied all the mercury for the colonies.^[27] Mercury deposits were discovered in the New World, and more than 100,000 tons of mercury were mined from the region of Huancavelica, Peru, over the course of three centuries following the discovery of deposits there in 1563. The patio process and later pan amalgamation process continued to create great demand for mercury to treat silver ores until the late 19th century.^[28]

Native mercury with cinnabar, Socrates mine, Sonoma County, California. Cinnabar sometimes alters to native mercury in the oxidized zone of mercury deposits.

Former mines in Italy, the United States and Mexico which once produced a large proportion of the world supply have now been completely mined out or, in the case of Slovenia (Idrija) and Spain (Almadén), shut down due to the fall of the price of mercury. Nevada's McDermitt Mine, the last mercury mine in the United States, closed in 1992. The price of mercury has been highly volatile over the years and in 2006 was $650 per 76-pound (34.46 kg) flask.^[29]

Mercury is extracted by heating cinnabar in a current of air and condensing the vapor. The equation for this extraction is

HgS + O₂ → Hg + SO₂

In 2005, China was the top producer of mercury with almost two-thirds global share followed by Kyrgyzstan.^[30] Several other countries are believed to have unrecorded production of mercury from copper electrowinning processes and by recovery from effluents.

Because of the high toxicity of mercury, both the mining of cinnabar and refining for mercury are hazardous and historic causes of mercury poisoning. In China, prison labor was used by a private mining company as recently as the 1950s to create new cinnabar mercury mines. Thousands of prisoners were used by the Luo Xi mining company to establish new tunnels.^[31] In addition, worker health in functioning mines is at high risk.

The European Union directive calling for compact fluorescent bulbs to be made mandatory by 2012 has encouraged China to re-open deadly cinnabar mines to obtain the mercury required for CFL bulb manufacture. As a result, environmental dangers have been a concern, particularly in the southern cities of Foshan and Guangzhou, and in the Guizhou province in the south west.^[31]

Abandoned mercury mine processing sites often contain very hazardous waste piles of roasted cinnabar calcines. Water run-off from such sites is a recognized source of ecological damage. Former mercury mines may be suited for constructive re-use. For example, in 1976 Santa Clara County, California purchased the historic Almaden Quicksilver Mine and created a county park on the site, after conducting extensive safety and environmental analysis of the property.^[32]

Releases in the environment

Amount of atmospheric mercury deposited at Wyoming's Upper Fremont Glacier over the last 270 years

Preindustrial deposition rates of mercury from the atmosphere may be about 4 ng /(1 L of ice deposit). Although that can be considered a natural level of exposure, regional or global sources have significant effects. Volcanic eruptions can increase the atmospheric source by 4–6 times.^[33]

Natural sources, such as volcanoes, are responsible for approximately half of atmospheric mercury emissions. The human-generated half can be divided into the following estimated percentages:^[34]^[35]^[36]

65% from stationary combustion, of which coal-fired power plants are the largest aggregate source (40% of U.S. mercury emissions in 1999). This includes power plants fueled with gas where the mercury has not been removed. Emissions from coal combustion are between one and two orders of magnitude higher than emissions from oil combustion, depending on the country.^[34]
11% from gold production. The three largest point sources for mercury emissions in the U.S. are the three largest gold mines. Hydrogeochemical release of mercury from gold-mine tailings has been accounted as a significant source of atmospheric mercury in eastern Canada.^[37]
6.8% from non-ferrous metal production, typically smelters.
6.4% from cement production.
3.0% from waste disposal, including municipal and hazardous waste, crematoria, and sewage sludge incineration. This is a significant underestimate due to limited information, and is likely to be off by a factor of two to five.
3.0% from caustic soda production.
1.4% from pig iron and steel production.
1.1% from mercury production, mainly for batteries.
2.0% from other sources.

The above percentages are estimates of the global human-caused mercury emissions in 2000, excluding biomass burning, an important source in some regions.^[34]

Current atmospheric mercury contamination in outdoor urban air is (0.01–0.02 µg/m³) indoor concentrations are significantly elevated over outdoor concentrations, in the range 0.0065–0.523 µg/m³ (average 0.069 µg/m³).^[38]

Mercury also enters into the environment through the improper disposal (e.g., land filling, incineration) of certain products. Products containing mercury include: auto parts, batteries, fluorescent bulbs, medical products, thermometers, and thermostats.^[39] Due to health concerns (see below), toxics use reduction efforts are cutting back or eliminating mercury in such products. For example, most thermometers now use pigmented alcohol instead of mercury. Mercury thermometers are still occasionally used in the medical field because they are more accurate than alcohol thermometers, though both are being replaced by electronic thermometers. Mercury thermometers are still widely used for certain scientific applications because of their greater accuracy and working range.

The United States Clean Air Act, passed in 1990, put mercury on a list of toxic pollutants that need to be controlled to the greatest possible extent. Thus, industries that release high concentrations of mercury into the environment agreed to install maximum achievable control technologies (MACT). In March 2005 EPA rule^[40] added power plants to the list of sources that should be controlled and a national cap and trade rule was issued. States were given until November 2006 to impose stricter controls, and several States are doing so. The rule was being subjected to legal challenges from several States in 2005 and decision was made in 2008. The Clean Air Mercury Rule was struck down by a Federal Appeals Court on February 8, 2008. The rule was deemed not sufficient to protect the health of persons living near coal-fired power plants. The court opinion cited the negative impact on human health from coal fired power plants' mercury emissions documented in the EPA Study Report to Congress of 1998.^[41]

Historically, one of the largest releases was from the Colex plant, a lithium-isotope separation plant at Oak Ridge. The plant operated in the 1950s and 1960s. Records are incomplete and unclear, but government commissions have estimated that some two million pounds of mercury are unaccounted for.^[42]

One of the worst industrial disasters in history was caused by the dumping of mercury compounds into Minamata Bay, Japan. The Chisso Corporation, a fertilizer and later petrochemical company, was found responsible for polluting the bay from 1932–1968. It is estimated that over 3,000 people suffered various deformities, severe mercury poisoning symptoms or death from what became known as Minamata disease.^[43]

Applications

The bulb of a mercury-in-glass thermometer

Mercury is used primarily for the manufacture of industrial chemicals or for electrical and electronic applications. It is used in some thermometers, especially ones which are used to measure high temperatures. A still increasing amount is used as gaseous mercury in fluorescent lamps, while most of the other applications are slowly phased out due to health and safety regulations and is in some applications replaced with less toxic but considerably more expensive Galinstan alloy.

Present use

Medicine

Amalgam filling

The deep violet glow of a mercury vapor discharge in a germicidal lamp, whose spectrum is rich in invisible ultraviolet radiation.

Cosmetics

Mercury, as thiomersal, is widely used in the manufacture of mascara. In 2008, Minnesota became the first state in the US to ban intentionally added mercury in cosmetics, giving it a tougher standard than the federal government.^[52]

A study in geometric mean urine mercury concentration identified a previously unrecognized source of exposure (skin care products) to inorganic mercury among New York City residents. Population-based biomonitoring also showed that mercury concentration levels are higher in consumers of seafood and fish meals.^[53]

Production of chlorine and caustic soda

Chlorine is produced from sodium chloride (common salt, NaCl) using electrolysis to separate the metallic sodium from the chlorine gas. Usually the salt is dissolved in water to produce a brine. By-products of any such chloralkali process are hydrogen (H₂) and sodium hydroxide (NaOH), which is commonly called caustic soda or lye. By far the largest use of mercury^[54]^[55] in the late 20th century was in the mercury cell process (also called the Castner-Kellner process) where metallic sodium is formed as an amalgam at a cathode made from mercury; this sodium is then reacted with water to produce sodium hydroxide.^[56] Many of the industrial mercury releases of the 20th century came from this process, although modern plants claimed to be safe in this regard.^[55] After about 1985, all new chloralkali production facilities that were built in the United States used either membrane cell or diaphragm cell technologies to produce chlorine.

Gold and silver mining

Historically, mercury was used extensively in hydraulic gold mining in order to help the gold to sink through the flowing water-gravel mixture. Thin mercury particles may form mercury-gold amalgam and therefore increase the gold recovery rates.^[4] Large scale use of mercury stopped in the 1960s. However, mercury is still used in small scale, often clandestine, gold prospecting. It is estimated that 45,000 metric tons of mercury used in California for placer mining have not been recovered.^[57] Mercury was also used in silver mining.^[58]

Other present uses

Skin tanner containing a low-pressure mercury vapor lamp and two infrared lamps, which act both as light source and electrical ballast

Assorted types of fluorescent lamps.

Gaseous mercury is used in mercury-vapor lamps and some "neon sign" type advertising signs and fluorescent lamps. Those low-pressure lamps emit very spectrally narrow lines, which are traditionally used in optical spectroscopy for calibration of spectral position. Commercial calibration lamps are sold for this purpose; however simply reflecting some of the fluorescent-lamp ceiling light into a spectrometer is a common calibration practice.^[59] Gaseous mercury is also found in some electron tubes, including ignitrons, thyratrons, and mercury arc rectifiers.^[60] It is also used in specialist medical care lamps for skin tanning and disinfection (see pictures).^[61] Gaseous mercury is added to cold cathode argon-filled lamps to increase the ionization and electrical conductivity. An argon filled lamp without mercury will have dull spots and will fail to light correctly. Lighting containing mercury can be bombarded/oven pumped only once. When added to neon filled tubes the light produced will be inconsistent red/blue spots until the initial burning-in process is completed; eventually it will light a consistent dull off-blue color.^[62]

Some medical thermometers, especially those for high temperatures, are filled with mercury; however, they are gradually disappearing. In the United States, non-prescription sale of mercury fever thermometers has been banned since 2003.^[63] Mercury is also found in liquid-mirror telescopes. The mirror is formed by rotating liquid mercury on a disk, the parabolic form of the liquid thus formed reflecting and focusing incident light. Such telescopes are cheaper than conventional large mirror telescopes by up to a factor of 100, but the mirror cannot be tilted and always points straight up.^[64]^[65]

Liquid mercury is a part of popular secondary reference electrode (called the calomel electrode) in electrochemistry as an alternative to the standard hydrogen electrode. The calomel electrode is used to work out the electrode potential of half cells.^[66] Last, but not least, the triple point of mercury, −38.8344 °C, is a fixed point used as a temperature standard for the International Temperature Scale (ITS-90).^[4]

Proposed uses

Liquid mercury has been proposed as a working fluid for a heat pipe type of cooling device for spacecraft heat rejection systems or radiation panels.^[67]

Historic uses

Old mercury switches

Mercury manometer to measure pressure

Many historic applications made use of the peculiar physical properties of Mercury, especially as a dense liquid and a liquid metal:

In Islamic Spain, it was used for filling decorative pools. Later, the American artist Alexander Calder built a mercury fountain for the Spanish Pavilion at the 1937 World Exhibition in Paris. The fountain is now on display at the Fundació Joan Miró in Barcelona.^[68]
Mercury was used inside wobbler lures. Its heavy, liquid form made it useful since the lures made an attractive irregular movement when the mercury moved inside the plug. Such use was stopped due to environmental concerns, but illegal preparation of modern fishing plugs has occurred.
The Fresnel lenses of old lighthouses used to float and rotate in a bath of mercury which acted like a bearing.^[69]
Mercury sphygmomanometers (blood pressure meter), barometers, diffusion pumps, coulometers, and many other laboratory instruments. As an opaque liquid with a high density and a nearly linear thermal expansion, it is ideal for this role.^[70]
As an electrically-conductive liquid, it was used in mercury switches (including home mercury light switches installed prior to 1970), tilt switches used in old fire detectors, and tilt switches in many modern home thermostats,^[71]
Due to its acoustic properties, mercury was used as the propagation medium in delay line memory devices used in early digital computers of the mid-20th century.
Experimental mercury vapor turbines were installed to increase the efficiency of fossil-fuel electrical power plants.^[72]The South Meadow power plant in Hartford, CT employed mercury as its working fluid, in a binary configuration with a secondary water circuit, or a number of years starting in the late 1920s in a drive to improve plant efficiency. Several other plants were built, including the Schiller Station in Portsmouth, NH, which went online in 1950. The idea did not catch on industry-wide due to the weight and toxicity of mercury, as well as the advent of supercritical steam plants in later years.^[73]^[74]
Similarly, liquid mercury was used as a coolant for some nuclear reactors; however, sodium is proposed for reactors cooled with liquid metal, because the high density of mercury requires much more energy to circulate as coolant.^[75]
Mercury was a propellant for early ion engines in electric space propulsion systems. Advantages were mercury's high molecular weight, low ionization energy, low dual-ionization energy, high liquid density and liquid storability at room temperature. Disadvantages were concerns regarding environmental impact associated with ground testing and concerns about eventual cooling and condensation of some of the propellant on the spacecraft in long-duration operations. The first spaceflight to use electric propulsion was a mercury-fueled ion thruster developed by NASA Lewis and flown on the Space Electric Rocket Test "SERT-1" spacecraft launched by NASA at its Wallops Flight Facility in 1964. The SERT-1 flight was followed up by the SERT-2 flight in 1970. Mercury and caesium were preferred propellants for ion engines until Hughes Research Laboratory performed studies finding xenon gas to be a suitable replacement. Xenon is now the preferred propellant for ion engines as it has a high molecular weight, little or no reactivity due its noble gas nature, and has a high liquid density under mild cryogenic storage.^[76]^[77]
Mercury has been used to produce liquid mirror telescopes.^[78]

Others applications made use of the chemical properties of mercury:

Mercury was used for preserving wood, developing daguerreotypes, silvering mirrors, anti-fouling paints (discontinued in 1990), herbicides (discontinued in 1995), handheld maze games, cleaning, and road leveling devices in cars. Mercury compounds have been used in antiseptics, laxatives, antidepressants, and in antisyphilitics.
It was allegedly used by allied spies to sabotage German planes: a mercury paste was applied to bare aluminium, causing the metal to rapidly corrode; this would cause structural failures.^[15]
Chloralkali process: The largest industrial use of mercury during the 20th century was in electrolysis for separating chlorine and sodium from brine; mercury being the anode of the Castner-Kellner process. The chlorine was used for bleaching paper (hence the location of many of these plants near paper mills) while the sodium was used to make sodium hydroxide for soaps and other cleaning products. This usage has largely been discontinued, replaced with other technologies that utilize membrane cells.^[79]
As electrodes in some types of electrolysis, batteries (mercury cells), sodium hydroxide and chlorine production, handheld games, catalysts, insecticides.
Mercury was once used as a gun barrel bore cleaner.^[80]^[81]

Hat making

From the mid-18th to the mid-19th centuries, a process called "carroting" was used in the making of felt hats. Animal skins were rinsed in an orange solution (the term "carroting" arose from this color) of the mercury compound mercuric nitrate, Hg(NO₃)₂·2H₂O.^[82] This process separated the fur from the pelt and matted it together. This solution and the vapors it produced were highly toxic. The United States Public Health Service banned the use of mercury in the felt industry in December 1941. The psychological symptoms associated with mercury poisoning are said by some to have inspired the phrase "mad as a hatter". Lewis Carroll's "Mad Hatter" in his book Alice's Adventures in Wonderland was a play on words based on the older phrase, but the character himself does not exhibit symptoms of mercury poisoning.^[83]

Toxicity and safety

Occupational exposure

Due to the health effects of mercury exposure, industrial and commercial uses are regulated in many countries. The World Health Organization, OSHA, and NIOSH all treat mercury as an occupational hazard, and have established specific occupational exposure limits. Environmental releases and disposal of mercury are regulated in the U.S. primarily by the United States Environmental Protection Agency.

Case control studies have shown effects such as tremors, impaired cognitive skills, and sleep disturbance in workers with chronic exposure to mercury vapor even at low concentrations in the range 0.7–42 μg/m³.^[86]^[87] A study has shown that acute exposure (4 – 8 hours) to calculated elemental mercury levels of 1.1 to 44 mg/m³ resulted in chest pain, dyspnea, cough, hemoptysis, impairment of pulmonary function, and evidence of interstitial pneumonitis.^[88] Acute exposure to mercury vapor has been shown to result in profound central nervous system effects, including psychotic reactions characterized by delirium, hallucinations, and suicidal tendency. Occupational exposure has resulted in broad-ranging functional disturbance, including erethism, irritability, excitability, excessive shyness, and insomnia. With continuing exposure, a fine tremor develops and may escalate to violent muscular spasms. Tremor initially involves the hands and later spreads to the eyelids, lips, and tongue. Long-term, low-level exposure has been associated with more subtle symptoms of erethism, including fatigue, irritability, loss of memory, vivid dreams, and depression.^[89]^[90]

Treatment

Research on the treatment of mercury poisoning is limited. Currently available drugs for acute mercurial poisoning include chelators N-acetyl-D, L-penicillamine (NAP), British Anti-Lewisite (BAL), 2,3-dimercapto-1-propanesulfonic acid (DMPS), and dimercaptosuccinic acid (DMSA). In one small study including 11 construction workers exposed to elemental mercury, patients were treated with DMSA and NAP.^[91] Chelation therapy with both drugs resulted in the mobilization of a small fraction of the total estimated body mercury. DMSA was able to increase the excretion of mercury to a greater extent than NAP.^[92]

Fish

Main article: Mercury in fish

Fish and shellfish have a natural tendency to concentrate mercury in their bodies, often in the form of methylmercury, a highly toxic organic compound of mercury. Species of fish that are high on the food chain, such as shark, swordfish, king mackerel, albacore tuna, and tilefish contain higher concentrations of mercury than others. As mercury and methylmercury are fat soluble,^{[verification needed]} they primarily accumulate in the viscera, although they are also found throughout the muscle tissue.^[93] When this fish is consumed by a predator, the mercury level is accumulated. Since fish are less efficient at depurating than accumulating methylmercury, fish-tissue concentrations increase over time. Thus species that are high on the food chain amass body burdens of mercury that can be ten times higher than the species they consume. This process is called biomagnification. Mercury poisoning happened this way in Minamata, Japan, now called Minamata disease.

Regulations

In the United States, the Environmental Protection Agency is charged with regulating and managing mercury contamination. Several laws give the EPA this authority, including the Clean Air Act, the Clean Water Act, the Resource Conservation and Recovery Act, and the Safe Drinking Water Act. Additionally, the Mercury-Containing and Rechargeable Battery Management Act, passed in 1996, phases out the use of mercury in batteries, and provides for the efficient and cost-effective disposal of many types of used batteries.^[94] North America contributed approximately 11% of the total global anthropogenic mercury emissions in 1995.^[95]

In the European Union, the directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment (see RoHS) bans mercury from certain electrical and electronic products, and limits the amount of mercury in other products to less than 1000 ppm.^[96] There are restrictions for mercury concentration in packaging (the limit is 100 ppm for sum of mercury, lead, hexavalent chromium and cadmium) and batteries (the limit is 5 ppm).^[97] In July 2007, the European Union also banned mercury in non-electrical measuring devices, such as thermometers and barometers. The ban applies to new devices only, and contains exemptions for the health care sector and a two year grace period for manufacturers of barometers. ^[98]

Norway enacted a total ban on the use of mercury in the manufacturing and import/export of mercury products, effective January 1, 2008.^[99] In 2002, several lakes in Norway were found to have a poor state of mercury pollution, with an excess of 1 mg/g of mercury in their sediment.^[100]

Platinum

2011-05-21T19:10:00.000-07:00

Platinum

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This article is about the chemical element. For other uses, see Platinum (disambiguation).

iridium ← platinum → gold

Pd
↑
Pt
↓
Ds

78Pt

Periodic table

Appearance

grayish white

General properties

Name, symbol, number

platinum, Pt, 78

Pronunciation

/ˈplæt.n.əm/
or /ˈplæt.nəm/

Element category

transition metal

Group, period, block

10, 6, d

Standard atomic weight

195.084

Electron configuration

[Xe] 4f¹⁴ 5d⁹ 6s¹

Electrons per shell

2, 8, 18, 32, 17, 1 (Image)

Physical properties

Phase

solid

Density (near r.t.)

21.45 g·cm⁻³

Liquid density at m.p.

19.77 g·cm⁻³

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⁻¹

Heat of vaporization

469 kJ·mol⁻¹

Specific heat capacity

(25 °C) 25.86 J·mol⁻¹·K⁻¹

Vapor pressure

P (Pa)	1	10	100	1 k	10 k	100 k
at T (K)	2330	(2550)	2815	3143	3556	4094

Atomic properties

Oxidation states

6, 5, 4, 3 , 2, 1, -1, -2
(mildly basic oxide)

Electronegativity

2.28 (Pauling scale)

Ionization energies

1st: 870 kJ·mol⁻¹

2nd: 1791 kJ·mol⁻¹

Atomic radius

139 pm

Covalent radius

136±5 pm

Van der Waals radius

175 pm

Miscellanea

Crystal structure

face-centered cubic

Magnetic ordering

paramagnetic

Electrical resistivity

(20 °C) 105 nΩ·m

Thermal conductivity

(300 K) 71.6 W·m⁻¹·K⁻¹

Thermal expansion

(25 °C) 8.8 µm·m⁻¹·K⁻¹

125-240 MPa

168 GPa

61 GPa

230 GPa

0.38

4–4.5

549 MPa

392 MPa

7440-06-4

Most stable isotopes

Main article: Isotopes of platinum

iso	NA	half-life	DM	DE (MeV)	DP
¹⁹⁰Pt	0.014%	6.5×10¹¹ y	α	3.18	¹⁸⁶Os
¹⁹²Pt	0.782%	¹⁹²Pt is stable with 114 neutrons
¹⁹³Pt	syn	50 y	ε	?	¹⁹³Ir
¹⁹⁴Pt	32.967%	¹⁹⁴Pt is stable with 116 neutrons
¹⁹⁵Pt	33.832%	¹⁹⁵Pt is stable with 117 neutrons
¹⁹⁶Pt	25.242%	¹⁹⁶Pt is stable with 118 neutrons
¹⁹⁸Pt	7.163%	¹⁹⁸Pt is stable with 120 neutrons

Platinum ( /ˈplæt.n.əm/ or /ˈplæt.nəm/) is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River."^[1] It is a dense, malleable, ductile, precious, gray-white transition metal. Even though it has six naturally occurring isotopes, platinum is one of the rarest elements in the Earth's crust and has an average abundance of approximately 0.005 mg/kg. It occurs in some nickel and copper ores along with some native deposits, mostly in South Africa, which accounts for 80% of the world production.

As a member of the platinum group of elements, as well as of the group 10 of the periodic table of elements, platinum is generally unreactive. It exhibits a remarkable resistance to corrosion, even at high temperatures, and as such is considered a noble metal. As a result, platinum is often found chemically uncombined as native platinum. Because it occurs naturally in the alluvial sands of various rivers, it was first used by pre-Columbian South American natives to produce artifacts. It was referenced in European writings as early as 16th century, but it was not until Antonio de Ulloa published a report on a new metal of Colombian origin in 1748 that it became investigated by scientists.

Platinum is used in catalytic converters, laboratory equipment, electrical contacts and electrodes, platinum resistance thermometers, dentistry equipment, and jewelry. Because only a few hundred tonnes are produced annually, it is a scarce material, and is highly valuable and is a major precious metal commodity. Being a heavy metal, it leads to health issues upon exposure to its salts, but due to its corrosion resistance it is not toxic as a metal. Some of its compounds, most notably cisplatin, are applied in chemotherapy against certain types of cancer.

[edit] Characteristics

[edit] Physical

As a pure metal, platinum is silvery-white, lustrous, ductile, and malleable.^[2] It does not oxidize at any temperature, although it is corroded by halogens, cyanides, sulfur, and caustic alkalis. Platinum is insoluble in hydrochloric and nitric acid, but dissolves in aqua regia to form chloroplatinic acid, H₂PtCl₆.^[3] Platinum's resistance to wear and tarnish is well suited for making fine jewelry. The metal has an excellent resistance to corrosion and high temperature and has stable electrical properties. All of these characteristics have been exploited for industrial applications.^[4]

[edit] Chemical

[edit] Isotopes

Main article: Isotopes of platinum

Platinum has six naturally occurring isotopes: ¹⁹⁰Pt, ¹⁹²Pt, ¹⁹⁴Pt, ¹⁹⁵Pt, ¹⁹⁶Pt, and ¹⁹⁸Pt. The most abundant of these is ¹⁹⁵Pt, comprising 33.83% of all platinum. It is the only stable isotope with a non-zero spin; with a spin of ¹/₂, ¹⁹⁵Pt satellite peaks are often observed in ¹H and ³¹P NMR spectroscopy (i.e. Pt-phosphine and Pt-alkyl complexes). ¹⁹⁰Pt is the least abundant at only 0.01%. Of the naturally occurring isotopes, only ¹⁹⁰Pt is unstable, though it decays with a half-life of 6.5×10¹¹ years. ¹⁹⁸Pt undergoes alpha decay, but because its half-life is estimated at longer than 3.2×10¹⁴ years, it is considered stable. Platinum also has 31 synthetic isotopes ranging in atomic mass from 166 to 202, making the total number of known isotopes 37. The least stable of these is ¹⁶⁶Pt with a half-life of 300 µs, while the most stable is ¹⁹³Pt with a half-life of 50 years. Most platinum isotopes decay by some combination of beta decay and alpha decay. ¹⁸⁸Pt, ¹⁹¹Pt, and ¹⁹³Pt decay primarily by electron capture. ¹⁹⁰Pt and ¹⁹⁸Pt have double beta decay paths.^[7]

[edit] Occurrence

A native platinum nugget, Kondyor mine, Khabarovsk Krai

Platinum output in 2005

Platinum is an extremely rare metal,^[8] occurring at a concentration of only 0.005 ppm in the Earth's crust.^[9]^[10] It is sometimes mistaken for silver (Ag). Platinum is often found chemically uncombined as native platinum and alloyed with iridium as platiniridium. Most often the native platinum is found in secondary deposits; platinum is combined with the other platinum group metals in alluvial deposits. The alluvial deposits used by pre-Columbian people in the Chocó Department, Colombia are still a source for platinum group metals. Another large alluvial deposit is in the Ural Mountains, Russia, and it is still mined.^[3]

In nickel and copper deposits, platinum group metals occur as sulfides (e.g., (Pt,Pd)S), tellurides (e.g., PtBiTe), antimonides (PdSb), and arsenides (e.g., PtAs₂), and as end alloys with nickel or copper. Platinum arsenide, sperrylite (PtAs₂), is a major source of platinum associated with nickel ores in the Sudbury Basin deposit in Ontario, Canada. At Platinum, Alaska, about 545,000 troy ounces had been mined between 1927 and 1975. The mine ceased operations in 1990.^[11] 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, Gauteng, South Africa.^[12]

In 1865, chromites were identified in the Bushveld region of South Africa, followed by the discovery of platinum in 1906.^[13] The largest known primary reserves are in the Bushveld complex in South Africa.^[14] The large copper–nickel deposits near Norilsk in Russia, and the Sudbury Basin, Canada, are the two other large deposits. In the Sudbury Basin, the huge quantities of nickel ore processed make up for the fact platinum is present as only 0.5 ppm in the ore. Smaller reserves can be found in the United States,^[14] for example in the Absaroka Range in Montana.^[15] In 2009, South Africa was the top producer of platinum, with an almost 80% share, followed by Russia at 11%.^[16]

Platinum exists in higher abundances on the Moon and in meteorites. Correspondingly, platinum is found in slightly higher abundances at sites of bolide impact on the Earth that are associated with resulting post-impact volcanism, and can be mined economically; the Sudbury Basin is one such example.^[17]

[edit] Compounds

[edit] Halides

Hexachloroplatinic acid mentioned above is probably the most important platinum compound, as it serves as the precursor for many other platinum compounds. By itself, it has various applications in photography, zinc etchings, indelible ink, plating, mirrors, porcelain coloring, and as a catalyst.^[18]

Treatment of hexachloroplatinic acid with an ammonium salt, such as ammonium chloride, gives ammonium hexachloroplatinate,^[5] which is relatively insoluble in ammonium solutions. Heating this ammonium salt in the presence of hydrogen reduces it to elemental platinum. Potassium hexachloroplatinate is similarly insoluble, and hexachloroplatinic acid has been used in the determination of potassium ions by gravimetry.^[19]

When hexachloroplatinic acid is heated, it decomposes through platinum(IV) chloride and platinum(II) chloride to elemental platinum, although the reactions do not occur stepwise:^[20]

(H₃O)₂PtCl₆·nH₂O PtCl₄ + 2 HCl + (n + 2) H₂O

PtCl₄ PtCl₂ + Cl₂

PtCl₂ Pt + Cl₂

All three reactions are reversible. Platinum(II) and platinum(IV) bromides are known as well. Platinum hexafluoride is a strong oxidizer capable of oxidizing oxygen.

[edit] Oxides

Platinum(IV) oxide, PtO₂, also known as Adams' catalyst, is a black powder which is soluble in KOH solutions and concentrated acids.^[21] PtO₂ and the less common PtO both decompose upon heating.^[2] Platinum(II,IV) oxide, Pt₃O₄, is formed in the following reaction:

2 Pt²⁺ + Pt⁴⁺ + 4 O²⁻ → Pt₃O₄

Platinum also forms a trioxide, where it is present in the +4 oxidation state.

[edit] Other compounds

Unlike palladium acetate, platinum(II) acetate is not commercially available. Where a base is desired, the halides have been used in conjunction with sodium acetate.^[6] The use of platinum(II) acetylacetonate has also been reported.^[22]

Several barium platinides have been synthesized in which platinum exhibits negative oxidation states ranging from −1 to −2. These include BaPt, Ba₃Pt₂, and Ba₂Pt.^[23] Caesium platinide, Cs₂Pt, has been shown to contain Pt2−
anions.^[24] Platinum also exhibits negative oxidation states at surfaces reduced electrochemically.^[25] The negative oxidation states exhibited by platinum are unusual for metallic elements, and they are attributed to the relativistic stabilization of the 6s orbitals.^[24]

Zeise's salt, containing an ethylene ligand, was one of the first organometallic compounds discovered. Dichloro(cycloocta-1,5-diene)platinum(II) is a commercially available olefin complex, which contains easily displaceable cod ligands ("cod" being an abbreviation of 1,5-cyclooctadiene). The cod complex and the halides are convenient starting points to platinum chemistry.^[6]

Cisplatin, or cis-diamminedichloroplatinum(II) is the first of a series of square planar platinum(II)-containing chemotherapy drugs, including carboplatin and oxaliplatin. These compounds are capable of crosslinking DNA, and kill cells by similar pathways to alkylating chemotherapeutic agents.^[26]

The hexachloroplatinate ion
The anion of Zeise's salt
Dichloro(cycloocta-1,5-diene)platinum(II)
Cisplatin

[edit] History

Platinum occurs naturally in the alluvial sands of various rivers, though there is little evidence of its use by ancient people. However, the metal was used by pre-Columbian Americans near modern-day Esmeraldas, Ecuador to produce artifacts of a white gold-platinum alloy. The first European reference to platinum appears in 1557 in the writings of the Italian humanist Julius Caesar Scaliger as a description of an unknown noble metal found between Darién and Mexico, "which no fire nor any Spanish artifice has yet been able to liquefy."^[27]

This alchemical symbol for platinum was made by joining the symbols of silver and gold.

Antonio de Ulloa is credited with the discovery of platinum.

In 1741, Charles Wood, a British metallurgist, found various samples of Colombian platinum in Jamaica, which he sent to William Brownrigg for further investigation. Antonio de Ulloa, also credited with the discovery of platinum, returned to Spain from the French Geodesic Mission in 1746 after having been there for eight years. His historical account of the expedition included a description of platinum as being neither separable nor 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.^[27]

In 1750, after studying the platinum sent to him by Wood, Brownrigg presented a detailed account of the metal to the Royal Society, mentioning that he had seen no mention of it in any previous accounts of known minerals. Brownrigg also made note of platinum's extremely high melting point and refractoriness toward borax. Other chemists across Europe soon began studying platinum, including Torbern Bergman, Jöns Jakob Berzelius, William Lewis, and Pierre Macquer. In 1752, 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.^[27]

Carl von Sickingen researched platinum extensively in 1772. He succeeded in making malleable platinum by alloying it with gold, dissolving the alloy in 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 volatilizing the arsenic.^[27]

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 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.^[27]

In 2007, Gerhard Ertl won the Nobel Prize in Chemistry for determining the detailed molecular mechanisms of the catalytic oxidation of carbon monoxide over platinum (catalytic converter).^[28]

[edit] Production

1,000 cubic centimeters of 99.9% pure platinum, worth about US$910,000 at 30 October 2009 prices

Platinum, along with the rest of the platinum metals is, obtained commercially as a by-product from nickel and copper mining and processing. During electrorefining of copper, noble metals, such as silver, gold and the platinum group metals, as well as selenium and tellurium, settle to the bottom of the cell as "anode mud", which forms the starting point for the extraction of the platinum group metals.^[29]^[30]

If pure platinum is found in placer deposits or other ores, it is isolated from them by various methods of subtracting impurities. Because platinum is significantly denser than many of its impurities, the lighter impurities can be removed by simply floating them away in a liquid. Platinum is also nonmagnetic, while nickel and iron are both magnetic. These two impurities are thus removed by running an electromagnet over the mixture. Because platinum has a higher melting point than most other substances, many impurities can be burned or melted away without melting the platinum. Finally, platinum is resistant to hydrochloric and sulfuric acids, while other substances are readily attacked by them. Metal impurities can be removed by stirring the mixture in either of the two acids and recovering the remaining platinum.^[31]

One suitable method for purification for the raw platinum, which contains platinum, gold, and the other platinum group metals, is to process it with aqua regia, in which palladium, gold and platinum are dissolved, while osmium, iridium, ruthenium and rhodium stay unreacted. The gold is precipitated by the addition of iron(III) chloride and after filtering off the gold, the platinum is precipitated by the addition of ammonium chloride as ammonium chloroplatinate. Ammonium chloroplatinate can be converted to the metal by heating.^[32]

[edit] Applications

Cross section of a metal-core catalytic converter

Of the 239 tonnes of platinum sold in 2006, 130 tonnes were used for vehicle emissions control devices, 49 tonnes for jewelry, 13.3 tonnes in electronics, and 11.2 tonnes in the chemical industry as a catalyst. The remaining 35.5 tonnes went to various other minor applications, such as electrodes, anticancer drugs, oxygen sensors, spark plugs and turbine engines.^[33]

[edit] Catalysis

The most common use of platinum is as a catalyst in chemical reactions, many times as platinum black. It has been employed in this application since the early 19th century, when platinum powder was used to catalyze the ignition of hydrogen. Its most important application is in automobiles as a catalytic converter, which allows the complete combustion of low concentrations of unburned hydrocarbons from the exhaust into carbon dioxide and water vapor. Platinum is also used in the petroleum industry as a catalyst in a number of separate processes, but especially in catalytic reforming of straight run naphthas into higher-octane gasoline which becomes rich in aromatic compounds. PtO₂, also known as Adams' catalyst, is used as a hydrogenation catalyst, specifically for vegetable oils.^[18] Platinum metal also strongly catalyzes the decomposition of hydrogen peroxide into water and oxygen gas.^[34]

[edit] Standard

International Prototype Meter bar

From 1889 to 1960, the meter was defined as the length of a platinum-iridium (90:10) alloy bar, known as the International Prototype Meter bar. The previous bar was made of platinum in 1799. The International Prototype Kilogram remains defined by a cylinder of the same platinum-iridium alloy made in 1879.^[35]

The standard hydrogen electrode also uses a platinized platinum electrode due to its corrosion resistance, and other attributes.^[36]

[edit] Precious metal

Platinum Eagle

Main articles: Platinum as an investment and Platinum coin

Platinum is a precious metal commodity; its bullion has the ISO currency code of XPT. Coins, bars, and ingots are traded or collected. Platinum finds use in jewelry, usually as a 90–95% alloy, due to its inertness and shine. In watchmaking, Vacheron Constantin, Patek Philippe, Rolex, Breitling, and other companies use platinum for producing their limited edition watch series. Watchmakers appreciate the unique properties of platinum, as it neither tarnishes nor wears out (relative to gold).^[37]

Average price of platinum from 1991 to 2007 in US$ per troy ounce (~$20/g)^[38]

The price of platinum, like other industrial commodities, is more volatile than that of gold. In 2008, the price of platinum ranged from $774 to $2,252 per oz.^[39]

During periods of sustained economic stability and growth, the price of platinum tends to be as much as twice the price of gold, whereas during periods of economic uncertainty,^[40] the price of platinum tends to decrease due to reduced industrial demand, falling below the price of gold. Gold prices are more stable in slow economic times, as gold is considered a safe haven and gold demand is not driven by industrial uses. In the 18th century, platinum's rarity made King Louis XV of France declare it the only metal fit for a king.^[41]

[edit] Other uses

In the laboratory, platinum wire is used for electrodes; platinum pans and supports are used in thermogravimetric analysis because of the stringent requirements of chemical inertness upon heating to high temperatures (~1000°C). Platinum is used as an alloying agent for various metal products, including fine wires, noncorrosive laboratory containers, medical instruments, dental prostheses, electrical contacts, and thermocouples. Platinum-cobalt, an alloy of roughly three parts platinum and one part cobalt, is used to make relatively strong permanent magnets.^[18] Platinum-based anodes are used in ships, pipelines, and steel piers.^[3]

[edit] Symbol of prestige

See also: Platinum album and Platinum (color)

An assortment of native platinum nuggets

Platinum's rarity as a metal has caused advertisers to associate it with exclusivity and wealth. "Platinum" debit cards have greater privileges than do "gold" ones.^[42] "Platinum awards" are the second highest possible, ranking above "gold", "silver" and "bronze", but below diamond. For example, in the United States, a musical album that has sold more than 1 million copies, will be credited as "platinum", whereas an album that sold more than 10 million copies will be certified as “diamond”.^[43] Some products, such as blenders and vehicles, with a silvery-white color are identified as "platinum". Platinum is considered a precious metal, although its use is not as common as 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 this particular metal.^[44]

[edit] Health issues

According to the Centers for Disease Control and Prevention, short-term exposure to platinum salts may cause irritation of the eyes, nose, and throat, and long-term exposure may cause both respiratory and skin allergies. The current OSHA standard is 2 micrograms per cubic meter of air averaged over an 8-hour work shift.^[45]

Certain platinum complexes are used in chemotherapy, and show good activity against some tumors. Cisplatin is particularly effective against testicular cancer; the cure rate was improved from 10% to 85%.^[46] However, the side effects are severe. Cisplatin causes cumulative, irreversible kidney damage and deafness.^[47] As with other ototoxic agents, deafness may be secondary to interactions with melanin in the stria vascularis.

As platinum is a catalyst in the manufacture of the silicone rubber and gel components of several types of medical implants (breast implants, joint replacement prosthetics, artificial lumbar discs, vascular access ports, etc.), the possibility platinum could enter the body and cause adverse effects has merited study. The Food and Drug Administration and other institutions have reviewed the issue and found no evidence to suggest toxicity in vivo.^[48]^[49]

metals description

Aluminium

Making Aluminum

Mercury

Mercury (element)

Contents

Properties

Physical properties

Chemical properties

Reactivity and compounds

Mercury and aluminium

Isotopes

History

Occurrence

Releases in the environment

Applications

Present use

Medicine

Cosmetics

Production of chlorine and caustic soda

Gold and silver mining

Other present uses

Proposed uses

Historic uses

Hat making

Toxicity and safety

Occupational exposure

Treatment

Fish

Regulations

Platinum

Platinum

Contents

[edit] Characteristics

[edit] Physical

[edit] Chemical

[edit] Isotopes

[edit] Occurrence

[edit] Compounds

[edit] Halides

[edit] Oxides

[edit] Other compounds

[edit] History

[edit] Production

[edit] Applications

[edit] Catalysis

[edit] Standard

[edit] Precious metal

[edit] Other uses

[edit] Symbol of prestige

[edit] Health issues