Zinc is a
chemical element
A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler sub ...
with the
symbol
A symbol is a mark, sign, or word that indicates, signifies, or is understood as representing an idea, object, or relationship. Symbols allow people to go beyond what is known or seen by creating linkages between otherwise very different conc ...
Zn and atomic number 30. Zinc is a slightly brittle metal at
room temperature
Colloquially, "room temperature" is a range of air temperatures that most people prefer for indoor settings. It feels comfortable to a person when they are wearing typical indoor clothing. Human comfort can extend beyond this range depending on ...
and has a shiny-greyish appearance when oxidation is removed. It is the first element in
group 12 (IIB) of the
periodic table
The periodic table, also known as the periodic table of the (chemical) elements, is a rows and columns arrangement of the chemical elements. It is widely used in chemistry, physics, and other sciences, and is generally seen as an icon of ch ...
. In some respects, zinc is chemically similar to
magnesium
Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
: both elements exhibit only one normal oxidation state (+2), and the Zn
2+ and Mg
2+ ion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...
s are of similar size.
[The elements are from different metal groups. See periodic table.] Zinc is the 24th most abundant
element in Earth's crust and has five stable
isotope
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...
s. The most common zinc
ore
Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 Apr ...
is
sphalerite
Sphalerite (sometimes spelled sphaelerite) is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in Sedimentary exhalative deposits, sedimen ...
(zinc blende), a
zinc sulfide
Zinc sulfide (or zinc sulphide) is an inorganic compound with the chemical formula of ZnS. This is the main form of zinc found in nature, where it mainly occurs as the mineral sphalerite. Although this mineral is usually black because of various ...
mineral. The largest workable
lode
In geology, a lode is a deposit of metalliferous ore that fills or is embedded in a fissure (or crack) in a rock formation or a vein of ore that is deposited or embedded between layers of rock.
The current meaning (ore vein) dates from the 17t ...
s are in Australia, Asia, and the United States. Zinc is refined by
froth flotation
Froth flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is used in mineral processing, paper recycling and waste-water treatment industries. Historically this was first used in the mining industry, wher ...
of the ore,
roasting
Roasting is a cooking method that uses dry heat where hot air covers the food, cooking it evenly on all sides with temperatures of at least from an open flame, oven, or other heat source. Roasting can enhance the flavor through caramelization ...
, and final
extraction using
electricity
Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described ...
(
electrowinning).
Zinc is an essential
trace element
__NOTOC__
A trace element, also called minor element, is a chemical element whose concentration (or other measure of amount) is very low (a "trace amount"). They are classified into two groups: essential and non-essential. Essential trace elements ...
for humans,
animals,
plants
and for
microorganism
A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
s
and is necessary for prenatal and postnatal development.
It is the second most abundant trace metal in humans after iron and it is the only metal which appears in all
enzyme classes.
Zinc is also an essential nutrient element for coral growth as it is an important cofactor for many enzymes.
Zinc deficiency
Zinc deficiency is defined either as insufficient zinc to meet the needs of the body, or as a serum zinc level below the normal range. However, since a decrease in the serum concentration is only detectable after long-term or severe depletion, s ...
affects about two billion people in the developing world and is associated with many diseases.
In children, deficiency causes growth retardation, delayed sexual maturation, infection susceptibility, and
diarrhea
Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin wi ...
.
Enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
s with a zinc atom in the
reactive center
A reactive center, also called a propagating center, in chemistry is a particular location, usually an atom, within a chemical compound that is the likely center of a reaction in which the chemical is involved. In chain-growth polymer chemistry thi ...
are widespread in biochemistry, such as
alcohol dehydrogenase
Alcohol dehydrogenases (ADH) () are a group of dehydrogenase enzymes that occur in many organisms and facilitate the interconversion between alcohols and aldehydes or ketones with the reduction of nicotinamide adenine dinucleotide (NAD+) to N ...
in humans. Consumption of excess zinc may cause
ataxia
Ataxia is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and abnormalities in eye movements. Ataxia is a clinical manifestation indicating dysfunction of ...
,
lethargy
Lethargy is a state of tiredness, sleepiness, weariness, fatigue, sluggishness or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to inadequate sleep, overexertion, overwo ...
, and
copper deficiency
Copper deficiency, or hypocupremia, is defined either as insufficient copper to meet the needs of the body, or as a serum copper level below the normal range. Symptoms may include fatigue, decreased red blood cells, early greying of the hair, an ...
.
Brass
Brass is an alloy of copper (Cu) and zinc (Zn), in proportions which can be varied to achieve different mechanical, electrical, and chemical properties. It is a substitutional alloy: atoms of the two constituents may replace each other with ...
, an
alloy
An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...
of
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
and zinc in various proportions, was used as early as the third millennium BC in the
Aegean area and the region which currently includes
Iraq
Iraq,; ku, عێراق, translit=Êraq officially the Republic of Iraq, '; ku, کۆماری عێراق, translit=Komarî Êraq is a country in Western Asia. It is bordered by Turkey to Iraq–Turkey border, the north, Iran to Iran–Iraq ...
, the
United Arab Emirates
The United Arab Emirates (UAE; ar, اَلْإِمَارَات الْعَرَبِيَة الْمُتَحِدَة ), or simply the Emirates ( ar, الِْإمَارَات ), is a country in Western Asia (The Middle East). It is located at th ...
,
Kalmykia
he official languages of the Republic of Kalmykia are the Kalmyk and Russian languages./ref>
, official_lang_list= Kalmyk
, official_lang_ref=Steppe Code (Constitution) of the Republic of Kalmykia, Article 17: he official languages of the ...
,
Turkmenistan
Turkmenistan ( or ; tk, Türkmenistan / Түркменистан, ) is a country located in Central Asia, bordered by Kazakhstan to the northwest, Uzbekistan to the north, east and northeast, Afghanistan to the southeast, Iran to the sout ...
and
Georgia
Georgia most commonly refers to:
* Georgia (country), a country in the Caucasus region of Eurasia
* Georgia (U.S. state), a state in the Southeast United States
Georgia may also refer to:
Places
Historical states and entities
* Related to the ...
. In the second millennium BC it was used in the regions currently including
West India
Western India is a loosely defined region of India consisting of its western part. The Ministry of Home Affairs in its Western Zonal Council Administrative division includes the states of Goa, Gujarat, and Maharashtra along with the Unio ...
,
Uzbekistan
Uzbekistan (, ; uz, Ozbekiston, italic=yes / , ; russian: Узбекистан), officially the Republic of Uzbekistan ( uz, Ozbekiston Respublikasi, italic=yes / ; russian: Республика Узбекистан), is a doubly landlocked cou ...
,
Iran
Iran, officially the Islamic Republic of Iran, and also called Persia, is a country located in Western Asia. It is bordered by Iraq and Turkey to the west, by Azerbaijan and Armenia to the northwest, by the Caspian Sea and Turkmeni ...
,
Syria
Syria ( ar, سُورِيَا or سُورِيَة, translit=Sūriyā), officially the Syrian Arab Republic ( ar, الجمهورية العربية السورية, al-Jumhūrīyah al-ʻArabīyah as-Sūrīyah), is a Western Asian country loc ...
, Iraq, and
Israel
Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...
.
Zinc
metal
A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...
was not produced on a large scale until the 12th century in India, though it was known to the ancient Romans and Greeks. The mines of
Rajasthan
Rajasthan (; lit. 'Land of Kings') is a state in northern India. It covers or 10.4 per cent of India's total geographical area. It is the largest Indian state by area and the seventh largest by population. It is on India's northwestern si ...
have given definite evidence of zinc production going back to the 6th century BC. To date, the oldest evidence of pure zinc comes from Zawar, in Rajasthan, as early as the 9th century AD when a distillation process was employed to make pure zinc.
Alchemists
Alchemy (from Arabic: ''al-kīmiyā''; from Ancient Greek: χυμεία, ''khumeía'') is an ancient branch of natural philosophy, a philosophical and protoscientific tradition that was historically practiced in China, India, the Muslim world, ...
burned zinc in air to form what they called "
philosopher's wool" or "white snow".
The element was probably named by the alchemist
Paracelsus after the German word ''Zinke'' (prong, tooth). German chemist
Andreas Sigismund Marggraf
Andreas Sigismund Marggraf (; 3 March 1709 – 7 August 1782) was a German chemist from Berlin, then capital of the Margraviate of Brandenburg, and a pioneer of analytical chemistry. He isolated zinc in 1746 by heating Calamine (mineral), calamine ...
is credited with discovering pure metallic zinc in 1746. Work by
Luigi Galvani and
Alessandro Volta
Alessandro Giuseppe Antonio Anastasio Volta (, ; 18 February 1745 – 5 March 1827) was an Italian physicist, chemist and lay Catholic who was a pioneer of electricity and power who is credited as the inventor of the electric battery and the ...
uncovered the electrochemical properties of zinc by 1800.
Corrosion
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...
-resistant
zinc plating
Galvanization or galvanizing ( also spelled galvanisation or galvanising) is the process of applying a protective zinc coating to steel or iron, to prevent rusting. The most common method is hot-dip galvanizing, in which the parts are submerg ...
of iron (
hot-dip galvanizing
Hot-dip galvanization is a form of galvanization. It is the process of coating iron and steel with zinc, which alloys with the surface of the base metal when immersing the metal in a bath of molten zinc at a temperature of around . When expose ...
) is the major application for zinc. Other applications are in electrical
batteries, small non-structural castings, and alloys such as brass. A variety of zinc compounds are commonly used, such as
zinc carbonate
Zinc carbonate is the inorganic compound with the formula ZnCO3. It is a white solid that is insoluble in water. It exists in nature as the mineral smithsonite. It is prepared by treating cold solutions of zinc sulfate with potassium bicarbonat ...
and
zinc gluconate
Zinc gluconate is the zinc salt of gluconic acid. It is an ionic compound consisting of two anions of gluconate for each zinc(II) cation. Zinc gluconate is a popular form for the delivery of zinc as a dietary supplement providing 14.35% eleme ...
(as dietary supplements),
zinc chloride
Zinc chloride is the name of inorganic chemical compounds with the formula ZnCl2 and its hydrates. Zinc chlorides, of which nine crystalline forms are known, are colorless or white, and are highly soluble in water. This salt is hygroscopic and e ...
(in deodorants),
zinc pyrithione
Zinc pyrithione (or pyrithione zinc) is a coordination complex of zinc. It has fungistatic (inhibiting the division of fungal cells) and bacteriostatic (inhibiting bacterial cell division) properties and is used in the treatment of seborrhoeic d ...
(anti-
dandruff
Dandruff is a skin condition that mainly affects the scalp. Symptoms include flaking and sometimes mild itchiness. It can result in social or self-esteem problems. A more severe form of the condition, which includes inflammation of the skin, ...
shampoos), zinc sulfide (in luminescent paints), and
dimethylzinc
Dimethylzinc, also known as Zinc methyl, DMZ, or DMZn is a colorless volatile liquid Zn(CH3)2, formed by the action of methyl iodide on zinc at elevated temperature or on zinc sodium alloy.
:2Zn + 2CH3I → Zn(CH3)2 + ZnI2
The sodium assists the ...
or
diethylzinc
Diethylzinc (C2H5)2Zn, or DEZ, is a highly pyrophoric and reactive organozinc compound consisting of a zinc center bound to two ethyl groups. This colourless liquid is an important reagent in organic chemistry. It is available commercially as a ...
in the organic laboratory.
Characteristics
Physical properties
Zinc is a bluish-white, lustrous,
diamagnetic
Diamagnetic materials are repelled by a magnetic field; an applied magnetic field creates an induced magnetic field in them in the opposite direction, causing a repulsive force. In contrast, paramagnetic and ferromagnetic materials are attracted ...
metal,
though most common commercial grades of the metal have a dull finish.
It is somewhat less dense than
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
and has a hexagonal
crystal structure
In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystal, crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric pat ...
, with a distorted form of
hexagonal close packing
In geometry, close-packing of equal spheres is a dense arrangement of congruent spheres in an infinite, regular arrangement (or lattice). Carl Friedrich Gauss proved that the highest average density – that is, the greatest fraction of space occu ...
, in which each atom has six nearest neighbors (at 265.9 pm) in its own plane and six others at a greater distance of 290.6 pm. The metal is hard and brittle at most temperatures but becomes malleable between 100 and 150 °C.
Above 210 °C, the metal becomes brittle again and can be pulverized by beating. Zinc is a fair
conductor of electricity.
For a metal, zinc has relatively low melting (419.5 °C) and boiling point (907 °C).
The melting point is the lowest of all the
d-block
A block of the periodic table is a set of elements unified by the atomic orbitals their valence electrons or vacancies lie in. The term appears to have been first used by Charles Janet. Each block is named after its characteristic orbital: s-blo ...
metals aside from
mercury
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
and
cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...
; for this reason among others, zinc, cadmium, and mercury are often not considered to be
transition metal
In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that can ...
s like the rest of the d-block metals.
Many
alloy
An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...
s contain zinc, including brass. Other metals long known to form binary alloys with zinc are
aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
,
antimony
Antimony is a chemical element with the symbol Sb (from la, stibium) and atomic number 51. A lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb2S3). Antimony compounds have been known since ancient time ...
,
bismuth
Bismuth is a chemical element with the Symbol (chemistry), symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental ...
,
gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile met ...
, iron,
lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
, mercury,
silver
Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...
,
tin
Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal.
Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...
,
magnesium
Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
,
cobalt
Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, pr ...
,
nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...
,
tellurium
Tellurium is a chemical element with the symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally fou ...
, and
sodium
Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable iso ...
. Although neither zinc nor
zirconium
Zirconium is a chemical element with the symbol Zr and atomic number 40. The name ''zirconium'' is taken from the name of the mineral zircon, the most important source of zirconium. The word is related to Persian '' zargun'' (zircon; ''zar-gun'', ...
is
ferromagnetic
Ferromagnetism is a property of certain materials (such as iron) which results in a large observed magnetic permeability, and in many cases a large magnetic coercivity allowing the material to form a permanent magnet. Ferromagnetic materials ...
, their alloy, , exhibits ferromagnetism below 35
K.
Occurrence
Zinc makes up about 75
ppm (0.0075%) of
Earth's crust
Earth's crust is Earth's thin outer shell of rock, referring to less than 1% of Earth's radius and volume. It is the top component of the lithosphere, a division of Earth's layers that includes the crust and the upper part of the mantle. The ...
, making it the 24th most abundant element. Typical background concentrations of zinc do not exceed 1 μg/m
3 in the atmosphere; 300 mg/kg in soil; 100 mg/kg in vegetation; 20 μg/L in freshwater and 5 μg/L in seawater. The element is normally found in association with other
base metal
A base metal is a common and inexpensive metal, as opposed to a precious metal such as gold or silver. In numismatics, coins often derived their value from the precious metal content; however, base metals have also been used in coins in the past ...
s such as
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
and
lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
in
ore
Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 Apr ...
s.
Zinc is a
chalcophile
The Goldschmidt classification,
developed by Victor Goldschmidt (1888–1947), is a geochemical classification which groups the chemical elements within the Earth according to their preferred host phases into lithophile (Rock (geology), rock-lovi ...
, meaning the element is more likely to be found in minerals together with
sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
and other heavy
chalcogen
The chalcogens (ore forming) ( ) are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioac ...
s, rather than with the light chalcogen
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
or with non-chalcogen electronegative elements such as the
halogen
The halogens () are a group in the periodic table consisting of five or six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). In the modern IUPAC nomenclature, this group is ...
s.
Sulfide
Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds lar ...
s formed as the crust solidified under the
reducing conditions of the early Earth's atmosphere.
Sphalerite
Sphalerite (sometimes spelled sphaelerite) is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in Sedimentary exhalative deposits, sedimen ...
, which is a form of zinc sulfide, is the most heavily mined zinc-containing ore because its concentrate contains 60–62% zinc.
Other source minerals for zinc include
smithsonite
Smithsonite, also known as zinc spar, is the mineral form of zinc carbonate ( Zn CO3). Historically, smithsonite was identified with hemimorphite before it was realized that they were two different minerals. The two minerals are very similar in a ...
(zinc
carbonate
A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...
),
hemimorphite
Hemimorphite is the chemical compound Zn4( Si2O7)( OH)2 ·H2O, a component of mineral calamine. It is a silicate mineral which, together with smithsonite (ZnCO3), has been historically mined from the upper parts of zinc and lead ores. Both ...
(zinc
silicate
In chemistry, a silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name is al ...
),
wurtzite
Wurtzite is a zinc and iron sulfide mineral with the chemical formula , a less frequently encountered Polymorphism (materials science), structural polymorph form of sphalerite. The iron content is variable up to eight percent.Palache, Charles, Har ...
(another zinc sulfide), and sometimes
hydrozincite
Hydrozincite, also known as zinc bloom or marionite, is a white carbonate mineral consisting of Zn5( CO3)2( OH)6. It is usually found in massive rather than crystalline form.
It occurs as an oxidation product of zinc ores and as post mine incru ...
(basic
zinc carbonate
Zinc carbonate is the inorganic compound with the formula ZnCO3. It is a white solid that is insoluble in water. It exists in nature as the mineral smithsonite. It is prepared by treating cold solutions of zinc sulfate with potassium bicarbonat ...
).
With the exception of wurtzite, all these other minerals were formed by weathering of the primordial zinc sulfides.
Identified world zinc resources total about 1.9–2.8 billion
tonne
The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
s.
Large deposits are in Australia, Canada and the United States, with the largest reserves in
Iran
Iran, officially the Islamic Republic of Iran, and also called Persia, is a country located in Western Asia. It is bordered by Iraq and Turkey to the west, by Azerbaijan and Armenia to the northwest, by the Caspian Sea and Turkmeni ...
.
The most recent estimate of reserve base for zinc (meets specified minimum physical criteria related to current mining and production practices) was made in 2009 and calculated to be roughly 480 Mt.
Zinc reserves, on the other hand, are geologically identified ore bodies whose suitability for recovery is economically based (location, grade, quality, and quantity) at the time of determination. Since exploration and mine development is an ongoing process, the amount of zinc reserves is not a fixed number and sustainability of zinc ore supplies cannot be judged by simply extrapolating the combined mine life of today's zinc mines. This concept is well supported by data from the United States Geological Survey (USGS), which illustrates that although refined zinc production increased 80% between 1990 and 2010, the reserve lifetime for zinc has remained unchanged. About 346 million tonnes have been extracted throughout history to 2002, and scholars have estimated that about 109–305 million tonnes are in use.
Isotopes
Five stable
isotope
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...
s of zinc occur in nature, with
64Zn being the most abundant isotope (49.17%
natural abundance
In physics, natural abundance (NA) refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass (a weighted average, weighted by mole-fraction abundance figures) of these isotopes is the atomi ...
).
The other isotopes found in nature are (27.73%), (4.04%), (18.45%), and (0.61%).
Several dozen
radioisotope
A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...
s have been characterized. , which has a half-life of 243.66 days, is the least active radioisotope, followed by with a half-life of 46.5 hours.
Zinc has 10
nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy excited state, higher energy levels than in the ground state of the same nucleus. "Metastable" describes nuclei whose excited ...
s, of which
69mZn has the longest half-life, 13.76 h.
The superscript ''m'' indicates a
metastable
In chemistry and physics, metastability denotes an intermediate Energy level, energetic state within a dynamical system other than the system's ground state, state of least energy.
A ball resting in a hollow on a slope is a simple example of me ...
isotope. The nucleus of a metastable isotope is in an
excited state and will return to the
ground state
The ground state of a quantum-mechanical system is its stationary state of lowest energy; the energy of the ground state is known as the zero-point energy of the system. An excited state is any state with energy greater than the ground state. ...
by emitting a
photon
A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they always ...
in the form of a
gamma ray
A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
. has three excited metastable states and has two. The isotopes , , and each have only one excited metastable state.
The most common
decay mode of a
radioisotope
A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...
of zinc with a
mass number
The mass number (symbol ''A'', from the German word ''Atomgewicht'' tomic weight, also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus. It is approxima ...
lower than 66 is
electron capture
Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. Thi ...
. The
decay product resulting from electron capture is an isotope of copper.
: + →
The most common decay mode of a radioisotope of zinc with mass number higher than 66 is
beta decay
In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For ...
(β
−), which produces an isotope of
gallium
Gallium is a chemical element with the symbol Ga and atomic number 31. Discovered by French chemist Paul-Émile Lecoq de Boisbaudran in 1875, Gallium is in group 13 of the periodic table and is similar to the other metals of the group (aluminiu ...
.
: → + +
Compounds and chemistry
Reactivity
Zinc has an
electron configuration of
rd
104s
2 and is a member of the
group 12 of the
periodic table
The periodic table, also known as the periodic table of the (chemical) elements, is a rows and columns arrangement of the chemical elements. It is widely used in chemistry, physics, and other sciences, and is generally seen as an icon of ch ...
. It is a moderately reactive
metal
A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...
and strong
reducing agent
In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ).
Examples of substances that are commonly reducing agents include the Earth meta ...
.
The surface of the pure metal tarnishes quickly, eventually forming a protective Passivation (chemistry), passivating layer of the basic Hydrozincite, zinc carbonate, , by reaction with atmospheric carbon dioxide.
Zinc burns in air with a bright bluish-green flame, giving off fumes of zinc oxide.
Zinc reacts readily with acids, alkalis and other non-metals. Extremely pure zinc reacts only slowly at
room temperature
Colloquially, "room temperature" is a range of air temperatures that most people prefer for indoor settings. It feels comfortable to a person when they are wearing typical indoor clothing. Human comfort can extend beyond this range depending on ...
with acids.
Strong acids, such as hydrochloric acid, hydrochloric or sulfuric acid, can remove the passivating layer and the subsequent reaction with the acid releases hydrogen gas.
The chemistry of zinc is dominated by the +2 oxidation state. When compounds in this oxidation state are formed, the outer electron shell, shell ''s'' electrons are lost, yielding a bare zinc ion with the electronic configuration
rd
10. In aqueous solution an octahedral complex, is the predominant species. The volatilization of zinc in combination with zinc chloride at temperatures above 285 °C indicates the formation of , a zinc compound with a +1 oxidation state.
No compounds of zinc in positive oxidation states other than +1 or +2 are known. Calculations indicate that a zinc compound with the oxidation state of +4 is unlikely to exist. Zn(III) is predicted to exist in the presence of strongly electronegative trianions; however, there exists some doubt around this possibility. But in 2021 another compound was reported with more evidence that had the oxidation state of +3 with the formula ZnBeB
11(CN)
12.
Zinc chemistry is similar to the chemistry of the late first-row transition metals,
nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...
and copper, though it has a filled d-shell and compounds are
diamagnetic
Diamagnetic materials are repelled by a magnetic field; an applied magnetic field creates an induced magnetic field in them in the opposite direction, causing a repulsive force. In contrast, paramagnetic and ferromagnetic materials are attracted ...
and mostly colorless.
The ionic radii of zinc and magnesium happen to be nearly identical. Because of this some of the equivalent salts have the same
crystal structure
In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystal, crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric pat ...
, and in other circumstances where ionic radius is a determining factor, the chemistry of zinc has much in common with that of magnesium.
In other respects, there is little similarity with the late first-row transition metals. Zinc tends to form bonds with a greater degree of covalency and much more stable Complex (chemistry), complexes with nitrogen, N- and sulfur, S- donors.
Complexes of zinc are mostly 4- or 6- coordinate covalent bond, coordinate, although 5-coordinate complexes are known.
Zinc(I) compounds
Zinc(I) compounds are very rare. The [Zn
2]
2+ ion is implicated by the formation of a yellow diamagnetic glass by dissolving metallic zinc in molten ZnCl
2. The [Zn
2]
2+ core would be analogous to the [Hg
2]
2+ cation present in
mercury
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
(I) compounds. The diamagnetism, diamagnetic nature of the ion confirms its dimeric structure. The first zinc(I) compound containing the Zn–Zn bond, Decamethyldizincocene, (η
5-C
5Me
5)
2Zn
2.
Zinc(II) compounds
![Zinc chloride](https://upload.wikimedia.org/wikipedia/commons/3/37/Zinc_chloride.jpg)
Binary compounds of zinc are known for most of the metalloids and all the nonmetals except the noble gases. The oxide zinc oxide, ZnO is a white powder that is nearly insoluble in neutral aqueous solutions, but is amphoteric, dissolving in both strong basic and acidic solutions.
The other
chalcogen
The chalcogens (ore forming) ( ) are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioac ...
ides (zinc sulfide, ZnS, zinc selenide, ZnSe, and zinc telluride, ZnTe) have varied applications in electronics and optics. Pnictogenides (Zinc nitride, , zinc phosphide, , zinc arsenide, and zinc antimonide, ), the peroxide (zinc peroxide, ), the hydride (zinc hydride, ), and the carbide () are also known. Of the four halides, zinc fluoride, has the most ionic character, while the others (zinc chloride, , zinc bromide, , and zinc iodide, ) have relatively low melting points and are considered to have more covalent character.
In weak basic solutions containing ions, the hydroxide Zinc hydroxide, forms as a white precipitate. In stronger alkaline solutions, this hydroxide is dissolved to form zincates (zincate, ).
The nitrate Zinc nitrate, , chlorate Zinc chlorate, , sulfate Zinc sulfate, , phosphate Zinc phosphate, , molybdate Zinc molybdate, , cyanide Zinc cyanide, , arsenite , arsenate and the chromate Zinc chromate, (one of the few colored zinc compounds) are a few examples of other common inorganic compounds of zinc.
Organozinc compounds are those that contain zinc–carbon covalent bonds. Diethylzinc (Diethylzinc, ) is a reagent in synthetic chemistry. It was first reported in 1848 from the reaction of zinc and ethyl iodide, and was the first compound known to contain a metal–carbon sigma bond.
Test for zinc
Cobalticyanide paper (Rinnmann's test for Zn) can be used as a chemical indicator for zinc. 4 g of K
3Co(CN)
6 and 1 g of KClO
3 is dissolved on 100 ml of water. Paper is dipped in the solution and dried at 100 °C. One drop of the sample is dropped onto the dry paper and heated. A green disc indicates the presence of zinc.
History
Ancient use
The Charaka Samhita, thought to have been written between 300 and 500 AD, mentions a metal which, when oxidized, produces ''pushpanjan'', thought to be zinc oxide. Zinc mines at Zawar, near Udaipur in India, have been active since the Mauryan period ( and 187 BCE). The smelting of metallic zinc here, however, appears to have begun around the 12th century AD.
[p. 46, Ancient mining and metallurgy in Rajasthan, S. M. Gandhi, chapter 2 in ''Crustal Evolution and Metallogeny in the Northwestern Indian Shield: A Festschrift for Asoke Mookherjee'', M. Deb, ed., Alpha Science Int'l Ltd., 2000, .] One estimate is that this location produced an estimated million tonnes of metallic zinc and zinc oxide from the 12th to 16th centuries.
Another estimate gives a total production of 60,000 tonnes of metallic zinc over this period.
The Rasaratna Samuccaya, written in approximately the 13th century AD, mentions two types of zinc-containing ores: one used for metal extraction and another used for medicinal purposes.
![Hemmoorer Eimer](https://upload.wikimedia.org/wikipedia/commons/6/66/Hemmoorer_Eimer.jpg)
Various isolated examples of the use of impure zinc in ancient times have been discovered. Zinc ores were used to make the zinc–copper alloy brass thousands of years prior to the discovery of zinc as a separate element. Judean brass from the 14th to 10th centuries BC contains 23% zinc.
Knowledge of how to produce brass spread to Ancient Greece by the 7th century BC, but few varieties were made.
Ornaments made of
alloy
An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...
s containing 80–90% zinc, with lead, iron,
antimony
Antimony is a chemical element with the symbol Sb (from la, stibium) and atomic number 51. A lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb2S3). Antimony compounds have been known since ancient time ...
, and other metals making up the remainder, have been found that are 2,500 years old.
A possibly prehistoric statuette containing 87.5% zinc was found in a Dacian archaeological site.
The oldest known pills were made of the zinc carbonates hydrozincite and smithsonite. The pills were used for sore eyes and were found aboard the Roman ship Relitto del Pozzino, wrecked in 140 BC.
The manufacture of brass was known to the Ancient Rome, Romans by about 30 BC.
They made brass by heating powdered Calamine (mineral), calamine (zinc
silicate
In chemistry, a silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name is al ...
or carbonate), charcoal and copper together in a crucible.
The resulting calamine brass was then either cast or hammered into shape for use in weaponry. Some coins struck by Romans in the Christian era are made of what is probably calamine brass.
Strabo writing in the 1st century BC (but quoting a now lost work of the 4th century BC historian Theopompus) mentions "drops of false silver" which when mixed with copper make brass. This may refer to small quantities of zinc that is a by-product of smelting sulfide ores. Zinc in such remnants in smelting ovens was usually discarded as it was thought to be worthless.
The Berne zinc tablet is a votive plaque dating to Roman Gaul made of an alloy that is mostly zinc.
Early studies and naming
Zinc was distinctly recognized as a metal under the designation of ''Yasada'' or Jasada in the medical Lexicon ascribed to the Hindu king Madanapala (of Taka dynasty) and written about the year 1374.
[ (public domain text)] Smelting and extraction of impure zinc by reducing calamine with wool and other organic substances was accomplished in the 13th century in India.
The Chinese did not learn of the technique until the 17th century.
![Zinc-alchemy symbols](https://upload.wikimedia.org/wikipedia/commons/a/a2/Zinc-alchemy_symbols.png)
Alchemy, Alchemists burned zinc metal in air and collected the resulting zinc oxide on a Condenser (heat transfer), condenser. Some alchemists called this zinc oxide ''lana philosophica'', Latin for "philosopher's wool", because it collected in wooly tufts, whereas others thought it looked like white snow and named it ''nix album''.
The name of the metal was probably first documented by
Paracelsus, a Swiss-born German alchemist, who referred to the metal as "zincum" or "zinken" in his book ''Liber Mineralium II'', in the 16th century.
The word is probably derived from the German , and supposedly meant "tooth-like, pointed or jagged" (metallic zinc crystals have a needle-like appearance). ''Zink'' could also imply "tin-like" because of its relation to German ''zinn'' meaning tin. Yet another possibility is that the word is derived from the Persian language, Persian word ''seng'' meaning stone. The metal was also called Indian tin, tutanego, calamine, and spinter.
German metallurgist Andreas Libavius received a quantity of what he called "calay" of Malabar from a cargo ship captured from the Portuguese in the year 1596. Libavius described the properties of the sample, which may have been zinc. Zinc was regularly imported to Europe from the Orient in the 17th and early 18th centuries,
but was at times very expensive.
[An East India Company ship carrying a cargo of nearly pure zinc metal from the Orient sank off the coast Sweden in 1745.]
Isolation
![Andreas Sigismund Marggraf-flip](https://upload.wikimedia.org/wikipedia/commons/8/85/Andreas_Sigismund_Marggraf-flip.jpg)
Metallic zinc was isolated in India by 1300 AD, much earlier than in the West. Before it was isolated in Europe, it was imported from India in about 1600 CE.
Postlewayt, Postlewayt's ''Universal Dictionary'', a contemporary source giving technological information in Europe, did not mention zinc before 1751 but the element was studied before then.
Flemish metallurgist and alchemist P. M. de Respour reported that he had extracted metallic zinc from zinc oxide in 1668.
By the start of the 18th century, Étienne François Geoffroy described how zinc oxide condenses as yellow crystals on bars of iron placed above zinc ore that is being smelted.
In Britain, John Lane (metallurgist), John Lane is said to have carried out experiments to smelt zinc, probably at Landore, prior to his bankruptcy in 1726.
In 1738 in Great Britain, William Champion (metallurgist), William Champion patented a process to extract zinc from calamine in a vertical retort-style smelter. His technique resembled that used at Zawar zinc mines in
Rajasthan
Rajasthan (; lit. 'Land of Kings') is a state in northern India. It covers or 10.4 per cent of India's total geographical area. It is the largest Indian state by area and the seventh largest by population. It is on India's northwestern si ...
, but no evidence suggests he visited the Orient.
Champion's process was used through 1851.
German chemist Andreas Sigismund Marggraf, Andreas Marggraf normally gets credit for discovering pure metallic zinc, even though Swedish chemist Anton von Swab had distilled zinc from calamine four years previously.
In his 1746 experiment, Marggraf heated a mixture of calamine and charcoal in a closed vessel without copper to obtain a metal.
This procedure became commercially practical by 1752.
Later work
![Luigi Galvani, oil-painting](https://upload.wikimedia.org/wikipedia/commons/5/51/Luigi_Galvani%2C_oil-painting.jpg)
William Champion's brother, John, patented a process in 1758 for calcining zinc sulfide into an oxide usable in the retort process.
Prior to this, only calamine could be used to produce zinc. In 1798, Johann Christian Ruberg improved on the smelting process by building the first horizontal retort smelter. Jean-Jacques Daniel Dony built a different kind of horizontal zinc smelter in Belgium that processed even more zinc.
Italian doctor
Luigi Galvani discovered in 1780 that connecting the spinal cord of a freshly dissected frog to an iron rail attached by a brass hook caused the frog's leg to twitch.
He incorrectly thought he had discovered an ability of nerves and muscles to create
electricity
Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described ...
and called the effect "bioelectricity, animal electricity".
The galvanic cell and the process of galvanization were both named for Luigi Galvani, and his discoveries paved the way for Battery (electricity), electrical batteries, galvanization, and cathodic protection.
Galvani's friend,
Alessandro Volta
Alessandro Giuseppe Antonio Anastasio Volta (, ; 18 February 1745 – 5 March 1827) was an Italian physicist, chemist and lay Catholic who was a pioneer of electricity and power who is credited as the inventor of the electric battery and the ...
, continued researching the effect and invented the Voltaic pile in 1800.
Volta's pile consisted of a stack of simplified galvanic cells, each being one plate of copper and one of zinc connected by an electrolyte. By stacking these units in series, the Voltaic pile (or "battery") as a whole had a higher voltage, which could be used more easily than single cells. Electricity is produced because the Volta potential between the two metal plates makes electrons flow from the zinc to the copper and corrode the zinc.
The non-magnetic character of zinc and its lack of color in solution delayed discovery of its importance to biochemistry and nutrition.
This changed in 1940 when carbonic anhydrase, an enzyme that scrubs carbon dioxide from blood, was shown to have zinc in its active site.
The digestive enzyme carboxypeptidase became the second known zinc-containing enzyme in 1955.
Production
Mining and processing
![Skorpion Zink Mine](https://upload.wikimedia.org/wikipedia/commons/1/10/Skorpion_Zink_Mine.jpg)
Zinc is the fourth most common metal in use, trailing only
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
,
aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
, and
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
with an annual production of about 13 million tonnes.
The world's largest zinc producer is Nyrstar, a merger of the Australian OZ Minerals and the Belgian Umicore. About 70% of the world's zinc originates from mining, while the remaining 30% comes from recycling secondary zinc.
Commercially pure zinc is known as Special High Grade, often abbreviated ''SHG'', and is 99.995% pure.
Worldwide, 95% of new zinc is mined from sulfide, sulfidic ore deposits, in which sphalerite (ZnS) is nearly always mixed with the sulfides of copper, lead and iron.
Zinc mines are scattered throughout the world, with the main areas being China, Australia, and Peru. China produced 38% of the global zinc output in 2014.
Zinc metal is produced using extractive metallurgy.
The ore is finely ground, then put through
froth flotation
Froth flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is used in mineral processing, paper recycling and waste-water treatment industries. Historically this was first used in the mining industry, wher ...
to separate minerals from gangue (on the property of hydrophobicity), to get a zinc sulfide ore concentrate
consisting of about 50% zinc, 32% sulfur, 13% iron, and 5% .
Roasting (metallurgy), Roasting converts the zinc sulfide concentrate to zinc oxide:
:
2ZnS + 3O2 ->[t^o] 2ZnO + 2SO2
The sulfur dioxide is used for the production of sulfuric acid, which is necessary for the leaching process. If deposits of
zinc carbonate
Zinc carbonate is the inorganic compound with the formula ZnCO3. It is a white solid that is insoluble in water. It exists in nature as the mineral smithsonite. It is prepared by treating cold solutions of zinc sulfate with potassium bicarbonat ...
, zinc silicate, or zinc-spinel (like the Skorpion Zinc, Skorpion Deposit in Namibia) are used for zinc production, the roasting can be omitted.
For further processing two basic methods are used: pyrometallurgy or
electrowinning. Pyrometallurgy reduces zinc oxide with carbon or carbon monoxide at into the metal, which is distilled as zinc vapor to separate it from other metals, which are not volatile at those temperatures. The zinc vapor is collected in a condenser.
The equations below describe this process:
:
ZnO + C ->[950^oC] Zn + CO
:
ZnO + CO ->[950^oC] Zn + CO2
In
electrowinning, zinc is leached from the ore concentrate by sulfuric acid and impurities are precipitated:
:
ZnO + H2SO4 -> ZnSO4 + H2O
Finally, the zinc is reduced by electrolysis.
:
2ZnSO4 + 2H2O -> 2Zn + O2 + 2H2SO4
The sulfuric acid is regenerated and recycled to the leaching step.
When galvanised feedstock is fed to an electric arc furnace, the zinc is recovered from the dust by a number of processes, predominantly the Waelz process (90% as of 2014).
Environmental impact
Refinement of sulfidic zinc ores produces large volumes of sulfur dioxide and
cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...
vapor. Smelter slag and other residues contain significant quantities of metals. About 1.1 million tonnes of metallic zinc and 130 thousand tonnes of lead were mined and smelted in the Belgian towns of Kelmis, La Calamine and Plombières between 1806 and 1882.
The dumps of the past mining operations leach zinc and cadmium, and the sediments of the Geul River contain non-trivial amounts of metals.
About two thousand years ago, emissions of zinc from mining and smelting totaled 10 thousand tonnes a year. After increasing 10-fold from 1850, zinc emissions peaked at 3.4 million tonnes per year in the 1980s and declined to 2.7 million tonnes in the 1990s, although a 2005 study of the Arctic troposphere found that the concentrations there did not reflect the decline. Man-made and natural emissions occur at a ratio of 20 to 1.
Zinc in rivers flowing through industrial and mining areas can be as high as 20 ppm.
Effective sewage treatment greatly reduces this; treatment along the Rhine, for example, has decreased zinc levels to 50 ppb.
Concentrations of zinc as low as 2 ppm adversely affects the amount of oxygen that fish can carry in their blood.
soil contamination, Soils contaminated with zinc from mining, refining, or fertilizing with zinc-bearing sludge can contain several grams of zinc per kilogram of dry soil. Levels of zinc in excess of 500 ppm in soil interfere with the ability of plants to absorb other Dietary mineral, essential metals, such as iron and manganese. Zinc levels of 2000 ppm to 180,000 ppm (18%) have been recorded in some soil samples.
Applications
Major applications of zinc include (numbers are given for the US)
# Galvanization, Galvanizing (55%)
#
Brass
Brass is an alloy of copper (Cu) and zinc (Zn), in proportions which can be varied to achieve different mechanical, electrical, and chemical properties. It is a substitutional alloy: atoms of the two constituents may replace each other with ...
and bronze (16%)
# Other alloys (21%)
# Miscellaneous (8%)
Anti-corrosion and batteries
![Feuerverzinkte Oberfläche](https://upload.wikimedia.org/wikipedia/commons/c/c4/Feuerverzinkte_Oberfl%C3%A4che.jpg)
Zinc is most commonly used as an anti-corrosion agent,
and galvanization (coating of
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
or steel) is the most familiar form. In 2009 in the United States, 55% or 893,000 tons of the zinc metal was used for galvanization.
Zinc is more reactive than iron or steel and thus will attract almost all local oxidation until it completely corrodes away.
A protective surface layer of oxide and carbonate ( forms as the zinc corrodes.
This protection lasts even after the zinc layer is scratched but degrades through time as the zinc corrodes away.
The zinc is applied electrochemically or as molten zinc by
hot-dip galvanizing
Hot-dip galvanization is a form of galvanization. It is the process of coating iron and steel with zinc, which alloys with the surface of the base metal when immersing the metal in a bath of molten zinc at a temperature of around . When expose ...
or spraying. Galvanization is used on chain-link fencing, guard rails, suspension bridges, lightposts, metal roofs, heat exchangers, and car bodies.
The relative reactivity of zinc and its ability to attract oxidation to itself makes it an efficient sacrificial anode in cathodic protection (CP). For example, cathodic protection of a buried pipeline can be achieved by connecting anodes made from zinc to the pipe.
Zinc acts as the anode (negative terminus) by slowly corroding away as it passes electric current to the steel pipeline.
[Electric current will naturally flow between zinc and steel but in some circumstances inert anodes are used with an external DC source.] Zinc is also used to cathodically protect metals that are exposed to sea water. A zinc disc attached to a ship's iron rudder will slowly corrode while the rudder stays intact.
Similarly, a zinc plug attached to a propeller or the metal protective guard for the keel of the ship provides temporary protection.
With a standard electrode potential (SEP) of −0.76 volts, zinc is used as an anode material for batteries. (More reactive lithium (SEP −3.04 V) is used for anodes in Lithium battery, lithium batteries ). Powdered zinc is used in this way in alkaline battery, alkaline batteries and the case (which also serves as the anode) of Zinc–carbon battery, zinc–carbon batteries is formed from sheet zinc. Zinc is used as the anode or fuel of the zinc–air battery/fuel cell. The Zinc–cerium battery, zinc-cerium redox flow battery also relies on a zinc-based negative half-cell.
Alloys
A widely used zinc alloy is brass, in which copper is alloyed with anywhere from 3% to 45% zinc, depending upon the type of brass.
Brass is generally more ductile and stronger than copper, and has superior corrosion resistance.
These properties make it useful in communication equipment, hardware, musical instruments, and water valves.
![Microstructure of rolled and annealed brass; magnification 400X](https://upload.wikimedia.org/wikipedia/commons/6/69/Microstructure_of_rolled_and_annealed_brass%3B_magnification_400X.jpg)
Other widely used zinc alloys include nickel silver, typewriter metal, soft and aluminium solder, and commercial bronze.
Zinc is also used in contemporary pipe organs as a substitute for the traditional lead/tin alloy in pipes. Alloys of 85–88% zinc, 4–10% copper, and 2–8% aluminium find limited use in certain types of machine bearings. Zinc has been the primary metal in Lincoln cent, American one cent coins (pennies) since 1982.
The zinc core is coated with a thin layer of copper to give the appearance of a copper coin. In 1994, of zinc were used to produce 13.6 billion pennies in the United States.
Alloys of zinc with small amounts of copper, aluminium, and magnesium are useful in die casting as well as spin casting, especially in the automotive, electrical, and hardware industries.
These alloys are marketed under the name Zamak. An example of this is zinc aluminium. The low melting point together with the low viscosity of the alloy makes possible the production of small and intricate shapes. The low working temperature leads to rapid cooling of the cast products and fast production for assembly.
Another alloy, marketed under the brand name Prestal, contains 78% zinc and 22% aluminium, and is reported to be nearly as strong as steel but as malleable as plastic.
This superplasticity of the alloy allows it to be molded using die casts made of ceramics and cement.
Similar alloys with the addition of a small amount of lead can be cold-rolled into sheets. An alloy of 96% zinc and 4% aluminium is used to make stamping dies for low production run applications for which ferrous metal dies would be too expensive.
For building facades, roofing, and other applications for sheet metal formed by deep drawing, roll forming, or bending (metalworking), bending, zinc alloys with titanium and copper are used.
Unalloyed zinc is too brittle for these manufacturing processes.
As a dense, inexpensive, easily worked material, zinc is used as a
lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
replacement. In the wake of Lead poisoning, lead concerns, zinc appears in weights for various applications ranging from fishing to tire balances and flywheels.
Cadmium zinc telluride (CZT) is a semiconductor, semiconductive alloy that can be divided into an array of small sensing devices.
These devices are similar to an integrated circuit and can detect the energy of incoming
gamma ray
A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
photons.
When behind an absorbing mask, the CZT sensor array can determine the direction of the rays.
Other industrial uses
![Zinc oxide](https://upload.wikimedia.org/wikipedia/commons/1/13/Zinc_oxide.jpg)
Roughly one quarter of all zinc output in the United States in 2009 was consumed in zinc compounds;
a variety of which are used industrially. Zinc oxide is widely used as a white pigment in paints and as a catalyst in the manufacture of rubber to disperse heat. Zinc oxide is used to protect rubber polymers and plastics from ultraviolet radiation (UV).
The semiconductor properties of zinc oxide make it useful in varistors and photocopying products. The zinc zinc-oxide cycle is a two step Thermochemistry, thermochemical process based on zinc and zinc oxide for hydrogen production.
Zinc chloride is often added to lumber as a fire retardant
and sometimes as a wood preservative. It is used in the manufacture of other chemicals.
Zinc methyl () is used in a number of organic organic synthesis, syntheses. Zinc sulfide (ZnS) is used in luminescence, luminescent pigments such as on the hands of clocks, X-ray and television screens, and luminous paints.
Crystals of ZnS are used in lasers that operate in the mid-infrared part of the spectrum. Zinc sulfate is a chemical in dyes and pigments.
Zinc pyrithione is used in antifouling paints.
Zinc powder is sometimes used as a propellant in model rockets.
When a compressed mixture of 70% zinc and 30%
sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
powder is ignited there is a violent chemical reaction.
This produces zinc sulfide, together with large amounts of hot gas, heat, and light.
Zinc sheet metal is used as a durable covering for roofs, walls, and countertops, the last often seen in bistros and oyster bars, and is known for the rustic look imparted by its surface oxidation in use to a blue-gray patina and susceptibility to scratching.
, the most abundant isotope of zinc, is very susceptible to neutron activation, being Nuclear transmutation, transmuted into the highly radioactive , which has a half-life of 244 days and produces intense gamma ray, gamma radiation. Because of this, zinc oxide used in nuclear reactors as an anti-corrosion agent is depleted of before use, this is called depleted zinc oxide. For the same reason, zinc has been proposed as a Salted bomb, salting material for nuclear weapons (
cobalt
Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, pr ...
is another, better-known salting material).
A jacket of Isotope separation, isotopically enriched would be irradiated by the intense high-energy neutron flux from an exploding thermonuclear weapon, forming a large amount of significantly increasing the radioactivity of the weapon's Nuclear fallout, fallout.
Such a weapon is not known to have ever been built, tested, or used.
is used as a isotopic tracer, tracer to study how alloys that contain zinc wear out, or the path and the role of zinc in organisms.
Zinc dithiocarbamate complexes are used as agricultural fungicides; these include Zineb, Metiram, Propineb and Ziram. Zinc naphthenate is used as wood preservative. Zinc in the form of Zinc dithiophosphate, ZDDP, is used as an anti-wear additive for metal parts in engine oil.
Organic chemistry
![DiphenylzincCarbonylAddition](https://upload.wikimedia.org/wikipedia/commons/4/4f/DiphenylzincCarbonylAddition.png)
Organozinc compound, Organozinc chemistry is the science of compounds that contain carbon-zinc bonds, describing the physical properties, synthesis, and chemical reactions. Many organozinc compounds are important. Among important applications are
* The Frankland-Duppa Reaction in which an oxalate ester (ROCOCOOR) reacts with an alkyl halide R'X, zinc and hydrochloric acid to form the α-hydroxycarboxylic esters RR'COHCOOR
* On the downside, organozincs are much less nucleophilic than Grignards, and they are expensive and difficult to handle. Commercially available diorganozinc compounds are
dimethylzinc
Dimethylzinc, also known as Zinc methyl, DMZ, or DMZn is a colorless volatile liquid Zn(CH3)2, formed by the action of methyl iodide on zinc at elevated temperature or on zinc sodium alloy.
:2Zn + 2CH3I → Zn(CH3)2 + ZnI2
The sodium assists the ...
,
diethylzinc
Diethylzinc (C2H5)2Zn, or DEZ, is a highly pyrophoric and reactive organozinc compound consisting of a zinc center bound to two ethyl groups. This colourless liquid is an important reagent in organic chemistry. It is available commercially as a ...
and diphenylzinc. In one study, the active organozinc compound is obtained from much cheaper organobromine compound, organobromine precursors.
Zinc has found many uses as a catalyst in organic synthesis including asymmetric synthesis, being cheap and easily available alternative to precious metal complexes. The results (yield and enantiomeric excess) obtained with chiral zinc catalysts are comparable to those achieved with palladium, ruthenium, iridium and others, and zinc becomes a metal catalyst of choice.
Dietary supplement
![Zinc 50 mg](https://upload.wikimedia.org/wikipedia/commons/7/7c/Zinc_50_mg.jpg)
In most single-tablet, over-the-counter, daily vitamin and Dietary mineral, mineral supplements, zinc is included in such forms as zinc oxide, zinc acetate,
zinc gluconate
Zinc gluconate is the zinc salt of gluconic acid. It is an ionic compound consisting of two anions of gluconate for each zinc(II) cation. Zinc gluconate is a popular form for the delivery of zinc as a dietary supplement providing 14.35% eleme ...
, or zinc amino acid chelate.
Generally, zinc supplement is recommended where there is high risk of zinc deficiency (such as low and middle income countries) as a preventive measure. Although zinc sulfate is a commonly used zinc form, zinc citrate, gluconate and picolinate may be valid options as well. These forms are better absorbed than zinc oxide.
Gastroenteritis
Zinc is an inexpensive and effective part of treatment of
diarrhea
Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin wi ...
among children in the developing world. Zinc becomes depleted in the body during diarrhea and replenishing zinc with a 10- to 14-day course of treatment can reduce the duration and severity of diarrheal episodes and may also prevent future episodes for as long as three months. Gastroenteritis is strongly attenuated by ingestion of zinc, possibly by direct antimicrobial action of the ions in the gastrointestinal tract, or by the absorption of the zinc and re-release from immune cells (all granulocytes secrete zinc), or both.
Common cold
Weight gain
Zinc deficiency may lead to loss of appetite. The use of zinc in the treatment of anorexia has been advocated since 1979. At least 15 clinical trials have shown that zinc improved weight gain in anorexia. A 1994 trial showed that zinc doubled the rate of body mass increase in the treatment of anorexia nervosa. Deficiency of other nutrients such as tyrosine, tryptophan and thiamine could contribute to this phenomenon of "malnutrition-induced malnutrition".
A meta-analysis of 33 prospective intervention trials regarding zinc supplementation and its effects on the growth of children in many countries showed that zinc supplementation alone had a statistically significant effect on linear growth and body weight gain, indicating that other deficiencies that may have been present were not responsible for growth retardation.
Other
A Cochrane review stated that people taking zinc supplement may be less likely to progress to age-related macular degeneration. Zinc supplement is an effective treatment for acrodermatitis enteropathica, a genetic disorder affecting zinc absorption that was previously fatal to affected infants.
Zinc deficiency has been associated with major depressive disorder (MDD), and zinc supplements may be an effective treatment.
Zinc may help individuals sleep more.
Topical use
Topical administration, Topical preparations of zinc include those used on the skin, often in the form of zinc oxide. Zinc oxide is generally recognised by the FDA as safe and effective and is considered a very photo-stable. Zinc oxide is one of the most common active ingredients formulated into a sunscreen to mitigate sunburn.
Applied thinly to a baby's diaper area (perineum) with each diaper change, it can protect against diaper rash.
Chelated zinc is used in toothpastes and mouthwashes to prevent halitosis, bad breath; zinc citrate helps reduce the build-up of Calculus (dental), calculus (tartar).
Zinc pyrithione is widely included in shampoos to prevent dandruff.
Topical zinc has also been shown to effectively treat, as well as prolong remission in genital herpes.
Biological role
Zinc is an essential
trace element
__NOTOC__
A trace element, also called minor element, is a chemical element whose concentration (or other measure of amount) is very low (a "trace amount"). They are classified into two groups: essential and non-essential. Essential trace elements ...
for humans
and other animals,
for plants
and for
microorganism
A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
s.
[Zinc's role in microorganisms is particularly reviewed in: ] Zinc is required for the function of over 300 enzymes and 1000 transcription factors,
and is stored and transferred in metallothioneins.
It is the second most abundant trace metal in humans after iron and it is the only metal which appears in all
enzyme classes.
In proteins, zinc ions are often coordinated to the amino acid side chains of aspartic acid, glutamic acid, cysteine and histidine. The theoretical and computational description of this zinc binding in proteins (as well as that of other transition metals) is difficult.
Roughly grams of zinc
are distributed throughout the human body. Most zinc is in the brain, muscle, bones, kidney, and liver, with the highest concentrations in the prostate and parts of the eye. Semen is particularly rich in zinc, a key factor in prostate gland function and reproductive organ growth.
Zinc homeostasis of the body is mainly controlled by the intestine. Here, SLC39A4, ZIP4 and especially TRPM7 were linked to intestinal zinc uptake essential for postnatal survival.
In humans, the biological roles of zinc are ubiquitous.
It interacts with "a wide range of organic ligands",
and has roles in the metabolism of RNA and DNA, signal transduction, and gene expression. It also regulates apoptosis. A review from 2015 indicated that about 10% of human proteins (~3000) bind zinc,
in addition to hundreds more that transport and traffic zinc; a similar ''in silico'' study in the plant ''Arabidopsis thaliana'' found 2367 zinc-related proteins.
In the brain, zinc is stored in specific synaptic vesicles by glutamatergic neurons and can modulate neuronal excitability.
It plays a key role in synaptic plasticity and so in learning.
Zinc homeostasis also plays a critical role in the functional regulation of the central nervous system.
Dysregulation of zinc homeostasis in the central nervous system that results in excessive synaptic zinc concentrations is believed to induce neurotoxicity through mitochondrial oxidative stress (e.g., by disrupting certain enzymes involved in the electron transport chain, including complex I, complex III, and α-ketoglutarate dehydrogenase), the dysregulation of calcium homeostasis, glutamatergic neuronal excitotoxicity, and interference with intraneuronal signal transduction.
L- and D-histidine facilitate brain zinc uptake. SLC30A3 is the primary Solute carrier family#Solute carrier family 30, zinc transporter involved in cerebral zinc homeostasis.
Enzymes
![Carbonic anhydrase](https://upload.wikimedia.org/wikipedia/commons/4/40/Carbonic_anhydrase.png)
Zinc is an efficient Lewis acid, making it a useful catalytic agent in hydroxylation and other enzymatic reactions.
The metal also has a flexible coordination geometry, which allows proteins using it to rapidly shift protein structure, conformations to perform biological reactions. Two examples of zinc-containing enzymes are carbonic anhydrase and carboxypeptidase, which are vital to the processes of carbon dioxide () regulation and digestion of proteins, respectively.
In vertebrate blood, carbonic anhydrase converts into bicarbonate and the same enzyme transforms the bicarbonate back into for exhalation through the lungs. Without this enzyme, this conversion would occur about one million times slower
at the normal blood pH of 7 or would require a pH of 10 or more.
The non-related β-carbonic anhydrase is required in plants for leaf formation, the synthesis of indole-3-acetic acid, indole acetic acid (auxin) and alcoholic fermentation.
Carboxypeptidase cleaves peptide linkages during digestion of proteins. A coordinate covalent bond is formed between the terminal peptide and a C=O group attached to zinc, which gives the carbon a positive charge. This helps to create a hydrophobic pocket on the enzyme near the zinc, which attracts the non-polar part of the protein being digested.
Signalling
Zinc has been recognized as a messenger, able to activate signalling pathways. Many of these pathways provide the driving force in aberrant cancer growth. They can be targeted through Zinc transporter protein, ZIP transporters.
Other proteins
Zinc serves a purely structural role in zinc fingers, twists and clusters.
Zinc fingers form parts of some transcription factors, which are proteins that recognize DNA sequence, DNA base sequences during the replication and transcription of DNA. Each of the nine or ten ions in a zinc finger helps maintain the finger's structure by coordinately binding to four amino acids in the transcription factor.
In blood plasma, zinc is bound to and transported by albumin (60%, low-affinity) and transferrin (10%).
Because transferrin also transports iron, excessive iron reduces zinc absorption, and vice versa. A similar antagonism exists with copper.
The concentration of zinc in blood plasma stays relatively constant regardless of zinc intake.
Cells in the salivary gland, prostate, immune system, and intestine use Cell signaling, zinc signaling to communicate with other cells.
Zinc may be held in metallothionein reserves within microorganisms or in the intestines or liver of animals.
Metallothionein in intestinal cells is capable of adjusting absorption of zinc by 15–40%.
However, inadequate or excessive zinc intake can be harmful; excess zinc particularly impairs copper absorption because metallothionein absorbs both metals.
The human dopamine transporter contains a affinity (pharmacology), high affinity extracellular zinc binding site which, upon zinc binding, inhibits dopamine reuptake and amplifies amphetamine-induced neurotransmitter efflux, dopamine efflux ''in vitro''.
The human serotonin transporter and norepinephrine transporter do not contain zinc binding sites.
Some EF hand, EF-hand Calcium-binding protein, calcium binding proteins such as S100 protein, S100 or Neuronal calcium sensor-1, NCS-1 are also able to bind zinc ions.
Nutrition
Dietary recommendations
The U.S. Institute of Medicine (IOM) updated Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for zinc in 2001. The current EARs for zinc for women and men ages 14 and up is 6.8 and 9.4 mg/day, respectively. The RDAs are 8 and 11 mg/day. RDAs are higher than EARs so as to identify amounts that will cover people with higher than average requirements. RDA for pregnancy is 11 mg/day. RDA for lactation is 12 mg/day. For infants up to 12 months the RDA is 3 mg/day. For children ages 1–13 years the RDA increases with age from 3 to 8 mg/day. As for safety, the IOM sets Tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. In the case of zinc the adult UL is 40 mg/day (lower for children). Collectively the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes (DRIs).
The European Food Safety Authority (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA, and Average Requirement instead of EAR. AI and UL are defined the same as in the United States. For people ages 18 and older the PRI calculations are complex, as the EFSA has set higher and higher values as the phytate content of the diet increases. For women, PRIs increase from 7.5 to 12.7 mg/day as phytate intake increases from 300 to 1200 mg/day; for men the range is 9.4 to 16.3 mg/day. These PRIs are higher than the U.S. RDAs.
The EFSA reviewed the same safety question and set its UL at 25 mg/day, which is much lower than the U.S. value.
For U.S. food and dietary supplement labeling purposes the amount in a serving is expressed as a percent of Daily Value (%DV). For zinc labeling purposes 100% of the Daily Value was 15 mg, but on May 27, 2016, it was revised to 11 mg.
A table of the old and new adult daily values is provided at Reference Daily Intake.
Dietary intake
![Foodstuff-containing-Zinc](https://upload.wikimedia.org/wikipedia/commons/1/19/Foodstuff-containing-Zinc.jpg)
Animal products such as meat, fish, shellfish, fowl, eggs, and dairy contain zinc. The concentration of zinc in plants varies with the level in the soil. With adequate zinc in the soil, the food plants that contain the most zinc are wheat (germ and bran) and various seeds, including sesame, poppy, alfalfa, celery, and Mustard (condiment), mustard.
Zinc is also found in beans, nut (fruit), nuts, almonds, whole grains, pumpkin seeds, sunflower seeds, and blackcurrant.
Other sources include food fortification, fortified food and dietary supplements in various forms. A 1998 review concluded that zinc oxide, one of the most common supplements in the United States, and zinc carbonate are nearly insoluble and poorly absorbed in the body.
This review cited studies that found lower plasma zinc concentrations in the subjects who consumed zinc oxide and zinc carbonate than in those who took zinc acetate and sulfate salts.
For fortification, however, a 2003 review recommended cereals (containing zinc oxide) as a cheap, stable source that is as easily absorbed as the more expensive forms. A 2005 study found that various compounds of zinc, including oxide and sulfate, did not show statistically significant differences in absorption when added as fortificants to maize tortillas.
Deficiency
Nearly two billion people in the developing world are deficient in zinc. Groups at risk include children in developing countries and elderly with chronic illnesses.
In children, it causes an increase in infection and diarrhea and contributes to the death of about 800,000 children worldwide per year.
The World Health Organization advocates zinc supplementation for severe malnutrition and diarrhea.
Zinc supplements help prevent disease and reduce mortality, especially among children with low birth weight or stunted growth.
However, zinc supplements should not be administered alone, because many in the developing world have several deficiencies, and zinc interacts with other micronutrients. While zinc deficiency is usually due to insufficient dietary intake, it can be associated with malabsorption, acrodermatitis enteropathica, chronic liver disease, chronic renal disease, sickle cell disease, diabetes, malignancy, and other chronic illnesses.
In the United States, a federal survey of food consumption determined that for women and men over the age of 19, average consumption was 9.7 and 14.2 mg/day, respectively. For women, 17% consumed less than the EAR, for men 11%. The percentages below EAR increased with age. The most recent published update of the survey (NHANES 2013–2014) reported lower averages – 9.3 and 13.2 mg/day – again with intake decreasing with age.
Symptoms of mild zinc deficiency are diverse.
Clinical outcomes include depressed growth, diarrhea, impotence and delayed sexual maturation, alopecia, eye and skin lesions, impaired appetite, altered cognition, impaired immune functions, defects in carbohydrate utilization, and reproductive teratogenesis.
Zinc deficiency depresses immunity, but excessive zinc does also.
Despite some concerns,
western vegetarians and vegans do not suffer any more from overt zinc deficiency than meat-eaters. Major plant sources of zinc include cooked dried beans, sea vegetables, fortified cereals, soy foods, nuts, peas, and seeds.
However, phytates in many whole-grains and fibers may interfere with zinc absorption and marginal zinc intake has poorly understood effects. The zinc chelation, chelator phytic acid, phytate, found in seeds and cereal bran, can contribute to zinc malabsorption.
Some evidence suggests that more than the US RDA (8 mg/day for adult women; 11 mg/day for adult men) may be needed in those whose diet is high in phytates, such as some vegetarians.
The European Food Safety Authority (EFSA) guidelines attempt to compensate for this by recommending higher zinc intake when dietary phytate intake is greater.
These considerations must be balanced against the paucity of adequate zinc biomarkers, and the most widely used indicator, plasma zinc, has poor sensitivity and specificity.
Soil remediation
Species of ''Calluna'', ''Erica (plant), Erica'' and ''Vaccinium'' can grow in zinc-metalliferous soils, because translocation of toxic ions is prevented by the action of Ericoid mycorrhiza, ericoid mycorrhizal fungi.
Agriculture
Zinc deficiency appears to be the most common micronutrient deficiency in crop plants; it is particularly common in high-pH soils. Zinc-deficient soil is Tillage, cultivated in the cropland of about half of Turkey and India, a third of China, and most of Western Australia. Substantial responses to zinc fertilization have been reported in these areas.
Plants that grow in soils that are zinc-deficient are more susceptible to disease. Zinc is added to the soil primarily through the weathering of rocks, but humans have added zinc through fossil fuel combustion, mine waste, phosphate fertilizers, pesticide (zinc phosphide), limestone, manure, sewage sludge, and particles from galvanized surfaces. Excess zinc is toxic to plants, although zinc toxicity is far less widespread.
Precautions
Toxicity
Although zinc is an essential requirement for good health, excess zinc can be harmful. Excessive absorption of zinc suppresses copper and iron absorption.
The free zinc ion in solution is highly toxic to plants, invertebrates, and even vertebrate fish. The Free Ion Activity Model is well-established in the literature, and shows that just mole (unit), micromolar amounts of the free ion kills some organisms. A recent example showed 6 micromolar killing 93% of all ''Daphnia'' in water.
The free zinc ion is a powerful Lewis acid up to the point of being corrosive. Stomach acid contains hydrochloric acid, in which metallic zinc dissolves readily to give corrosive zinc chloride. Swallowing a post-1982 American one Cent (United States coin), cent piece (97.5% zinc) can cause damage to the stomach lining through the high solubility of the zinc ion in the acidic stomach.
Evidence shows that people taking 100–300 mg of zinc daily may suffer induced
copper deficiency
Copper deficiency, or hypocupremia, is defined either as insufficient copper to meet the needs of the body, or as a serum copper level below the normal range. Symptoms may include fatigue, decreased red blood cells, early greying of the hair, an ...
. A 2007 trial observed that elderly men taking 80 mg daily were hospitalized for urinary complications more often than those taking a placebo. Levels of 100–300 mg may interfere with the utilization of copper and iron or adversely affect cholesterol.
Zinc in excess of 500 ppm in soil interferes with the plant absorption of other essential metals, such as iron and manganese.
A condition called the zinc shakes or "zinc chills" can be induced by inhalation of zinc fumes while brazing or welding galvanized materials.
Zinc is a common ingredient of denture cream which may contain between 17 and 38 mg of zinc per gram. Disability and even deaths from excessive use of these products have been claimed.
The U.S. Food and Drug Administration (FDA) states that zinc damages nerve receptors in the nose, causing anosmia. Reports of anosmia were also observed in the 1930s when zinc preparations were used in a failed attempt to prevent polio infections. On June 16, 2009, the FDA ordered removal of zinc-based intranasal cold products from store shelves. The FDA said the loss of smell can be life-threatening because people with impaired smell cannot detect leaking gas or smoke, and cannot tell if food has spoiled before they eat it.
Recent research suggests that the topical antimicrobial zinc pyrithione is a potent heat shock response inducer that may impair genomic integrity with induction of Poly ADP ribose polymerase, PARP-dependent energy crisis in cultured human keratinocytes and melanocytes.
Poisoning
In 1982, the United States Mint, US Mint began minting Cent (United States coin), pennies coated in copper but containing primarily zinc. Zinc pennies pose a risk of zinc toxicosis, which can be fatal. One reported case of chronic ingestion of 425 pennies (over 1 kg of zinc) resulted in death due to gastrointestinal bacterial and fungal sepsis. Another patient who ingested 12 grams of zinc showed only
lethargy
Lethargy is a state of tiredness, sleepiness, weariness, fatigue, sluggishness or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to inadequate sleep, overexertion, overwo ...
and
ataxia
Ataxia is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and abnormalities in eye movements. Ataxia is a clinical manifestation indicating dysfunction of ...
(gross lack of coordination of muscle movements). Several other cases have been reported of humans suffering zinc intoxication by the ingestion of zinc coins.
Pennies and other small coins are sometimes ingested by dogs, requiring veterinary removal of the foreign objects. The zinc content of some coins can cause zinc toxicity, commonly fatal in dogs through severe hemolytic anemia and liver or kidney damage; vomiting and diarrhea are possible symptoms. Zinc is highly toxic in parrots and poisoning can often be fatal.
The consumption of fruit juices stored in galvanized cans has resulted in mass parrot poisonings with zinc.
See also
* List of countries by zinc production
* Spelter
* Wet storage stain
* Zinc alloy electroplating
* Metal fume fever
* Piotr Steinkeller
Notes
Citations
Bibliography
*
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External links
Zinc Fact Sheet
from the U.S. National Institutes of Health
History & Etymology of Zinc
Reducing Agents > Zinc
American Zinc Association
Information about the uses and properties of zinc.
ISZB
International Society for Zinc Biology, founded in 2008. An international, nonprofit organization bringing together scientists working on the biological actions of zinc.
Zinc-UK
Founded in 2010 to bring together scientists in the United Kingdom working on zinc.
at ''The Periodic Table of Videos'' (University of Nottingham)
ZincBind
– a database of biological zinc binding sites.
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