Potassium

Potassium

Overview
Potassium is the chemical element
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...

 with the symbol K (from Neo-Latin kalium) and atomic number
Atomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...

 19. Elemental potassium is a soft silvery-white alkali metal
Alkali metal
The alkali metals are a series of chemical elements in the periodic table. In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, along with hydrogen. The alkali metals are lithium , sodium , potassium , rubidium , caesium , and francium...

 that oxidizes
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

 rapidly in air
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...

 and is very reactive with water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

, generating sufficient heat to ignite the hydrogen emitted in the reaction.

Potassium and sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 are chemically very similar. For this reason it took a long time before their salts were differentiated.
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Encyclopedia
Potassium is the chemical element
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...

 with the symbol K (from Neo-Latin kalium) and atomic number
Atomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...

 19. Elemental potassium is a soft silvery-white alkali metal
Alkali metal
The alkali metals are a series of chemical elements in the periodic table. In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, along with hydrogen. The alkali metals are lithium , sodium , potassium , rubidium , caesium , and francium...

 that oxidizes
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

 rapidly in air
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...

 and is very reactive with water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

, generating sufficient heat to ignite the hydrogen emitted in the reaction.

Potassium and sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 are chemically very similar. For this reason it took a long time before their salts were differentiated. The existence of multiple elements in their salts was suspected from 1702, and this was proven in 1807 when potassium and sodium were individually isolated from different salts by electrolysis
Electrolysis
In chemistry and manufacturing, electrolysis is a method of using a direct electric current to drive an otherwise non-spontaneous chemical reaction...

. Potassium in nature occurs only in ionic salts. As such, it is found dissolved in seawater
Seawater
Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...

 (which is 0.04% potassium by weight), and is part of many mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

s.

Most industrial chemical applications of potassium employ the relatively high solubility in water of potassium compounds, such as potassium soap
Soap
In chemistry, soap is a salt of a fatty acid.IUPAC. "" Compendium of Chemical Terminology, 2nd ed. . Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford . XML on-line corrected version: created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN...

s. Potassium metal has only a few special applications, being replaced in most chemical reactions with sodium metal.

Potassium ion is necessary for the function of all living cells. Potassium ion diffusion is a key mechanism in nerve transmission, and potassium depletion in animals, including humans, results in various cardiac dysfunctions. Potassium is found in especially high concentrations within plant cells, and in a mixed diet, it is mostly concentrated in fruits. The high concentration of potassium in plants, associated with comparatively low amounts of sodium there, historically resulted in potassium first being isolated from potash
Potash
Potash is the common name for various mined and manufactured salts that contain potassium in water-soluble form. In some rare cases, potash can be formed with traces of organic materials such as plant remains, and this was the major historical source for it before the industrial era...

, the ashes of plants, giving the element its name. Heavy crop production rapidly depletes soils of potassium, and agricultural fertilizers consume 95% of global potassium chemical production.

Physical



Potassium atoms have 19 electrons, which is one more than the extremely stable configuration of argon. A potassium atom is thus much more likely to lose the "extra" electron than to gain one; however, the alkalide
Alkalide
An alkalide is a chemical compound in which alkali metals are anions . Such species are notable because alkali metals were previously thought to appear in salts only as cations...

 ions, K, are known. Because of the low first ionization energy (418.8 kJ/mol) the potassium atom easily loses an electron and oxidizes into the monopositive cation, K+. This process requires so little energy that potassium is readily oxidized by atmospheric oxygen. In contrast the second ionization energy, is very high (3052 kJ/mol), because removal of two electrons breaks the stable noble gas electronic configuration. Potassium therefore does not readily form compounds with the oxidation state of +2 (or higher).

Potassium is the second least dense metal after lithium
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...

. It is a soft solid that has a low melting point and can easily be cut with a knife. Freshly cut potassium is silvery in appearance, but it begins to tarnish toward gray immediately after being exposed to air. In a flame test
Flame test
A flame test is a procedure used in chemistry to detect the presence of certain metal ions, based on each element's characteristic emission spectrum. The color of flames in general also depends on temperature; see flame color....

, potassium and its compounds emit a lilac color with a peak emission wavelength of 766.5 nm (see movie below).

Chemical


Potassium is an extremely active metal, which reacts violently with oxygen and water in air. With oxygen, it converts to potassium peroxide
Potassium peroxide
Potassium peroxide is an inorganic compound with the molecular formula K2O2. It is formed as potassium reacts with oxygen in the air, along with potassium oxide and potassium superoxide ....

 and with water potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...

. The reaction of potassium with water is dangerous because of its violent and sufficient exothermic character and release of hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 gas. Hydrogen reacts again with atmospheric oxygen, producing water which reacts with the remaining potassium. This reaction requires only traces of water; because of this, potassium and its liquid alloy — NaK
NaK
NaK, or sodium-potassium alloy, an alloy, of potassium , and sodium , is usually liquid at room temperature. Various commercial grades are available. NaK is highly reactive with water and may catch fire when exposed to air, so must be handled with special precautions...

 — are potent desiccant
Desiccant
A desiccant is a hygroscopic substance that induces or sustains a state of dryness in its local vicinity in a moderately well-sealed container....

s which can be used to dry solvent
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...

s prior to distillation.

Because of the sensitivity of potassium to water and air, the reactions are only possible in inert atmosphere, such as argon
Argon
Argon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...

 gas using air-free technique
Air-free technique
Air-free techniques refer to a range of manipulations in the chemistry laboratory for the handling of compounds that are air-sensitive. These techniques prevent the compounds from reacting with components of air, usually water and oxygen; less commonly carbon dioxide and nitrogen...

s. Potassium does not react with most hydrocarbons, such as mineral oil or kerosene
Kerosene
Kerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin or paraffin oil in the United Kingdom, Hong Kong, Ireland and South Africa, is a combustible hydrocarbon liquid. The name is derived from Greek keros...

. It readily dissolves in liquid ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

, 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. In a pure solution, potassium slowly reacts with ammonia to form KNH2, but this reaction is accelerated by minute amounts of transition metal salts. It can reduce the salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...

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. For example, the preparation of Rieke magnesium employs potassium as the reductant:
MgCl2
Magnesium chloride
Magnesium chloride is the name for the chemical compounds with the formulas MgCl2 and its various hydrates MgCl2x. These salts are typical ionic halides, being highly soluble in water. The hydrated magnesium chloride can be extracted from brine or sea water...

  + 2 K → Mg + 2 KCl

Compounds


The only common oxidation state for potassium is +1. Potassium metal is a powerful reducing agent which is easily oxidized to the monopositive cation, K+. Once oxidized, it is very stable and difficult to reduce back to the metal.

Potassium hydroxide reacts readily with carbon dioxide to produce potassium carbonate
Potassium carbonate
Potassium carbonate is a white salt, soluble in water , which forms a strongly alkaline solution. It can be made as the product of potassium hydroxide's absorbent reaction with carbon dioxide. It is deliquescent, often appearing a damp or wet solid...

, and is used to remove traces of the gas from air. Potassium compounds generally have excellent water solubility, owing to the high hydration energy of the K+ ion. The potassium ion is colorless in water and is very difficult to precipitate
Precipitation (chemistry)
Precipitation is the formation of a solid in a solution or inside anothersolid during a chemical reaction or by diffusion in a solid. When the reaction occurs in a liquid, the solid formed is called the precipitate, or when compacted by a centrifuge, a pellet. The liquid remaining above the solid...

; possible precipitation methods include reactions with sodium tetraphenylborate
Sodium tetraphenylborate
Sodium tetraphenylborate is the organic compound with the formula NaB4. It is a salt, wherein the anion consists of four phenyl rings bonded to boron. This colourless crystalline solid is used to prepare other tetraphenylborate salts, which are often highly soluble in organic solvents...

, hexachloroplatinic acid, and sodium cobaltinitrite
Sodium cobaltinitrite
Sodium cobaltinitrite is a coordination compound with the formula Na3Co6. The anion of this yellow-coloured salt consists of a cobalt center bound to six nitrito ligands. It is used as a qualitative test for potassium and ammonium ions . Although the sodium salt is soluble in water, those of...

.

Potassium oxidizes faster than most metals and forms oxide
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....

s with oxygen-oxygen bonds; as do all alkali metals except lithium. Three species are formed during the reaction: potassium oxide
Potassium oxide
Potassium oxide is an ionic compound of potassium and oxygen. This pale yellow solid, the simplest oxide of potassium, is a rarely encountered, highly reactive compound...

, potassium peroxide
Potassium peroxide
Potassium peroxide is an inorganic compound with the molecular formula K2O2. It is formed as potassium reacts with oxygen in the air, along with potassium oxide and potassium superoxide ....

, and potassium superoxide
Potassium superoxide
Potassium superoxide is the chemical compound with the formula KO2. This rare salt of the superoxide ion is produced by burning molten potassium in pure oxygen...

, which contain three different oxygen-based ions: oxide , peroxide
Peroxide
A peroxide is a compound containing an oxygen–oxygen single bond or the peroxide anion .The O−O group is called the peroxide group or peroxo group. In contrast to oxide ions, the oxygen atoms in the peroxide ion have an oxidation state of −1.The simplest stable peroxide is hydrogen peroxide...

 , and superoxide
Superoxide
A superoxide, also known by the obsolete name hyperoxide, is a compound that possesses the superoxide anion with the chemical formula O2−. The systematic name of the anion is dioxide. It is important as the product of the one-electron reduction of dioxygen O2, which occurs widely in nature...

 . The last two species, especially the superoxide
Superoxide
A superoxide, also known by the obsolete name hyperoxide, is a compound that possesses the superoxide anion with the chemical formula O2−. The systematic name of the anion is dioxide. It is important as the product of the one-electron reduction of dioxygen O2, which occurs widely in nature...

, are rare and are formed only in reaction with very electropositive
Electronegativity
Electronegativity, symbol χ , is a chemical property that describes the tendency of an atom or a functional group to attract electrons towards itself. An atom's electronegativity is affected by both its atomic number and the distance that its valence electrons reside from the charged nucleus...

 metals; these species contain oxygen—oxygen bonds. All potassium—oxygen binary compounds are known to react with water violently, forming potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...

. This compound is a very strong alkali, and 1.21 kg
Kilogram
The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...

 of it can dissolve as much as a liter of water.

In aqueous solution


Potassium compounds are typically highly ionic and thus most of them are soluble in water. The main species in water are the aquo complexes [K(H2O)n]+ where n = 6 and 7. Some of the few salts that are poorly soluble include potassium tetraphenylborate
Potassium tetraphenylborate
Potassium tetraphenylborate is a water-insoluble salt of potassium . It is, however, soluble in organic solvents....

, potassium hexachloroplatinate
Potassium hexachloroplatinate
Potassium hexachloroplatinate, an inorganic compound, is an example of a comparatively insoluble potassium salt.The precipitation of this compound from solutions of hexachloroplatinic acid was formerly used for the determination of potassium by gravimetry....

, and potassium cobaltinitrite
Potassium cobaltinitrite
Potassium cobaltinitrite, IUPAC name potassium hexanitritocobaltate, is a coordination compound with the formula K3[Co6]. The anion of this yellow-coloured salt consists of a cobalt center bound to six nitrito ligands. It is insoluble in water and is precipitated as yellow solids.It was first made...

.

Isotopes



There are 24 known isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...

s of potassium, three of which occur naturally: 39K (93.3%), 40K (0.0117%), and 41K (6.7%). Naturally occurring 40K has a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...

 of 1.250×109 years. It decays to stable 40Ar
Argon
Argon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...

 by electron capture
Electron capture
Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino...

 or positron emission
Positron emission
Positron emission or beta plus decay is a type of beta decay in which a proton is converted, via the weak force, to a neutron, releasing a positron and a neutrino....

 (11.2%) or to stable 40Ca
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

 by beta decay
Beta decay
In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...

 (88.8%).
The decay of 40K to 40Ar enables a commonly used method for dating rocks. The conventional K-Ar dating method
Potassium-argon dating
Potassium–argon dating or K–Ar dating is a radiometric dating method used in geochronology and archeology. It is based on measurement of the product of the radioactive decay of an isotope of potassium into argon . Potassium is a common element found in many materials, such as micas, clay minerals,...

 depends on the assumption that the rocks contained no argon at the time of formation and that all the subsequent radiogenic argon (i.e., 40Ar) was quantitatively retained. Mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

s are dated by measurement of the concentration of potassium and the amount of radiogenic 40Ar that has accumulated. The minerals that are best suited for dating include biotite
Biotite
Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula . More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers...

, muscovite
Muscovite
Muscovite is a phyllosilicate mineral of aluminium and potassium with formula KAl22, or 236. It has a highly-perfect basal cleavage yielding remarkably-thin laminæ which are often highly elastic...

, metamorphic hornblende
Hornblende
Hornblende is a complex inosilicate series of minerals .It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole....

, and volcanic feldspar
Feldspar
Feldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust....

; whole rock samples from volcanic flows and shallow instrusives
Igneous rock
Igneous rock is one of the three main rock types, the others being sedimentary and metamorphic rock. Igneous rock is formed through the cooling and solidification of magma or lava...

 can also be dated if they are unaltered. Outside of dating, potassium isotopes have been used as tracer
Radioactive tracer
A radioactive tracer, also called a radioactive label, is a substance containing a radioisotope that is used to measure the speed of chemical processes and to track the movement of a substance through a natural system such as a cell or tissue...

s in studies of weathering
Weathering
Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...

 and for nutrient cycling studies because potassium is a macronutrient required for life
Life
Life is a characteristic that distinguishes objects that have signaling and self-sustaining processes from those that do not, either because such functions have ceased , or else because they lack such functions and are classified as inanimate...

.

40K 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. In healthy animals and people, 40K represents the largest source of radioactivity, greater even than 14C
Carbon-14
Carbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon with a nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues , to date archaeological, geological, and hydrogeological...

. In a human body of 70 kg mass, about 4,400 nuclei of 40K decay per second. The activity of natural potassium is 31 Bq
Becquerel
The becquerel is the SI-derived unit of radioactivity. One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The Bq unit is therefore equivalent to an inverse second, s−1...

/g.

Creation and occurrence




Potassium is formed in the universe
Universe
The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...

 by nucleosynthesis
Nucleosynthesis
Nucleosynthesis is the process of creating new atomic nuclei from pre-existing nucleons . It is thought that the primordial nucleons themselves were formed from the quark–gluon plasma from the Big Bang as it cooled below two trillion degrees...

 from lighter atoms. The stable form of potassium is created in supernova
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...

s via the explosive Oxygen-burning process.

Elemental potassium does not occur in nature because it reacts violently with water (see section Precautions below). As various compounds, potassium makes up about 2.6% of the weight of the Earth's crust and is the seventh most abundant element, similar in abundance to sodium at approximately 1.8% of the crust. In seawater, potassium at 0.39 g/L (0.039 wt/v%) is far less abundant than sodium at 10.8 g/L (1.08 wt/v%).

Orthoclase
Orthoclase
Orthoclase is an important tectosilicate mineral which forms igneous rock. The name is from the Greek for "straight fracture," because its two cleavage planes are at right angles to each other. Alternate names are alkali feldspar and potassium feldspar...

 (potassium feldspar) is a common rock-forming mineral. Granite
Granite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...

 for example contains 5% potassium which is well above the average in the Earth's crust. Sylvite
Sylvite
Sylvite is potassium chloride in natural mineral form. It forms crystals in the isometric system very similar to normal rock salt, halite . The two are, in fact, isomorphous. Sylvite is colorless to white with shades of yellow and red due to inclusions. It has a Mohs hardness of 2.5 and a specific...

 (KCl), carnallite
Carnallite
Carnallite is an evaporite mineral, a hydrated potassium magnesium chloride with formula: KMgCl3·6. It is variably colored yellow to white, reddish, and sometimes colorless or blue. It is usually massive to fibrous with rare pseudohexagonal orthorhombic crystals...

 (KCl·MgCl2·6(H2O)), kainite
Kainite
Kainite is a mineral salt that consists of potassium chloride and magnesium sulfate and is used as a fertilizer. This mineral is dull and soft, is colored white through yellow to red and is found in the Stassfurt salt mines in Saxony, Germany...

 (MgSO4·KCl·3H2O) and langbeinite
Langbeinite
Langbeinite is a potassium magnesium sulfate mineral with formula: K2Mg23. Langbeinite crystallizes in the isometric - tetartoidal system as transparent colorless or white with pale tints of yellow to green and violet crystalline masses. It has a vitreous luster. The Mohs hardness is 3.5 to 4 and...

 (MgSO4·K2SO4)) are the minerals found in large evaporite
Evaporite
Evaporite is a name for a water-soluble mineral sediment that result from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporate deposits, marine which can also be described as ocean deposits, and non-marine which are found in standing bodies of...

 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
Potassium nitrate
Potassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...

) 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.

History


Neither elemental potassium nor potassium salts (as separate entities from other salts) were known in Roman
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....

 times, and the Latin name of the element is not Classical Latin
Classical Latin
Classical Latin in simplest terms is the socio-linguistic register of the Latin language regarded by the enfranchised and empowered populations of the late Roman republic and the Roman empire as good Latin. Most writers during this time made use of it...

 but rather neo-Latin
New Latin
The term New Latin, or Neo-Latin, is used to describe the Latin language used in original works created between c. 1500 and c. 1900. Among other uses, Latin during this period was employed in scholarly and scientific publications...

. The Latin name kalium was taken from the word "alkali
Alkali
In chemistry, an alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Some authors also define an alkali as a base that dissolves in water. A solution of a soluble base has a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base,...

", which in turn came from al-qalyah "plant ashes." The similar-sounding English term alkali
Alkali
In chemistry, an alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Some authors also define an alkali as a base that dissolves in water. A solution of a soluble base has a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base,...

 is from this same root (potassium in Modern Standard Arabic is بوتاسيوم ‹bootasyoom›).
The English name for the element potassium comes from the word "potash
Potash
Potash is the common name for various mined and manufactured salts that contain potassium in water-soluble form. In some rare cases, potash can be formed with traces of organic materials such as plant remains, and this was the major historical source for it before the industrial era...

", referring to the method by which potash was obtained – leaching the ash of burnt wood or tree leaves and evaporating the solution in a pot. 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, it was not understood for most of its history to be a fundamentally different substance from sodium mineral salts. Georg Ernst Stahl
Georg Ernst Stahl
Georg Ernst Stahl was a German chemist and physician.He was born at Ansbach. Having graduated in medicine at the University of Jena in 1683, he became court physician to Duke Johann Ernst of Sachsen Weimar in 1687...

 obtained experimental evidence which led him to suggest the fundamental difference of sodium and potassium salts in 1702, and Henri Louis Duhamel du Monceau 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 Lavoisier
Antoine-Laurent de Lavoisier , the "father of modern chemistry", was a French nobleman prominent in the histories of chemistry and biology...

 did include the alkali in his list of chemical elements in 1789.

Potassium metal was first isolated in 1807 in England by Sir Humphry Davy
Humphry Davy
Sir Humphry Davy, 1st Baronet FRS MRIA was a British chemist and inventor. He is probably best remembered today for his discoveries of several alkali and alkaline earth metals, as well as contributions to the discoveries of the elemental nature of chlorine and iodine...

, who derived it from caustic potash
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...

 (KOH), by the use of electrolysis of the molten salt with the newly discovered voltaic pile
Voltaic pile
A voltaic pile is a set of individual Galvanic cells placed in series. The voltaic pile, invented by Alessandro Volta in 1800, was the first electric battery...

. Potassium was the first metal that was isolated by electrolysis. Later in the same year, Davy reported extraction of the metal sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 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.

For a long time the only significant applications for potash were the production of glass, bleach, and soap. Potassium soaps from animal fats and vegetable oils were especially prized, as they tended to be more water-soluble and of softer texture, and were known as soft soap
Soap
In chemistry, soap is a salt of a fatty acid.IUPAC. "" Compendium of Chemical Terminology, 2nd ed. . Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford . XML on-line corrected version: created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN...

s. The discovery by Justus Liebig 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
The chemical compound potassium chloride is a metal halide salt composed of potassium and chlorine. In its pure state, it is odorless and has a white or colorless vitreous crystal appearance, with a crystal structure that cleaves easily in three directions. Potassium chloride crystals are...

 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, approximately northeast of Aschersleben, and south of Magdeburg. Pop. 23,538....

, 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.

Commercial production



Potassium salts such as carnallite
Carnallite
Carnallite is an evaporite mineral, a hydrated potassium magnesium chloride with formula: KMgCl3·6. It is variably colored yellow to white, reddish, and sometimes colorless or blue. It is usually massive to fibrous with rare pseudohexagonal orthorhombic crystals...

, langbeinite
Langbeinite
Langbeinite is a potassium magnesium sulfate mineral with formula: K2Mg23. Langbeinite crystallizes in the isometric - tetartoidal system as transparent colorless or white with pale tints of yellow to green and violet crystalline masses. It has a vitreous luster. The Mohs hardness is 3.5 to 4 and...

, polyhalite
Polyhalite
Polyhalite is an evaporite mineral, a hydrated sulfate of potassium, calcium and magnesium with formula: K2Ca2Mg4·2. Polyhalite crystallizes in the triclinic system although crystals are very rare. The normal habit is massive to fibrous. It is typically colorless, white to gray, although it...

, and sylvite
Sylvite
Sylvite is potassium chloride in natural mineral form. It forms crystals in the isometric system very similar to normal rock salt, halite . The two are, in fact, isomorphous. Sylvite is colorless to white with shades of yellow and red due to inclusions. It has a Mohs hardness of 2.5 and a specific...

 form extensive deposits in ancient lake and seabed
Seabed
The seabed is the bottom of the ocean.- Ocean structure :Most of the oceans have a common structure, created by common physical phenomena, mainly from tectonic movement, and sediment from various sources...

s, making extraction of potassium salts in these environments commercially viable. The principal source of potassium – potash
Potash
Potash is the common name for various mined and manufactured salts that contain potassium in water-soluble form. In some rare cases, potash can be formed with traces of organic materials such as plant remains, and this was the major historical source for it before the industrial era...

 – is mined in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

, Belarus
Belarus
Belarus , officially the Republic of Belarus, is a landlocked country in Eastern Europe, bordered clockwise by Russia to the northeast, Ukraine to the south, Poland to the west, and Lithuania and Latvia to the northwest. Its capital is Minsk; other major cities include Brest, Grodno , Gomel ,...

, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

, Israel
Israel
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...

, United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, Jordan
Jordan
Jordan , officially the Hashemite Kingdom of Jordan , Al-Mamlaka al-Urduniyya al-Hashemiyya) is a kingdom on the East Bank of the River Jordan. The country borders Saudi Arabia to the east and south-east, Iraq to the north-east, Syria to the north and the West Bank and Israel to the west, sharing...

, and other places around the world. The first mined deposits were located near Staßfurt, Germany, but the deposits span from Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

 over Germany into Poland. They are located in the Zechstein
Zechstein
The Zechstein is a unit of sedimentary rock layers of Middle to Late Permian age located in the European Permian Basin which stretches from the east coast of England to northern Poland...

 and were deposited in the Middle to Late Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...

. The largest deposits ever found lie 1000 meters (3000 feet) below the surface of the Canadian province of Saskatchewan
Saskatchewan
Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....

. The deposits are located in the Elk Point Group
Elk Point Group
The Elk Point Group is a stratigraphical unit of Middle Devonian age in the Western Canadian Sedimentary Basin.It takes the name from the town of Elk Point, and was first described in the Anglo-Canadian Elk Point No...

 produced in the Middle Devonian. Saskatchewan, where several large mines have operated since the 1960s, pioneered the use of freezing of wet sands (the Blairmore formation) in order to drive mine shafts through them. The main potash mining company in Saskatchewan is the Potash Corporation of Saskatchewan
Potash Corporation of Saskatchewan
The Potash Corporation of Saskatchewan Inc. , also referred to as PotashCorp, is a Canadian corporation based in Saskatoon, Saskatchewan. The company is the world's largest potash producer and the third largest producers of nitrogen and phosphate, three primary crop nutrients used to produce...

. The water of the Dead Sea
Dead Sea
The Dead Sea , also called the Salt Sea, is a salt lake bordering Jordan to the east and Israel and the West Bank to the west. Its surface and shores are below sea level, the lowest elevation on the Earth's surface. The Dead Sea is deep, the deepest hypersaline lake in the world...

 is used by Israel and Jordan as a source for potash, while the concentration in normal oceans is too low for commercial production.
Several methods are applied to separate the potassium salts from the present sodium and magnesium compounds. The mostly used method is to precipitate some compounds relying on the solubility difference of the salts at different temperatures. 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 heap
Slag heap
A spoil tip is a pile built of accumulated spoil - the overburden removed during coal and ore mining. These waste materials are generally composed of shale, as well as smaller quantities of carboniferous sandstone and various other residues...

s. Most of the mined potassium minerals end up as 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
Electrolysis
In chemistry and manufacturing, electrolysis is a method of using a direct electric current to drive an otherwise non-spontaneous chemical reaction...

 of its hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...

 in a process that has changed little since Davy
Humphry Davy
Sir Humphry Davy, 1st Baronet FRS MRIA was a British chemist and inventor. He is probably best remembered today for his discoveries of several alkali and alkaline earth metals, as well as contributions to the discoveries of the elemental nature of chlorine and iodine...

. 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
The chemical compound potassium chloride is a metal halide salt composed of potassium and chlorine. In its pure state, it is odorless and has a white or colorless vitreous crystal appearance, with a crystal structure that cleaves easily in three directions. Potassium chloride crystals are...

 in a chemical equilibrium reaction became the dominant method in the 1950s. The production of sodium potassium alloy
NaK
NaK, or sodium-potassium alloy, an alloy, of potassium , and sodium , is usually liquid at room temperature. Various commercial grades are available. NaK is highly reactive with water and may catch fire when exposed to air, so must be handled with special precautions...

s is possible by changing the reaction time and the amount of sodium used in the reaction. The Griesheimer process employing the reaction of potassium fluoride
Potassium fluoride
Potassium fluoride is the chemical compound with the formula KF. After hydrogen fluoride, KF is the primary source of the fluoride ion for applications in manufacturing and in chemistry. It is an alkali metal halide and occurs naturally as the rare mineral carobbiite...

 with calcium carbide
Calcium carbide
thumb|right|Calcium carbide.Calcium carbide is a chemical compound with the chemical formula of CaC2. The pure material is colorless, however pieces of technical grade calcium carbide are grey or brown and consist of only 80-85% of CaC2 . Because of presence of PH3, NH3, and H2S it has a...

 was also used to produce potassium.
Na + KCl → NaCl + K                      (Thermal method)
2 KF + CaC2 → 2K + CaF2 + 2 C       (Griesheimer process)


Reagent-grade
Reagent
A reagent is a "substance or compound that is added to a system in order to bring about a chemical reaction, or added to see if a reaction occurs." Although the terms reactant and reagent are often used interchangeably, a reactant is less specifically a "substance that is consumed in the course of...

 potassium metal cost about $10.00/pound
Pound (mass)
The pound or pound-mass is a unit of mass used in the Imperial, United States customary and other systems of measurement...

 ($22/kg) in 2010 when purchased in tonne
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...

 quantities. Lower purity metal is considerably cheaper. The market is volatile due to the difficulty of the long-term storage of the metal. It must be stored under a dry inert gas
Inert gas
An inert gas is a non-reactive gas used during chemical synthesis, chemical analysis, or preservation of reactive materials. Inert gases are selected for specific settings for which they are functionally inert since the cost of the gas and the cost of purifying the gas are usually a consideration...

 atmosphere or anhydrous
Anhydrous
As a general term, a substance is said to be anhydrous if it contains no water. The way of achieving the anhydrous form differs from one substance to another...

 mineral oil
Mineral oil
A mineral oil is any of various colorless, odorless, light mixtures of alkanes in the C15 to C40 range from a non-vegetable source, particularly a distillate of petroleum....

 to prevent the formation of a surface layer of potassium superoxide
Potassium superoxide
Potassium superoxide is the chemical compound with the formula KO2. This rare salt of the superoxide ion is produced by burning molten potassium in pure oxygen...

. This superoxide is a pressure-sensitive explosive which will detonate when scratched. The resulting explosion will usually start a fire which is difficult to extinguish.

Biochemical function



Potassium is the eighth or ninth most common element by mass (0.2%) in the human body, so that a 60 kg adult contains a total of about 120 grams of potassium. The body
Composition of the human body
The composition of the human body can be looked at from several different points of view.By mass, human cells consist of 65–90% water . Oxygen therefore contributes a majority of a human body's mass...

 has about as much potassium as sulfur and chlorine, and only the major minerals calcium and phosphorus are more abundant.

Potassium cations
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

 are important in neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...

 (brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

 and nerve
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...

) function, and in influencing osmotic balance
Osmoregulation
Osmoregulation is the active regulation of the osmotic pressure of an organism's fluids to maintain the homeostasis of the organism's water content; that is it keeps the organism's fluids from becoming too diluted or too concentrated. Osmotic pressure is a measure of the tendency of water to move...

 between cells and the interstitial fluid
Extracellular fluid
Extracellular fluid usually denotes all body fluid outside of cells. The remainder is called intracellular fluid.In some animals, including mammals, the extracellular fluid can be divided into two major subcompartments, interstitial fluid and blood plasma...

, with their distribution mediated in all animals (but not in all plants) by the so-called Na+/K+-ATPase
Na+/K+-ATPase
Na+/K+-ATPase is an enzyme located in the plasma membrane in all animals.- Sodium-potassium pumps :Active transport is responsible for cells containing relatively high...

 pump. This ion pump uses ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...

 to pump three sodium ions out of the cell and two potassium ions into the cell, thus creating an electrochemical gradient over the cell membrane. In addition, the highly selective potassium ion channels (which are tetramers) are crucial for the hyperpolarization
Hyperpolarization (biology)
Hyperpolarization is a change in a cell's membrane potential that makes it more negative. It is the opposite of a depolarization.Hyperpolarization is often caused by efflux of K+ through K+ channels, or influx of Cl– through Cl– channels. On the other hand, influx of cations, e.g...

, in for example neurons, after an action potential is fired. The most recently resolved potassium ion channel is KirBac3.1, which gives 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.

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.

Membrane polarization


Potassium is also important in preventing muscle contraction
Muscle contraction
Muscle fiber generates tension through the action of actin and myosin cross-bridge cycling. While under tension, the muscle may lengthen, shorten, or remain the same...

 and the sending of all nerve impulses in animals through action potential
Action potential
In physiology, an action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and...

s. By nature of their electrostatic and chemical properties, K+ ions are larger than Na+ ions, and ion channels and pumps in cell membranes can distinguish between the two types of ions, actively pumping or passively allowing one of the two ions to pass, while blocking the other.

A shortage of potassium in body fluids may cause a potentially fatal condition known as hypokalemia
Hypokalemia
Hypokalemia or hypokalaemia , also hypopotassemia or hypopotassaemia , refers to the condition in which the concentration of potassium in the blood is low...

, typically resulting from vomiting
Vomiting
Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...

, diarrhea
Diarrhea
Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...

, and/or increased diuresis
Polyuria
Polyuria is a condition usually defined as excessive or abnormally large production or passage of urine . Frequent urination is sometimes included by definition, but is nonetheless usually an accompanying symptom...

. Deficiency symptoms include muscle weakness, paralytic ileus, ECG abnormalities, decreased reflex response and in severe cases respiratory paralysis, alkalosis
Alkalosis
Alkalosis refers to a condition reducing hydrogen ion concentration of arterial blood plasma . Generally, alkalosis is said to occur when pH of the blood exceeds 7.45. The opposite condition is acidosis .-Causes:...

 and cardiac arrhythmia.

Filtration and excretion


Potassium is an essential mineral micronutrient
Micronutrient
Micronutrients are nutrients required by humans and other living things throughout life in small quantities to orchestrate a whole range of physiological functions, but which the organism itself cannot produce. For people, they include dietary trace minerals in amounts generally less than 100...

 in human nutrition; it is the major cation (positive ion) inside animal cells, and it is thus important in maintaining fluid and electrolyte
Electrolyte
In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....

 balance in the body. Sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 makes up most of the cations of blood plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...

 at a reference range of about 145 milliequivalents per liter (mEq/L; 3.345 grams), and potassium makes up most of the cell fluid
Cytosol
The cytosol or intracellular fluid is the liquid found inside cells, that is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondrion into compartments....

 cations at about 150 mEq/L (4.8 grams). Plasma is filtered through the glomerulus
Glomerulus
A glomerulus is a capillary tuft that is involved in the first step of filtering blood to form urine.A glomerulus is surrounded by Bowman's capsule, the beginning component of nephrons in the vertebrate kidney. A glomerulus receives its blood supply from an afferent arteriole of the renal...

 of the kidneys in enormous amounts, about 180 liters per day. Thus 602 grams of sodium and 33 grams of potassium are filtered each day. All but the 1–10 grams of sodium and the 1–4 grams of potassium likely to be in the diet must be reabsorbed. Sodium must be reabsorbed in such a way as to keep the blood volume exactly right and the osmotic pressure correct; potassium must be reabsorbed in such a way as to keep serum concentration as close as possible to 4.8 mEq/L (about 0.190 g/L). Sodium pumps in the kidneys must always operate to conserve sodium. Potassium must sometimes be conserved also, but as the amount of potassium in the blood plasma is very small and the pool of potassium in the cells is about thirty 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 secreted twice and reabsorbed three times before the urine reaches the collecting tubules. At that point, it 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.

If potassium were removed from the diet, there would remain a minimum obligatory kidney excretion of about 200 mg per day when the serum declines to 3.0–3.5 mEq/L in about one week, and can never be cut off completely, resulting in hypokalemia
Hypokalemia
Hypokalemia or hypokalaemia , also hypopotassemia or hypopotassaemia , refers to the condition in which the concentration of potassium in the blood is low...

 and even death.

The potassium moves passively through pores in the cell membrane. When ions move through pumps there is a gate in the pumps on either side of the cell membrane and only one gate can be open at once. As a result, approximately 100 ions are forced through per second. Pores have only one gate, and there only one kind of ion can stream through, at 10 million to 100 million ions per second. The pores require calcium in order to open although it is thought that the calcium works 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.

Adequate intake


A potassium intake sufficient to support life can generally be guaranteed by eating a variety of foods. Clear cases of potassium deficiency (as defined by symptoms, signs and a below-normal blood level of the element) are rare in healthy individuals. Foods rich in potassium include parsley
Parsley
Parsley is a species of Petroselinum in the family Apiaceae, native to the central Mediterranean region , naturalized elsewhere in Europe, and widely cultivated as an herb, a spice and a vegetable.- Description :Garden parsley is a bright green hairless biennial herbaceous plant in temperate...

, dried apricots, dried milk, chocolate
Chocolate
Chocolate is a raw or processed food produced from the seed of the tropical Theobroma cacao tree. Cacao has been cultivated for at least three millennia in Mexico, Central and South America. Its earliest documented use is around 1100 BC...

, various nuts
Nut (fruit)
A nut is a hard-shelled fruit of some plants having an indehiscent seed. While a wide variety of dried seeds and fruits are called nuts in English, only a certain number of them are considered by biologists to be true nuts...

 (especially almonds and pistachios), potato
Potato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...

es, bamboo shoots
Bamboo Shoots
Bamboo Shoots is an American four-piece musical group based out of Brooklyn, New York and suburban New Jersey. They are known for their dueling, two-person rhythm section and their South Asian identity and influence...

, banana
Banana
Banana is the common name for herbaceous plants of the genus Musa and for the fruit they produce. Bananas come in a variety of sizes and colors when ripe, including yellow, purple, and red....

s, avocado
Avocado
The avocado is a tree native to Central Mexico, classified in the flowering plant family Lauraceae along with cinnamon, camphor and bay laurel...

s, soybeans, and bran
Bran
Bran is the hard outer layer of grain and consists of combined aleurone and pericarp. Along with germ, it is an integral part of whole grains, and is often produced as a by-product of milling in the production of refined grains. When bran is removed from grains, the grains lose a portion of their...

, although it is also present in sufficient quantities in most fruits, vegetables, meat and fish.

Optimal intake


Epidemiological studies and studies in animals subject to hypertension indicate that diets high in potassium can reduce the risk of hypertension
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...

 and possibly stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...

 (by a mechanism independent of blood pressure
Blood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...

), and a potassium deficiency combined with an inadequate thiamine
Thiamine
Thiamine or thiamin or vitamin B1 , named as the "thio-vitamine" is a water-soluble vitamin of the B complex. First named aneurin for the detrimental neurological effects if not present in the diet, it was eventually assigned the generic descriptor name vitamin B1. Its phosphate derivatives are...

 intake has produced heart disease in rats. There is some debate regarding the optimal amount of dietary potassium. For example, the 2004 guidelines of the Institute of Medicine
Institute of Medicine
The Institute of Medicine is a not-for-profit, non-governmental American organization founded in 1970, under the congressional charter of the National Academy of Sciences...

 specify a DRI
Dietary Reference Intake
The Dietary Reference Intake is a system of nutrition recommendations from the Institute of Medicine of the U.S. National Academy of Sciences. The DRI system is used by both the United States and Canada and is intended for the general public and health professionals...

 of 4,000 mg of potassium (100 mEq), though most Americans consume only half that amount per day, which would make them formally deficient as regards this particular recommendation. Similarly, in the European Union
European Union
The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...

, particularly in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 and Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

, insufficient potassium intake is somewhat common. Italian researchers reported in a 2011 meta-analysis
Meta-analysis
In statistics, a meta-analysis combines the results of several studies that address a set of related research hypotheses. In its simplest form, this is normally by identification of a common measure of effect size, for which a weighted average might be the output of a meta-analyses. Here the...

 that a 1.64 g higher daily intake of potassium was associated with a 21% lower risk of stroke.

Medical supplementation and disease


Supplements of potassium in medicine are most widely used in conjunction with loop diuretic
Loop diuretic
Loop diuretics are diuretics that act on the ascending loop of Henle in the kidney. They are primarily used in medicine to treat hypertension and edema often due to congestive heart failure or renal insufficiency...

s and thiazide
Thiazide
Thiazide is a term used to describe a type of molecule and a class of diuretics often used to treat hypertension and edema ....

s, classes of diuretics which rid the body of sodium and water, but have the side effect of also causing potassium loss in urine. A variety of medical and non-medical supplements are available. Potassium salts such as potassium chloride may be dissolved in water, but the salty/bitter taste of high concentrations of potassium ion make palatable high concentration liquid supplements difficult to formulate. Typical medical supplemental doses range from 10 mEq (400 mg, about equal to a cup of milk or 6 USfloz. of orange juice) to 20 mEq (800 mg) per dose. Potassium salts are also available in tablets or capsules, which for therapeutic purposes are formulated to allow potassium to leach slowly out of a matrix, as very high concentrations of potassium ion (which might occur next to a solid tablet of potassium chloride) can kill tissue, and cause injury to the gastric or intestinal mucosa. For this reason, non-prescription supplement potassium pills are limited by law in the US to only 99 mg of potassium.
Individuals suffering from kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

 diseases may suffer adverse health effects from consuming large quantities of dietary potassium. End stage renal failure patients undergoing therapy by renal dialysis must observe strict dietary limits on potassium intake, as the kidneys control potassium excretion, and buildup of blood concentrations of potassium (hyperkalemia
Hyperkalemia
Hyperkalemia refers to the condition in which the concentration of the electrolyte potassium in the blood is elevated...

) may trigger fatal cardiac arrhythmia.

Fertilizer



Potassium ions are an essential component of plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

 nutrition and are found in most soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

 types. They are used as a fertilizer
Fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...

 in agriculture
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

, horticulture
Horticulture
Horticulture is the industry and science of plant cultivation including the process of preparing soil for the planting of seeds, tubers, or cuttings. Horticulturists work and conduct research in the disciplines of plant propagation and cultivation, crop production, plant breeding and genetic...

, and hydroponic culture in the form of chloride
Potassium chloride
The chemical compound potassium chloride is a metal halide salt composed of potassium and chlorine. In its pure state, it is odorless and has a white or colorless vitreous crystal appearance, with a crystal structure that cleaves easily in three directions. Potassium chloride crystals are...

 (KCl), sulfate
Potassium sulfate
Potassium sulfate is a non-flammable white crystalline salt which is soluble in water...

 , or nitrate
Potassium nitrate
Potassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...

 . 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 range from 0.5% to 2% of the harvested weight of crops, conventionally expressed as amount of . Modern high-yield
Crop yield
In agriculture, crop yield is not only a measure of the yield of cereal per unit area of land under cultivation, yield is also the seed generation of the plant itself...

 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 mostly produced by decomposition of the complex minerals kainite
Kainite
Kainite is a mineral salt that consists of potassium chloride and magnesium sulfate and is used as a fertilizer. This mineral is dull and soft, is colored white through yellow to red and is found in the Stassfurt salt mines in Saxony, Germany...

 (MgSO4·KCl·3H2O) and langbeinite
Langbeinite
Langbeinite is a potassium magnesium sulfate mineral with formula: K2Mg23. Langbeinite crystallizes in the isometric - tetartoidal system as transparent colorless or white with pale tints of yellow to green and violet crystalline masses. It has a vitreous luster. The Mohs hardness is 3.5 to 4 and...

 (MgSO4·K2SO4). Only a very few fertilizers contain potassium nitrate. In 2005, about 93% of world potassium production was consumed by the fertilizer industry.

Food


The potassium cation is a nutrient necessary for human life and health. Potassium chloride
Potassium chloride
The chemical compound potassium chloride is a metal halide salt composed of potassium and chlorine. In its pure state, it is odorless and has a white or colorless vitreous crystal appearance, with a crystal structure that cleaves easily in three directions. Potassium chloride crystals are...

 is used as a substitute for table salt by those seeking to reduce sodium intake so as to control hypertension
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...

. The USDA
United States Department of Agriculture
The United States Department of Agriculture is the United States federal executive department responsible for developing and executing U.S. federal government policy on farming, agriculture, and food...

 lists tomato paste
Tomato paste
Tomato paste is a thick paste that is made by cooking tomatoes for several hours to reduce moisture, straining them to remove the seeds and skin, and cooking them again to reduce them to a thick, rich concentrate...

, orange juice
Orange juice
Orange juice is a popular beverage made from oranges. It is made by extraction from the fresh fruit, by desiccation and subsequent reconstitution of dried juice, or by concentration of the juice and the subsequent addition of water to the concentrate...

, beet greens, white beans, potato
Potato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...

es, banana
Banana
Banana is the common name for herbaceous plants of the genus Musa and for the fruit they produce. Bananas come in a variety of sizes and colors when ripe, including yellow, purple, and red....

s and many other good dietary sources of potassium, ranked in descending order according to potassium content.

Potassium sodium tartrate (KNaC4H4O6, Rochelle salt) is the main constituent of baking powder
Baking powder
Baking powder is a dry chemical leavening agent used to increase the volume and lighten the texture of baked goods such as muffins, cakes, scones and American-style biscuits. Baking powder works by releasing carbon dioxide gas into a batter or dough through an acid-base reaction, causing bubbles in...

; it is also used in the silvering
Silvering
Silvering is the chemical process of coating glass with a reflective substance. When glass mirrors first gained widespread usage in Europe during the 16th century, most were made of an amalgam of tin and mercury, but by the 19th century mirrors were commonly made through a process by which silver...

 of mirrors. Potassium bromate
Potassium bromate
Potassium bromate , is a bromate of potassium and takes the form of white crystals or powder.-Uses in baking:Potassium bromate is typically used as a flour improver , strengthening the dough and allowing higher rising. It is an oxidizing agent, and under the right conditions, will be completely...

  is a strong oxidizer (E924), used to improve dough strength and rise height. Potassium bisulfite
Potassium bisulfite
Potassium hydrogen sulfite or potassium bisulfite is a chemical compound with the chemical formula KHSO3. It is used during the production of alcoholic beverages as a sterilising agent. This additive is classified as E number E228 under the current EU approved food additive....

  is used as a food preservative, for example in wine
Wine
Wine is an alcoholic beverage, made of fermented fruit juice, usually from grapes. The natural chemical balance of grapes lets them ferment without the addition of sugars, acids, enzymes, or other nutrients. Grape wine is produced by fermenting crushed grapes using various types of yeast. Yeast...

 and beer
Beer
Beer is the world's most widely consumed andprobably oldest alcoholic beverage; it is the third most popular drink overall, after water and tea. It is produced by the brewing and fermentation of sugars, mainly derived from malted cereal grains, most commonly malted barley and malted wheat...

-making (but not in meats). It is also used to bleach
Bleach
Bleach refers to a number of chemicals that remove color, whiten, or disinfect, often via oxidation. Common chemical bleaches include household chlorine bleach , lye, oxygen bleach , and bleaching powder...

 textiles and straw, and in the tanning of leather
Leather
Leather is a durable and flexible material created via the tanning of putrescible animal rawhide and skin, primarily cattlehide. It can be produced through different manufacturing processes, ranging from cottage industry to heavy industry.-Forms:...

s.

Industrial


Major potassium chemicals are potassium hydroxide, potassium carbonate, potassium sulfate, and potassium chloride. Megatons of these compounds are produced annually.

Potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...

  is a strong base, which is used in industry to neutralize strong and weak acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

s, to control pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 and to manufacture potassium salts. It is also used to saponify
Saponification
Saponification is a process that produces soap, usually from fats and lye. In technical terms, saponification involves base hydrolysis of triglycerides, which are esters of fatty acids, to form the sodium salt of a carboxylate. In addition to soap, such traditional saponification processes...

 fat
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...

s and oils, in industrial cleaners, and in hydrolysis
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...

 reactions, for example of esters.

Potassium nitrate
Potassium nitrate
Potassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...

 (KNO3) or saltpeter is obtained from natural sources such as guano
Guano
Guano is the excrement of seabirds, cave dwelling bats, and seals. Guano manure is an effective fertilizer due to its high levels of phosphorus and nitrogen and also its lack of odor. It was an important source of nitrates for gunpowder...

 and evaporites or manufactured via the Haber process
Haber process
The Haber process, also called the Haber–Bosch process, is the nitrogen fixation reaction of nitrogen gas and hydrogen gas, over an enriched iron or ruthenium catalyst, which is used to industrially produce ammonia....

; it is the oxidant in gunpowder
Gunpowder
Gunpowder, also known since in the late 19th century as black powder, was the first chemical explosive and the only one known until the mid 1800s. It is a mixture of sulfur, charcoal, and potassium nitrate - with the sulfur and charcoal acting as fuels, while the saltpeter works as an oxidizer...

 (black powder) and an important agricultural fertilizer. Potassium cyanide
Potassium cyanide
Potassium cyanide is an inorganic compound with the formula KCN. This colorless crystalline compound, similar in appearance to sugar, is highly soluble in water. Most KCN is used in gold mining, organic synthesis, and electroplating. Smaller applications include jewelry for chemical gilding and...

 (KCN) is used industrially to dissolve copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 and precious metals, particularly silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...

 and gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

, by forming complex
Complex (chemistry)
In chemistry, a coordination complex or metal complex, is an atom or ion , bonded to a surrounding array of molecules or anions, that are in turn known as ligands or complexing agents...

es. Its applications include gold mining
Gold mining
Gold mining is the removal of gold from the ground. There are several techniques and processes by which gold may be extracted from the earth.-History:...

, electroplating
Electroplating
Electroplating is a plating process in which metal ions in a solution are moved by an electric field to coat an electrode. The process uses electrical current to reduce cations of a desired material from a solution and coat a conductive object with a thin layer of the material, such as a metal...

, and electroforming
Electroforming
Electroforming is a metal forming process that forms thin parts through the electroplating process. The part is produced by plating a metal skin onto a base form, known as a mandrel, which is removed after plating...

 of these metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

s; it is also used in organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...

 to make nitriles. Potassium carbonate
Potassium carbonate
Potassium carbonate is a white salt, soluble in water , which forms a strongly alkaline solution. It can be made as the product of potassium hydroxide's absorbent reaction with carbon dioxide. It is deliquescent, often appearing a damp or wet solid...

 ( or potash) is used in the manufacture of glass, soap, color TV tubes, fluorescent lamps, textile dyes and pigments. Potassium permanganate (KMnO4) is an oxidizing, bleaching and purification substance and is used for production of saccharin
Saccharin
Saccharin is an artificial sweetener. The basic substance, benzoic sulfilimine, has effectively no food energy and is much sweeter than sucrose, but has a bitter or metallic aftertaste, especially at high concentrations...

. Potassium chlorite (KClO3) is added to matches and explosives. Potassium bromide (KBr) was formerly used as a sedative and in photography.

Potassium chromate
Potassium chromate
Potassium chromate is a yellow chemical indicator used for identifying concentrations of chloride ions in a salt solution with silver nitrate...

 (K2CrO4) is used in ink
Ink
Ink is a liquid or paste that contains pigments and/or dyes and is used to color a surface to produce an image, text, or design. Ink is used for drawing and/or writing with a pen, brush, or quill...

s, dye
Dye
A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....

s, stain
Stain
A stain is a discoloration that can be clearly distinguished from the surface, material, or medium it is found upon. Stains are caused by the chemical or physical interaction of two dissimilar materials...

s (bright yellowish-red color); in explosives and fireworks
Fireworks
Fireworks are a class of explosive pyrotechnic devices used for aesthetic and entertainment purposes. The most common use of a firework is as part of a fireworks display. A fireworks event is a display of the effects produced by firework devices...

; in the tanning of leather, in fly paper and safety matches, but all these uses are due to the properties of chromate
Chromate
Chromate salts contain the chromate anion, CrO42−. Dichromate salts contain the dichromate anion, Cr2O72−. They are oxyanions of chromium in the oxidation state +6. They are moderately strong oxidizing agents.- Chemical properties :...

 ion containment rather than potassium ions.

Niche uses


Potassium compounds are so pervasive that thousands of small uses are in place. The superoxide
Superoxide
A superoxide, also known by the obsolete name hyperoxide, is a compound that possesses the superoxide anion with the chemical formula O2−. The systematic name of the anion is dioxide. It is important as the product of the one-electron reduction of dioxygen O2, which occurs widely in nature...

 KO2 is an orange solid that acts as a portable source of oxygen and a carbon dioxide absorber. It is widely used in respiration systems in mines, submarines and spacecraft as it takes less volume than the gaseous oxygen.
4 KO2 + 2 CO2 → 2 K2CO3 + 3 O2


Potassium cobaltinitrite
Potassium cobaltinitrite
Potassium cobaltinitrite, IUPAC name potassium hexanitritocobaltate, is a coordination compound with the formula K3[Co6]. The anion of this yellow-coloured salt consists of a cobalt center bound to six nitrito ligands. It is insoluble in water and is precipitated as yellow solids.It was first made...

  is used as artist's pigment under the name of Aureolin
Aureolin
Aureolin is a pigment used in oil and watercolor painting. Its color index name is PY40 . It was first made in 1848 by N. W. Fischer in Breslau and its chemical composition is potassium cobaltinitrite.Aureolin is rated as permanent in oils but darkens and fades easily in watercolors...

 or Cobalt
Cobalt
Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....

 yellow.

Laboratory uses


An alloy
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...

 of sodium and potassium, NaK
NaK
NaK, or sodium-potassium alloy, an alloy, of potassium , and sodium , is usually liquid at room temperature. Various commercial grades are available. NaK is highly reactive with water and may catch fire when exposed to air, so must be handled with special precautions...

 is a liquid used as a heat-transfer medium and a desiccant
Desiccant
A desiccant is a hygroscopic substance that induces or sustains a state of dryness in its local vicinity in a moderately well-sealed container....

 for producing dry and air-free solvents
Air-free technique
Air-free techniques refer to a range of manipulations in the chemistry laboratory for the handling of compounds that are air-sensitive. These techniques prevent the compounds from reacting with components of air, usually water and oxygen; less commonly carbon dioxide and nitrogen...

. It can also be used in reactive distillation
Reactive distillation
Reactive distillation is a process where the chemical reactor is also the still. Separation of the product from the reaction mixture does not need a separate distillation step, which saves energy and materials....

. 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 magnetometer
Magnetometer
A magnetometer is a measuring instrument used to measure the strength or direction of a magnetic field either produced in the laboratory or existing in nature...

s.

Precautions


Potassium reacts very violently with water producing potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...

 (KOH) and hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 gas.
2 K (s) + 2 H2O (l) → 2 KOH (aq) + H2↑ (g)


This reaction is exothermic and releases enough heat to ignite the resulting hydrogen. It in turn may explode in the presence of oxygen. Potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...

 is a strong alkali
Alkali
In chemistry, an alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Some authors also define an alkali as a base that dissolves in water. A solution of a soluble base has a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base,...

 which causes skin burns. Finely divided potassium will ignite in air at room temperature. The bulk metal will ignite in air if heated. Because its density is 0.89 g/cm3, burning potassium floats in water that exposes it to atmospheric oxygen. Many common fire extinguishing agents, including water, are either ineffective or make a potassium fire worse. Nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

, argon
Argon
Argon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...

, Sodium chloride
Sodium chloride
Sodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...

 (table salt), sodium carbonate
Sodium carbonate
Sodium carbonate , Na2CO3 is a sodium salt of carbonic acid. It most commonly occurs as a crystalline heptahydrate, which readily effloresces to form a white powder, the monohydrate. Sodium carbonate is domestically well-known for its everyday use as a water softener. It can be extracted from the...

 (soda ash), and silicon dioxide
Silicon dioxide
The chemical compound silicon dioxide, also known as silica , is an oxide of silicon with the chemical formula '. It has been known for its hardness since antiquity...

 (sand) are effective if they are dry. Some Class D
Fire extinguisher
A fire extinguisher or extinguisher, flame entinguisher is an active fire protection device used to extinguish or control small fires, often in emergency situations...

 dry powder extinguishers designed for metal fires are also effective. These agents deprive the fire of oxygen and cool the potassium metal.

Potassium reacts violently with halogens and will detonate in the presence of bromine
Bromine
Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...

. It also reacts explosively with sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...

. During combustion potassium forms peroxides and superoxides. These peroxides may react violently with organic compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

s such as oils. Both peroxides and superoxides may react explosively with metallic potassium.

Because potassium reacts with water vapor present 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 6 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.

Because of the highly reactive nature of potassium metal, it must be handled with great care, with full skin and eye protection and preferably an explosion-resistant barrier between the user and the metal. Ingestion of large amounts of potassium compounds can lead to hyperkalemia
Hyperkalemia
Hyperkalemia refers to the condition in which the concentration of the electrolyte potassium in the blood is elevated...

 strongly influencing the cardiovascular system. Potassium chloride is used in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 for death penalty via lethal injection
Lethal injection
Lethal injection is the practice of injecting a person with a fatal dose of drugs for the express purpose of causing the immediate death of the subject. The main application for this procedure is capital punishment, but the term may also be applied in a broad sense to euthanasia and suicide...

.

See also