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Potassium is a
chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo du ...
with the
symbol A symbol is a mark, sign, or word In linguistics, a word of a spoken language can be defined as the smallest sequence of phonemes that can be uttered in isolation with semantic, objective or pragmatics, practical meaning (linguistics), m ...
K (from Neo-Latin ''
kalium Potassium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

kalium
'') and
atomic number 300px, The Rutherford–Bohr model of the hydrogen atom () or a hydrogen-like ion (). In this model it is an essential feature that the photon energy (or frequency) of the electromagnetic radiation emitted (shown) when an electron jumps from one ...
19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmospheric
oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

oxygen
to form flaky white
potassium peroxide Potassium peroxide is an inorganic compound In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, pr ...

potassium peroxide
in only seconds of exposure. It was first isolated from
potash Potash () includes various mined and manufactured salts In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structu ...
, the ashes of plants, from which its name derives. In the
periodic table The periodic table, also known as the periodic table of (the) chemical elements, is a tabular display of the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is ...

periodic table
, potassium is one of the
alkali metal The alkali metals consist of the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that ...
s, all of which have a single
valence electron In chemistry and physics, a valence electron is an electron in the outer shell Shell may refer to: Architecture and design * Shell (structure)A shell is a type of structural element which is characterized by its geometry, being a three-dimension ...
in the outer electron shell, that is easily removed to create an ion with a positive charge – a
cation An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are u ...
, that combines with
anion An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ...
s to form
salts In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during ...
. Potassium in nature occurs only in ionic salts. Elemental potassium reacts vigorously with water, generating sufficient heat to ignite
hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

hydrogen
emitted in the reaction, and burning with a
lilac ''Syringa vulgaris'', the lilac or common lilac, is a species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often d ...

lilac
- colored flame. It is found dissolved in sea water (which is 0.04% potassium by weight), and occurs in many
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

mineral
s such as
orthoclase Orthoclase, or orthoclase feldspar (endmember An endmember (also end-member or end member) in mineralogy Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical ...

orthoclase
, a common constituent of
granite Granite () is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cool ...

granite
s and other
igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main The three types of rocks, rock types, the others being Sedimentary rock, sedimentary and metamorphic rock, metamorphic. Igneous rock i ...
s. Potassium is chemically very similar to
sodium Sodium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical eleme ...

sodium
, the previous element in group 1 of the periodic table. They have a similar first
ionization energy In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. ...
, which allows for each atom to give up its sole outer electron. It was suspected in 1702 that they were distinct elements that combine with the same
anion An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ...
s to make similar salts, and was proven in 1807 using
electrolysis In chemistry Chemistry is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in ...

electrolysis
. Naturally occurring potassium is composed of three
isotope Isotopes are two or more types of atoms that have the same atomic number 300px, The Rutherford–Bohr model of the hydrogen atom () or a hydrogen-like ion (). In this model it is an essential feature that the photon energy (or frequency) of ...
s, of which

is
radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleus The atomic nucleus is the small, dense region consisting of s and s ...

radioactive
. Traces of are found in all potassium, and it is the most common
radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide A nuclide (or nucleide, from nucleus, also known as nuclear species) is a class of atoms characterized by their number of proton A proton is a subatomic par ...
in the human body. Potassium ions are vital for the functioning of all living cells. The transfer of potassium ions across nerve cell membranes is necessary for normal nerve transmission; potassium deficiency and excess can each result in numerous signs and symptoms, including an abnormal heart rhythm and various
electrocardiographic Electrocardiography is the process of producing an electrocardiogram (ECG or EKG). It is a graph of voltage versus time of the electrical activity of the heart using electrodes placed on the skin. These electrodes detect the small electrical ch ...
abnormalities. Fresh fruits and vegetables are good dietary sources of potassium. The body responds to the influx of dietary potassium, which raises serum potassium levels, with a shift of potassium from outside to inside cells and an increase in potassium excretion by the kidneys. Most industrial applications of potassium exploit the high
solubility In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atom ...

solubility
in water of potassium compounds, such as
potassium Potassium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...
soap Soap is a salt (chemistry), salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, ...

soap
s. Heavy crop production rapidly depletes the soil of potassium, and this can be remedied with agricultural fertilizers containing potassium, accounting for 95% of global potassium chemical production. Greenwood, p. 73


Etymology

The English name for the element ''potassium'' comes from the word ''
potash Potash () includes various mined and manufactured salts In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structu ...
'', which refers to an early method of extracting various potassium salts: placing in a ''pot'' the ''ash'' of burnt wood or tree leaves, adding water, heating, and evaporating the solution. When
Humphry Davy Sir Humphry Davy, 1st Baronet (17 December 177829 May 1829) was a Cornish people, Cornish chemist and inventor who invented the Davy lamp and a very early form of arc lamp. He is also remembered for isolating, by using electricity, a series of ...

Humphry Davy
first isolated the pure element using
electrolysis In chemistry Chemistry is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in ...

electrolysis
in 1807, he named it ''potassium'', which he derived from the word ''potash''. The symbol ''K'' stems from ''kali'', itself from the root word ''
alkali In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo dur ...

alkali
'', which in turn comes from ar, القَلْيَه ''al-qalyah'' 'plant ashes'. In 1797, the German chemist
Martin Klaproth Martin Heinrich Klaproth (1 December 1743 – 1 January 1817) was a German chemist A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin ''alchemist'') is a scientist A scientist is a person who conducts Scie ...

Martin Klaproth
discovered "potash" in the minerals
leucite Leucite is a rock-forming mineral of the feldspathoid group, silica-undersaturated and composed of potassium and aluminium Aluminium (aluminum in American English, American and Canadian English) is a chemical element with the Symbol (che ...

leucite
and
lepidolite Lepidolite is a lilac ''Syringa vulgaris'', the lilac or common lilac, is a species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. ...

lepidolite
, and realized that "potash" was not a product of plant growth but actually contained a new element, which he proposed calling ''kali''. In 1807, Humphry Davy produced the element via electrolysis: in 1809,
Ludwig Wilhelm Gilbert Ludwig Wilhelm Gilbert (12 August 1769 – 7 March 1824) was a Germany, German physicist and chemist, and professor of physics at the University of Leipzig. From 1799-1824 he published the "''Annalen der Physik''", of which Johann Christian Pog ...
proposed the name ''Kalium'' for Davy's "potassium". In 1814, the Swedish chemist advocated the name ''kalium'' for potassium, with the chemical symbol ''K''. The English and French-speaking countries adopted Davy and Gay-Lussac/Thénard's name ''Potassium'', whereas the Germanic countries adopted Gilbert/Klaproth's name ''Kalium''. The "Gold Book" of the
International Union of Pure and Applied Chemistry The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations that represents chemists in individual countries. It is a member of the International Science Council (ISC). IUPAC ...
has designated the official chemical symbol as K.


Properties


Physical

Potassium is the second least dense metal after
lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: the ...

lithium
. It is a soft solid with a low
melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature Temperature ( ) is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy Thermal radiation in visible light can b ...

melting point
, and can be easily cut with a knife. Freshly cut potassium is silvery in appearance, but it begins to tarnish toward gray immediately on exposure to air. Greenwood, p. 76 In a
flame test A flame test is an analytical procedure used in chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure ...

flame test
, potassium and its compounds emit a lilac color with a peak emission wavelength of 766.5 nanometers. Neutral potassium atoms have 19 electrons, one more than the configuration of the
noble gas The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under Standard conditions for temperature and pressure, standard conditions, they are all odorl ...
argon Argon is a with the  Ar and  18. It is in group 18 of the and is a . Argon is the third-most abundant in the , at 0.934% (9340 ). It is more than twice as abundant as (which averages about 4000 ppmv, but varies greatly), 23 time ...

argon
. Because of its low first
ionization energy In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. ...
of 418.8kJ/mol, the potassium atom is much more likely to lose the last electron and acquire a positive charge, although negatively charged
alkalideAn alkalide is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by chemical ...
ions are not impossible. In contrast, the second ionization energy is very high (3052kJ/mol).


Chemical

Potassium reacts with oxygen, water, and carbon dioxide components in air. With oxygen it forms
potassium peroxide Potassium peroxide is an inorganic compound In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, pr ...

potassium peroxide
. With water potassium forms
potassium hydroxide Potassium hydroxide is an inorganic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, ...

potassium hydroxide
. The reaction of potassium with water can be violently
exothermic In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these qu ...

exothermic
, especially since the coproduced
hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

hydrogen
gas can ignite. Because of this, potassium and the liquid sodium-potassium () alloy are potent
desiccant A desiccant is a hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal ...
s, although they are no longer used as such.


Compounds

Three oxides of potassium are well studied:
potassium oxide Potassium oxide (K O) is an ionic compound Compound may refer to: Architecture and built environments * Compound (enclosure), a cluster of buildings having a shared purpose, usually inside a fence or wall ** Compound (fortification), a version of ...
(K2O),
potassium peroxide Potassium peroxide is an inorganic compound In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, pr ...

potassium peroxide
(K2O2), and
potassium superoxide Potassium superoxide is an inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. However, the distinction is not clearly def ...

potassium superoxide
(KO2). The binary potassium-oxygen binary compounds react with water forming
potassium hydroxide Potassium hydroxide is an inorganic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, ...

potassium hydroxide
. Potassium hydroxide (KOH) is a strong base. Illustrating its hydrophilic character, as much as 1.21 kg of KOH can dissolve in a single liter of water. Anhydrous KOH is rarely encountered. KOH reacts readily with carbon dioxide to produce
potassium carbonate Potassium carbonate is the inorganic compound with the formula K2 CO3. It is a white salt, which is soluble in water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color o ...

potassium carbonate
and in principle could be used to remove traces of the gas from air. Like the closely related sodium hydroxide, potassium hydroxide reacts with fats to produce
soap Soap is a salt (chemistry), salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, ...

soap
s. In general, potassium compounds are ionic and, owing to the high hydration energy of the ion, have excellent water solubility. The main species in water solution are the aquated complexes where n = 6 and 7.Lincoln, S. F.; Richens, D. T. and Sykes, A. G. "Metal Aqua Ions" in J. A. McCleverty and T. J. Meyer (eds.
''Comprehensive Coordination Chemistry II''
Vol. 1, pp. 515–555, .
Potassium heptafluorotantalate is an intermediate in the purification of tantalum from the otherwise persistent contaminant of niobium.
Organopotassium compoundOrganosodium chemistry is the chemistry of organometallic compounds containing a carbon to sodium chemical bond. The application of organosodium compounds in chemistry is limited in part due to competition from organolithium compounds, which are com ...
s illustrate nonionic compounds of potassium. They feature highly polar covalent K---C bonds. Examples include . Potassium intercalates into
graphite Graphite (), archaically referred to as plumbago, is a Crystallinity, crystalline form of the element carbon with its atoms arranged in a Hexagonal crystal system, hexagonal structure. It occurs naturally in this form and is the most stable for ...

graphite
to give a variety of compounds, including
KC8 Graphite intercalation compounds (GICs) are complex materials having a formula CXm where the ion Xn+ or Xn− is inserted (intercalation (chemistry), intercalated) between the oppositely charged carbon layers. Typically m is much less than 1. Th ...
.


Isotopes

There are 25 known
isotope Isotopes are two or more types of atoms that have the same atomic number 300px, The Rutherford–Bohr model of the hydrogen atom () or a hydrogen-like ion (). In this model it is an essential feature that the photon energy (or frequency) of ...
s of potassium, three of which occur naturally: (93.3%), (0.0117%), and (6.7%). Naturally occurring has a
half-life Half-life (symbol ''t''1⁄2) is the time required for a quantity to reduce to half of its initial value. The term is commonly used in nuclear physics Nuclear physics is the field of physics Physics is the natural science that studies ...
of 1.250×109 years. It decays to stable by
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 An atom is the smallest unit of ordinary matter In classical physics ...

electron capture
or
positron emission Positron emission, beta plus decay, or β+ decay is a subtype of radioactive decay Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic ...
(11.2%) or to stable by
beta decay In , beta decay (''β''-decay) is a type of in which a (fast energetic or ) is emitted from an , transforming the original to an of that nuclide. For example, beta decay of a transforms it into a by the emission of an electron accompanie ...

beta decay
(88.8%). The decay of to is the basis of a common method for dating rocks. The conventional K-Ar dating method depends on the assumption that the rocks contained no argon at the time of formation and that all the subsequent radiogenic argon () was quantitatively retained.
Mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

Mineral
s are dated by measurement of the concentration of potassium and the amount of radiogenic that has accumulated. The minerals best suited for dating include
biotite Biotite is a common group of phyllosilicate Silicate minerals are rock-forming mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science conce ...

biotite
,
muscovite Muscovite (also known as common mica, isinglass, or potash mica) is a hydrated phyllosilicate Silicate minerals are rock-forming mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'' ...

muscovite
, metamorphic
hornblende Hornblende is a complex inosilicate series of mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock ...

hornblende
, and volcanic
feldspar Feldspars are a group of rock-forming aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity ...
; whole rock samples from volcanic flows and shallow instrusives can also be dated if they are unaltered. Apart from dating, potassium isotopes have been used as tracers in studies of
weathering Weathering is the deterioration of Rock (geology), rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little o ...
and for
nutrient cycling A nutrient cycle (or ecological recycling) is the movement and exchange of organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ (anatomy), organ Chemistry * Org ...
studies because potassium is a
macronutrient A nutrient is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition * Matter, anything that has mass and ta ...
required for
life Life is a characteristic that distinguishes physical entities A bubble of exhaled gas in water In common usage and classical mechanics, a physical object or physical body (or simply an object or body) is a collection of matter within a ...

life
. occurs in natural potassium (and thus in some commercial salt substitutes) in sufficient quantity that large bags of those substitutes can be used as a radioactive source for classroom demonstrations. is the radioisotope with the largest abundance in the body. In healthy animals and people, represents the largest source of radioactivity, greater even than . In a human body of 70kg mass, about 4,400 nuclei of decay per second. The activity of natural potassium is 31 Bq/g.


Cosmic formation and distribution

Potassium is formed in
supernova A supernova ( plural: supernovae or supernovas, abbreviations: SN and SNe) is a powerful and luminous stellar explosion. This transient astronomical event occurs during the last stellar evolution, evolutionary stages of a massive star or when a ...

supernova
e by
nucleosynthesis Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons (protons and neutrons) and nuclei. According to current theories, the first nuclei were formed a few minutes after the Big Bang, through nuclear reactions in ...
from lighter atoms. Potassium is principally created in Type II supernovae via an explosive oxygen-burning process. is also formed in
s-process The slow neutron-capture process, or ''s''-process, is a series of reactions in nuclear astrophysics that occur in stars, particularly AGB stars. The ''s''-process is responsible for the creation ( nucleosynthesis) of approximately half the atomi ...
nucleosynthesis and the
neon burning process Neon is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior ...
. Potassium is the 20th most abundant element in the solar system and the 17th most abundant element by weight in the Earth. It makes up about 2.6% of the weight of the
earth's crust 350px, Plates in the crust of Earth Earth's crust is a thin shell on the outside of Earth, accounting for less than 1% of Earth's volume. It is the top component of the lithosphere, a division of Earth's layers that includes the Crust (geology), ...
and is the seventh most abundant element in the crust. The potassium concentration in seawater is 0.39g/L (0.039 wt/v%), about one twenty-seventh the concentration of sodium.


Potash

Potash is primarily a mixture of potassium salts because plants have little or no sodium content, and the rest of a plant's major mineral content consists of calcium salts of relatively low solubility in water. While potash has been used since ancient times, its composition was not understood.
Georg Ernst Stahl Georg Ernst Stahl (22 October 1659 – 24 May 1734) was a German chemist, physician A physician (American English), medical practitioner (English in the Commonwealth of Nations, Commonwealth English), medical doctor, or simply doctor, is a ...

Georg Ernst Stahl
obtained experimental evidence that led him to suggest the fundamental difference of sodium and potassium salts in 1702, and was able to prove this difference in 1736. The exact chemical composition of potassium and sodium compounds, and the status as chemical element of potassium and sodium, was not known then, and thus
Antoine Lavoisier Antoine-Laurent de Lavoisier ( , ,; 26 August 17438 May 1794), When reduced without charcoal, it gave off an air which supported respiration and combustion in an enhanced way. He concluded that this was just a pure form of common air and t ...

Antoine Lavoisier
did not include the alkali in his list of chemical elements in 1789. For a long time the only significant applications for potash were the production of glass, bleach, soap and
gunpowder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). The ...
as potassium nitrate. Potassium soaps from animal fats and vegetable oils were especially prized because they tend to be more water-soluble and of softer texture, and are therefore known as soft
soap Soap is a salt (chemistry), salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, ...

soap
s. The discovery by
Justus Liebig Justus von Liebig (12 May 1803 – 18 April 1873) was a German scientist who made major contributions to agricultural and , and is considered one of the principal founders of . As a professor at the , he devised the modern laboratory-oriented ...
in 1840 that potassium is a necessary element for plants and that most types of soil lack potassium caused a steep rise in demand for potassium salts. Wood-ash from fir trees was initially used as a potassium salt source for fertilizer, but, with the discovery in 1868 of mineral deposits containing
potassium chloride Potassium chloride (KCl, or potassium salt) is a metal halide Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. Covalently bonded metal halides may be discrete m ...

potassium chloride
near
Staßfurt Staßfurt (Stassfurt) () is a town in the Salzlandkreis district, in Saxony-Anhalt, Germany. It is situated on both sides of the river Bode River, Bode, approximately northeast of Aschersleben, and south of Magdeburg. Pop. (2005) 23,538. It was ...
, Germany, the production of potassium-containing fertilizers began at an industrial scale. Other potash deposits were discovered, and by the 1960s Canada became the dominant producer.


Metal

Potassium ''metal'' was first isolated in 1807 by Humphry Davy, who derived it by electrolysis of molten KOH with the newly discovered
voltaic pile The voltaic pile was the first electrical battery A battery is a device consisting of one or more electrochemical cell An electrochemical cell is a device capable of either generating electrical energy from chemical reaction A che ...

voltaic pile
. Potassium was the first metal that was isolated by electrolysis. Later in the same year, Davy reported extraction of the metal
sodium Sodium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical eleme ...

sodium
from a mineral derivative ( caustic soda, NaOH, or lye) rather than a plant salt, by a similar technique, demonstrating that the elements, and thus the salts, are different. Although the production of potassium and sodium metal should have shown that both are elements, it took some time before this view was universally accepted. Because of the sensitivity of potassium to water and air,
air-free techniqueAir-free techniques refer to a range of manipulations in the chemistry laboratory for the handling of Compound (chemistry), compounds that are air-sensitive. These techniques prevent the compounds from reacting with components of air, usually water a ...
s are normally employed for handling the element. It is unreactive toward nitrogen and saturated hydrocarbons such as mineral oil or
kerosene Kerosene, paraffin, or lamp oil is a combustible , Germany ) , image_map = , map_caption = , map_width = 250px , capital = Berlin , coordinates = , largest_city = capital , languages_type = Official language , languages = G ...

kerosene
. It readily dissolves in liquid
ammonia Ammonia is a chemical compound, compound of nitrogen and hydrogen with the chemical formula, formula NH3. A Binary compounds of hydrogen, stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct ch ...

ammonia
, up to 480 g per 1000 g of ammonia at 0°C. Depending on the concentration, the ammonia solutions are blue to yellow, and their electrical conductivity is similar to that of liquid metals. Potassium slowly reacts with ammonia to form , but this reaction is accelerated by minute amounts of transition metal salts. Burkhardt, p. 32 Because it can reduce the
salt Salt is a mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure fo ...
s to the metal, potassium is often used as the reductant in the preparation of finely divided metals from their salts by the Rieke method. Illustrative is the preparation of magnesium: : + 2 K → Mg + 2 KCl


Geology

Elemental potassium does not occur in nature because of its high reactivity. It reacts violently with water (see section Precautions below) and also reacts with oxygen.
Orthoclase Orthoclase, or orthoclase feldspar (endmember An endmember (also end-member or end member) in mineralogy Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical ...

Orthoclase
(potassium feldspar) is a common rock-forming mineral.
Granite Granite () is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cool ...

Granite
for example contains 5% potassium, which is well above the average in the Earth's crust.
Sylvite Sylvite, or sylvine, is potassium chloride Potassium chloride (KCl, or potassium salt) is a metal halide Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. Cova ...

Sylvite
(KCl),
carnallite Carnallite (also carnalite) is an mineral, a hydrated with formula KMgCl3·6(H2O). It is variably colored yellow to white, reddish, and sometimes colorless or blue. It is usually massive to fibrous with rare pseudohexagonal crystals. The miner ...
,
kainite Kainite ( or ) (KMg(SO4)Cl·3H2O) is an evaporite evaporated from the Dead Sea, Israel Evaporite () is the term for a water-soluble mineral sediment Sediment is a naturally occurring material that is broken down by processes of weathering ...

kainite
and
langbeinite Langbeinite is a potassium Potassium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of ...
are the minerals found in large evaporite deposits worldwide. The deposits often show layers starting with the least soluble at the bottom and the most soluble on top. Deposits of niter (potassium nitrate) are formed by decomposition of organic material in contact with atmosphere, mostly in caves; because of the good water solubility of niter the formation of larger deposits requires special environmental conditions.


Biological role

Potassium is the eighth or ninth most common element by mass (0.2%) in the human body, so that a 60kg adult contains a total of about 120g of potassium. The Composition of the human body, body has about as much potassium as sulfur and chlorine, and only calcium and phosphorus are more abundant (with the exception of the ubiquitous CHON elements). Potassium ions are present in a wide variety of proteins and enzymes.


Biochemical function

Potassium levels influence multiple physiological processes, including * resting cellular-membrane potential and the propagation of action potentials in neuronal, muscular, and cardiac tissue. Due to the electrostatic and chemical properties, ions are larger than ions, and ion channels and pumps in cell membranes can differentiate between the two ions, actively pumping or passively passing one of the two ions while blocking the other. * hormone secretion and action * vascular tone * systemic blood pressure control * gastrointestinal motility * acid–base homeostasis * glucose and insulin metabolism * mineralocorticoid action * renal concentrating ability * fluid and electrolyte balance


Homeostasis

Potassium homeostasis denotes the maintenance of the total body potassium content, plasma potassium level, and the ratio of the intracellular to extracellular potassium concentrations within narrow limits, in the face of pulsatile intake (meals), obligatory renal excretion, and shifts between intracellular and extracellular compartments.


Plasma levels

Plasma potassium is normally kept at 3.5 to 5.0 millimoles (mmol) [or milliequivalents (mEq)] per liter by multiple mechanisms. Levels outside this range are associated with an increasing rate of death from multiple causes, and some cardiac, kidney, and lung diseases progress more rapidly if serum potassium levels are not maintained within the normal range. An average meal of 40–50mmol presents the body with more potassium than is present in all plasma (20–25mmol). However, this surge causes the plasma potassium to rise only 10% at most as a result of prompt and efficient clearance by both renal and extra-renal mechanisms. Hypokalemia, a deficiency of potassium in the plasma, can be fatal if severe. Common causes are increased gastrointestinal loss (vomiting, diarrhea), and increased renal loss (polyuria, diuresis). Deficiency symptoms include muscle weakness, paralytic ileus, ECG abnormalities, decreased reflex response; and in severe cases, respiratory paralysis, alkalosis, and cardiac arrhythmia.


Control mechanisms

Potassium content in the plasma is tightly controlled by four basic mechanisms, which have various names and classifications. The four are 1) a reactive negative-feedback system, 2) a reactive feed-forward system, 3) a predictive or circadian system, and 4) an internal or cell membrane transport system. Collectively, the first three are sometimes termed the "external potassium homeostasis system"; and the first two, the "reactive potassium homeostasis system". * The reactive negative-feedback system refers to the system that induces renal secretion of potassium in response to a rise in the plasma potassium (potassium ingestion, shift out of cells, or intravenous infusion.) * The reactive feed-forward system refers to an incompletely understood system that induces renal potassium secretion in response to potassium ingestion prior to any rise in the plasma potassium. This is probably initiated by gut cell potassium receptors that detect ingested potassium and trigger vagal afferent nerve fiber, afferent signals to the pituitary gland. * The predictive or circadian system increases renal secretion of potassium during mealtime hours (e.g. daytime for humans, nighttime for rodents) independent of the presence, amount, or absence of potassium ingestion. It is mediated by a circadian oscillator in the suprachiasmatic nucleus of the brain (central clock), which causes the kidney (peripheral clock) to secrete potassium in this rhythmic circadian fashion. * The ion transport system moves potassium across the cell membrane using two mechanisms. One is active and pumps sodium out of, and potassium into, the cell. The other is passive and allows potassium to leak out of the cell. Potassium and sodium cations influence fluid distribution between intracellular and extracellular compartments by osmotic forces. The movement of potassium and sodium through the cell membrane is mediated by the Na+/K+-ATPase pump. This Ion transporter, ion pump uses Adenosine triphosphate, ATP to pump three sodium ions out of the cell and two potassium ions into the cell, creating an electrochemical gradient and electromotive force across the cell membrane. The highly selective potassium ion channels (which are tetramers) are crucial for Hyperpolarization (biology), hyperpolarization inside neurons after an action potential is triggered, to cite one example. The most recently discovered potassium ion channel is KirBac3.1, which makes a total of five potassium ion channels (KcsA, KirBac1.1, KirBac3.1, KvAP, and MthK) with a determined structure. All five are from prokaryotic species.


Renal filtration, reabsorption, and excretion

Renal handling of potassium is closely connected to sodium handling. Potassium is the major cation (positive ion) inside animal cells [150mmol/L, (4.8g)], while sodium is the major cation of extracellular fluid [150mmol/L, (3.345g)]. In the kidneys, about 180liters of plasma is filtered through the glomeruli and into the renal tubules per day. This filtering involves about 600g of sodium and 33g of potassium. Since only 1–10g of sodium and 1–4g of potassium are likely to be replaced by diet, renal filtering must efficiently reabsorb the remainder from the plasma. Sodium is reabsorbed to maintain extracellular volume, osmotic pressure, and serum sodium concentration within narrow limits. Potassium is reabsorbed to maintain serum potassium concentration within narrow limits. Sodium pumps in the renal tubules operate to reabsorb sodium. Potassium must be conserved, but because the amount of potassium in the blood plasma is very small and the pool of potassium in the cells is about 30 times as large, the situation is not so critical for potassium. Since potassium is moved passively in counter flow to sodium in response to an apparent (but not actual) Donnan equilibrium, the urine can never sink below the concentration of potassium in serum except sometimes by actively excreting water at the end of the processing. Potassium is excreted twice and reabsorbed three times before the urine reaches the collecting tubules. At that point, urine usually has about the same potassium concentration as plasma. At the end of the processing, potassium is secreted one more time if the serum levels are too high. With no potassium intake, it is excreted at about 200mg per day until, in about a week, potassium in the serum declines to a mildly deficient level of 3.0–3.5mmol/L. If potassium is still withheld, the concentration continues to fall until a severe deficiency causes eventual death. The potassium moves passively through pores in the cell membrane. When ions move through Ion transporters (pumps) there is a gate in the pumps on both sides of the cell membrane and only one gate can be open at once. As a result, approximately 100 ions are forced through per second. Ion channel have only one gate, and there only one kind of ion can stream through, at 10 million to 100 million ions per second. Calcium is required to open the pores, although calcium may work in reverse by blocking at least one of the pores. Carbonyl groups inside the pore on the amino acids mimic the water hydration that takes place in water solution by the nature of the electrostatic charges on four carbonyl groups inside the pore.


Nutrition


Dietary recommendations

The U.S. National Academy of Medicine (NAM), on behalf of both the U.S. and Canada, sets Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs), or Adequate Intakes (AIs) for when there is not sufficient information to set EARs and RDAs. Collectively the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes. For both males and females under 9 years of age, the AIs for potassium are: 400mg of potassium for 0-6-month-old infants, 860mg of potassium for 7-12-month-old infants, 2,000mg of potassium for 1-3-year-old children, and 2,300mg of potassium for 4-8-year-old children. For males 9 years of age and older, the AIs for potassium are: 2,500mg of potassium for 9-13-year-old males, 3,000mg of potassium for 14-18-year-old males, and 3,400mg for males that are 19 years of age and older. For females 9 years of age and older, the AIs for potassium are: 2,300mg of potassium for 9-18-year-old females, and 2,600mg of potassium for females that are 19 years of age and older. For pregnant and lactating females, the AIs for potassium are: 2,600mg of potassium for 14-18-year-old pregnant females, 2,900mg for pregnant females that are 19 years of age and older; furthermore, 2,500mg of potassium for 14-18-year-old lactating females, and 2,800mg for lactating females that are 19 years of age and older. As for safety, the NAM also sets tolerable upper intake levels (ULs) for vitamins and minerals, but for potassium the evidence was insufficient, so no UL was established. As of 2004, most Americans adults consume less than 3,000mg. Likewise, in the European Union, in particular in Germany and Italy, insufficient potassium intake is somewhat common. The National Health Service, British National Health Service recommends a similar intake, saying that adults need 3,500mg per day and that excess amounts may cause health problems such as stomach pain and diarrhoea. Previously the Adequate Intake for adults was set at 4,700 mg per day. In 2019, the National Academies of Sciences, Engineering, and Medicine revised the AI for potassium to 2,600 mg/day for females 19 years and older and 3,400 mg/day for males 19 years and older.


Food sources

Potassium is present in all fruits, vegetables, meat and fish. Foods with high potassium concentrations include Yam (vegetable), yam, parsley, dried apricots, milk, chocolate, all nut (fruit), nuts (especially almonds and pistachios), potatoes, bamboo shoots, bananas, avocados, coconut water, soybeans, and bran. The United States Department of Agriculture, USDA lists tomato paste, orange juice, beet greens, white beans, potatoes, Cooking banana, plantains, bananas, apricots, and many other dietary sources of potassium, ranked in descending order according to potassium content. A day's worth of potassium is in 5 plantains or 11 bananas.


Deficient intake

Diets low in potassium can lead to hypertension and hypokalemia.


Supplementation

Supplements of potassium are most widely used in conjunction with diuretics that block reabsorption of sodium and water upstream from the distal tubule (thiazides and loop diuretics), because this promotes increased distal tubular potassium secretion, with resultant increased potassium excretion. A variety of prescription and over-the counter supplements are available. Potassium chloride may be dissolved in water, but the salty/bitter taste make liquid supplements unpalatable. Typical doses range from 10mmol (400mg), to 20mmol (800mg). Potassium is also available in tablets or capsules, which are formulated to allow potassium to leach slowly out of a matrix, since very high concentrations of potassium ion that occur adjacent to a solid tablet can injure the gastric or intestinal mucosa. For this reason, non-prescription potassium pills are limited by law in the US to a maximum of 99mg of potassium. Since the kidneys are the site of potassium excretion, individuals with impaired kidney function are at risk for hyperkalemia if dietary potassium and supplements are not restricted. The more severe the impairment, the more severe is the restriction necessary to avoid hyperkalemia. A meta-analysis concluded that a 1640mg increase in the daily intake of potassium was associated with a 21% lower risk of stroke. Potassium chloride and potassium bicarbonate may be useful to control mild hypertension. In 2017, potassium was the 37th most commonly prescribed medication in the United States, with more than 19 million prescriptions.


Detection by taste buds

Potassium can be detected by taste because it triggers three of the five types of taste sensations, according to concentration. Dilute solutions of potassium ions taste sweet, allowing moderate concentrations in milk and juices, while higher concentrations become increasingly bitter/alkaline, and finally also salty to the taste. The combined bitterness and saltiness of high-potassium solutions makes high-dose potassium supplementation by liquid drinks a palatability challenge.


Commercial production


Mining

Potassium salts such as
carnallite Carnallite (also carnalite) is an mineral, a hydrated with formula KMgCl3·6(H2O). It is variably colored yellow to white, reddish, and sometimes colorless or blue. It is usually massive to fibrous with rare pseudohexagonal crystals. The miner ...
,
langbeinite Langbeinite is a potassium Potassium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of ...
, polyhalite, and sylvite form extensive evaporite deposits in ancient lake bottoms and seabeds, making extraction of potassium salts in these environments commercially viable. The principal source of potassium –
potash Potash () includes various mined and manufactured salts In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structu ...
– is mined in Canada, Russia, Belarus, Kazakhstan, Germany, Israel, United States, Jordan, and other places around the world. The first mined deposits were located near Staßfurt, Germany, but the deposits span from Great Britain over Germany into Poland. They are located in the Zechstein and were deposited in the Middle to Late Permian. The largest deposits ever found lie below the surface of the Canadian province of Saskatchewan. The deposits are located in the Elk Point Group produced in the Middle Devonian. Saskatchewan, where several large mines have operated since the 1960s pioneered the technique of freezing of wet sands (the Blairmore formation) to drive mine shafts through them. The main potash mining company in Saskatchewan until its merge was the Potash Corporation of Saskatchewan, now Nutrien. The water of the Dead Sea is used by Israel and Jordan as a source of potash, while the concentration in normal oceans is too low for commercial production at current prices.


Chemical extraction

Several methods are used to separate potassium salts from sodium and magnesium compounds. The most-used method is fractional precipitation using the solubility differences of the salts. Electrostatic separation of the ground salt mixture is also used in some mines. The resulting sodium and magnesium waste is either stored underground or piled up in slag heaps. Most of the mined potassium mineral ends up as
potassium chloride Potassium chloride (KCl, or potassium salt) is a metal halide Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. Covalently bonded metal halides may be discrete m ...

potassium chloride
after processing. The mineral industry refers to potassium chloride either as potash, muriate of potash, or simply MOP. Pure potassium metal can be isolated by
electrolysis In chemistry Chemistry is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in ...

electrolysis
of its potassium hydroxide, hydroxide in a process that has changed little since it was first used by Humphry Davy in 1807. Although the electrolysis process was developed and used in industrial scale in the 1920s, the thermal method by reacting sodium with
potassium chloride Potassium chloride (KCl, or potassium salt) is a metal halide Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. Covalently bonded metal halides may be discrete m ...

potassium chloride
in a chemical equilibrium reaction became the dominant method in the 1950s. The production of NaK, sodium potassium alloys is accomplished by changing the reaction time and the amount of sodium used in the reaction. The Griesheimer process employing the reaction of potassium fluoride with calcium carbide was also used to produce potassium. :Na + KCl → NaCl + K (Thermal method) :2 KF + → 2 K + + 2 C (Griesheimer process) reagent, Reagent-grade potassium metal costs about $10.00/pound (mass), pound ($22/kg) in 2010 when purchased by the tonne. Lower purity metal is considerably cheaper. The market is volatile because long-term storage of the metal is difficult. It must be stored in a dry inert gas atmosphere or anhydrous mineral oil to prevent the formation of a surface layer of
potassium superoxide Potassium superoxide is an inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. However, the distinction is not clearly def ...

potassium superoxide
, a pressure-sensitive explosive that Detonation, detonates when scratched. The resulting explosion often starts a fire difficult to extinguish.


Cation identification

Potassium is now quantified by ionization techniques, but at one time it was quantitated by gravimetric analysis. Reagents used to precipitate potassium salts include sodium tetraphenylborate, hexachloroplatinic acid, and sodium cobaltinitrite into respectively potassium tetraphenylborate, potassium hexachloroplatinate, and potassium cobaltinitrite. The reaction with sodium cobaltinitrite is illustrative: : 3K+ + Na3[Co(NO2)6] → K3[Co(NO2)6] + 3Na+ The potassium cobaltinitrite is obtained as a yellow solid.


Commercial uses


Fertilizer

Potassium ions are an essential component of plant nutrition and are found in most soil types. They are used as a fertilizer in agriculture, horticulture, and hydroponic culture in the form of potassium chloride, chloride (KCl), potassium sulfate, sulfate (), or potassium nitrate, nitrate (), representing the 'K' labeling of fertilizer, in 'NPK'. Agricultural fertilizers consume 95% of global potassium chemical production, and about 90% of this potassium is supplied as KCl. The potassium content of most plants ranges from 0.5% to 2% of the harvested weight of crops, conventionally expressed as amount of . Modern high-Crop yield, yield agriculture depends upon fertilizers to replace the potassium lost at harvest. Most agricultural fertilizers contain potassium chloride, while potassium sulfate is used for chloride-sensitive crops or crops needing higher sulfur content. The sulfate is produced mostly by decomposition of the complex minerals
kainite Kainite ( or ) (KMg(SO4)Cl·3H2O) is an evaporite evaporated from the Dead Sea, Israel Evaporite () is the term for a water-soluble mineral sediment Sediment is a naturally occurring material that is broken down by processes of weathering ...

kainite
() and
langbeinite Langbeinite is a potassium Potassium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of ...
(). Only a very few fertilizers contain potassium nitrate. In 2005, about 93% of world potassium production was consumed by the fertilizer industry. Furthermore, potassium can play a key role in nutrient cycling by controlling litter composition.


Medical use

Potassium, in the form of
potassium chloride Potassium chloride (KCl, or potassium salt) is a metal halide Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. Covalently bonded metal halides may be discrete m ...

potassium chloride
is used as a medication to treat and prevent low blood potassium. Low blood potassium may occur due to vomiting, diarrhea, or certain medications. It is given by intravenous infusion, slow injection into a vein or by mouth.


Food additives

Potassium sodium tartrate (, Rochelle salt) is a main constituent of some varieties of baking powder; it is also used in the silvering of mirrors. Potassium bromate () is a strong oxidizer (E924), used to improve dough strength and rise height. Potassium bisulfite () is used as a food preservative, for example in wine and beer-making (but not in meats). It is also used to bleach textiles and straw, and in the tanning of leathers.


Industrial

Major potassium chemicals are potassium hydroxide, potassium carbonate, potassium sulfate, and potassium chloride. Megatons of these compounds are produced annually. Potassium hydroxide is a strong base, which is used in industry to neutralize strong and weak acids, to control pH and to manufacture potassium salt (chemistry), salts. It is also used to saponification, saponify fats and oils, in industrial cleaners, and in hydrolysis reactions, for example of esters. Potassium nitrate () or saltpeter is obtained from natural sources such as guano and evaporites or manufactured via the Haber process; it is the oxidant in
gunpowder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). The ...
(black powder) and an important agricultural fertilizer. Potassium cyanide (KCN) is used industrially to dissolve copper and precious metals, in particular silver and gold, by forming complex (chemistry), complexes. Its applications include gold mining, electroplating, and electroforming of these metals; it is also used in organic synthesis to make nitriles. Potassium carbonate ( or potash) is used in the manufacture of glass, soap, color TV tubes, fluorescent lamps, textile dyes and pigments. Potassium permanganate () is an oxidizing, bleaching and purification substance and is used for production of saccharin. Potassium chlorate () is added to matches and explosives. Potassium bromide (KBr) was formerly used as a sedative and in photography. Potassium chromate () is used in inks, dyes, stains (bright yellowish-red color); in explosives and fireworks; in the tanning of leather, in fly paper and safety matches, but all these uses are due to the chemistry of the chromate ion, rather than the potassium ion.


Niche uses

There are thousands of uses of various potassium compounds. One example is
potassium superoxide Potassium superoxide is an inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. However, the distinction is not clearly def ...

potassium superoxide
, , an orange solid that acts as a portable source of oxygen and a carbon dioxide absorber. It is widely used in Rebreather#Rebreathers using an absorbent that releases oxygen, respiration systems in mines, submarines and spacecraft as it takes less volume than the gaseous oxygen. : 4 + 2 → 2 + 3 Another example is potassium cobaltinitrite, , which is used as artist's pigment under the name of Aureolin or Cobalt Yellow. The stable isotopes of potassium can be Laser cooling, laser cooled and used to probe fundamental and Quantum technology, technological problems in Quantum mechanics, quantum physics. The two bosonic isotopes possess convenient Feshbach resonances to enable studies requiring tunable interactions, while 40K is one of only two stable fermions amongst the alkali metals.


Laboratory uses

An alloy of sodium and potassium, is a liquid used as a heat-transfer medium and a
desiccant A desiccant is a hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal ...
for producing air-free technique, dry and air-free solvents. It can also be used in reactive distillation. The ternary alloy of 12% Na, 47% K and 41% Cs has the lowest melting point of −78°C of any metallic compound. Metallic potassium is used in several types of magnetometers.


Precautions

Potassium metal can react violently with water producing
potassium hydroxide Potassium hydroxide is an inorganic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, ...

potassium hydroxide
(KOH) and
hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

hydrogen
gas. :2 K (s) + 2 (l) → 2 KOH (aq) + ↑ (g) This reaction is exothermic and releases sufficient heat to ignite the resulting hydrogen in the presence of oxygen. Finely powdered potassium ignites in air at room temperature. The bulk metal ignites in air if heated. Because its density is 0.89g/cm3, burning potassium floats in water that exposes it to atmospheric oxygen. Many common fire extinguishing agents, including water, either are ineffective or make a potassium fire worse. Nitrogen,
argon Argon is a with the  Ar and  18. It is in group 18 of the and is a . Argon is the third-most abundant in the , at 0.934% (9340 ). It is more than twice as abundant as (which averages about 4000 ppmv, but varies greatly), 23 time ...

argon
, sodium chloride (table salt), sodium carbonate (soda ash), and silicon dioxide (sand) are effective if they are dry. Some Fire extinguisher, Class D dry powder extinguishers designed for metal fires are also effective. These agents deprive the fire of oxygen and cool the potassium metal. During storage, potassium forms peroxides and superoxides. These peroxides may react violently with organic compounds such as oils. Both peroxides and superoxides may react explosively with metallic potassium. Because potassium reacts with water vapor in the air, it is usually stored under anhydrous mineral oil or kerosene. Unlike lithium and sodium, however, potassium should not be stored under oil for longer than six months, unless in an inert (oxygen free) atmosphere, or under vacuum. After prolonged storage in air dangerous shock-sensitive peroxides can form on the metal and under the lid of the container, and can detonate upon opening. Ingestion of large amounts of potassium compounds can lead to hyperkalemia, strongly influencing the cardiovascular system. Potassium chloride is used in the United States for lethal injection executions.


See also


References


Bibliography

* * * *
National Nutrient Database
at USDA Website


External links

* {{Authority control Potassium, Alkali metals Articles containing video clips Biology and pharmacology of chemical elements Chemical elements Desiccants Dietary minerals Reducing agents Chemical elements with body-centered cubic structure