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=                             Potassium                              =
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                            Introduction
======================================================================
Potassium is a chemical element; it has symbol K (from Neo-Latin ) and
atomic number19. It is a silvery white metal that is soft enough to
easily cut with a knife. Potassium metal reacts rapidly with
atmospheric oxygen to form flaky white potassium peroxide in only
seconds of exposure. It was first isolated from potash, the ashes of
plants, from which its name derives. In the periodic table, potassium
is one of the alkali metals, all of which have a single valence
electron in the outer electron shell, which is easily removed to
create an ion with a positive charge (which combines with anions to
form salts). In nature, potassium occurs only in ionic salts.
Elemental potassium reacts vigorously with water, generating
sufficient heat to ignite hydrogen emitted in the reaction, and
burning with a lilac-colored flame. It is found dissolved in seawater
(which is 0.04% potassium by weight), and occurs in many minerals such
as orthoclase, a common constituent of granites and other igneous
rocks.

Potassium is chemically very similar to sodium, the previous element
in group 1 of the periodic table. They have a similar first ionization
energy, which allows for each atom to give up its sole outer electron.
It was first suggested in 1702 that they were distinct elements that
combine with the same anions to make similar salts, which was
demonstrated in 1807 when elemental potassium was first isolated via
electrolysis. Naturally occurring potassium is composed of three
isotopes, of which potassium-40 is radioactive. Traces of  are found
in all potassium, and it is the most common radioisotope in the human
body.

Potassium ions are vital for the functioning of all living cells. The
transfer of potassium ions across nerve cell membranes is necessary
for normal nerve transmission; potassium deficiency and excess can
each result in numerous signs and symptoms, including an abnormal
heart rhythm and various electrocardiographic abnormalities. Fresh
fruits and vegetables are good dietary sources of potassium. The body
responds to the influx of dietary potassium, which raises serum
potassium levels, by shifting potassium from outside to inside cells
and increasing potassium excretion by the kidneys.

Most industrial applications of potassium exploit the high solubility
of its compounds in water, such as saltwater soap. Heavy crop
production rapidly depletes the soil of potassium, and this can be
remedied with agricultural fertilizers containing potassium,
accounting for 95% of global potassium chemical production.


                             Etymology
======================================================================
The English name for the element 'potassium' comes from the word
'potash', which refers to an early method of extracting various
potassium salts: placing in a 'pot' the 'ash' of burnt wood or tree
leaves, adding water, heating, and evaporating the solution. When
Humphry Davy first isolated the pure element using electrolysis in
1807, he named it 'potassium', which he derived from the word
'potash'.

The symbol 'K' stems from 'kali', itself from the root word 'alkali',
which in turn comes from  'al-qalyah' 'plant ashes'. In 1797, the
German chemist Martin Klaproth discovered "potash" in the minerals
leucite and lepidolite, and realized that "potash" was not a product
of plant growth but actually contained a new element, which he
proposed calling 'kali'.Klaproth, M. (1797) "Nouvelles données
relatives à l'histoire naturelle de l'alcali végétal" (New data
regarding the natural history of the vegetable alkali), 'Mémoires de
l'Académie royale des sciences et belles-lettres' (Berlin), pp. 9-13 ;
[https://babel.hathitrust.org/cgi/pt?id=mdp.39015073704093;view=1up;seq=103
see p. 13.]  From p. 13: '"Cet alcali ne pouvant donc plus être
envisagé comme un produit de la végétation dans les plantes, occupe
une place propre dans la série des substances primitivement simples du
règne minéral, &I il devient nécessaire de lui assigner un nom,
qui convienne mieux à sa nature.'
'La dénomination de 'Potasche' (potasse) que la nouvelle nomenclature
françoise a consacrée comme nom de tout le genre, ne sauroit faire
fortune auprès des chimistes allemands, qui sentent à quel point la
dérivation étymologique en est vicieuse. Elle est prise en effet de ce
qu'anciennement on se servoit pour la calcination des lessives
concentrées des cendres, de pots de fer ('pott' en dialecte de la
Basse-Saxe) auxquels on a substitué depuis des fours à calciner.'
'Je propose donc ici, de substituer aux mots usités jusqu'ici d'alcali
des plantes, alcali végétal, potasse, &c. celui de 'kali', &
de revenir à l'ancienne dénomination de 'natron', au lieu de dire
alcali minéral, soude &c."'
(This alkali [i.e., potash] -- [which] therefore can no longer be
viewed as a product of growth in plants -- occupies a proper place in
the originally simple series of the mineral realm, and it becomes
necessary to assign it a name that is better suited to its nature.
The name of "potash" ('potasse'), which the new French nomenclature
has bestowed as the name of the entire species [i.e., substance],
would not find acceptance among German chemists, who feel to some
extent [that] the etymological derivation of it is faulty. Indeed, it
is taken from [the vessels] that one formerly used for the roasting of
washing powder concentrated from cinders: iron pots ('pott' in the
dialect of Lower Saxony), for which roasting ovens have been
substituted since then.
Thus I now propose to substitute for the until now common words of
"plant alkali", "vegetable alkali", "potash", etc., that of 'kali' ;
and to return to the old name of 'natron' instead of saying "mineral
alkali", "soda", etc.) In 1807, Humphry Davy produced the element via
electrolysis: in 1809, Ludwig Wilhelm Gilbert proposed the name
'Kalium' for Davy's "potassium". In 1814, the Swedish chemist
Berzelius advocated the name 'kalium' for potassium, with the chemical
symbol 'K'.

The English and French-speaking countries adopted the name
'Potassium', which was favored by Davy and French chemists Joseph
Louis Gay-Lussac and Louis Jacques Thénard, whereas the other Germanic
countries adopted Gilbert and Klaproth's name 'Kalium'. The "Gold
Book" of the International Union of Pure and Applied Chemistry has
designated the official chemical symbol as K.


Physical
==========
Potassium is the second least dense metal after lithium. It is a soft
solid with a low melting point, and can be easily cut with a knife.
Potassium is silvery in appearance, but it begins to tarnish toward
gray immediately on exposure to air. In a flame test, potassium and
its compounds emit a lilac color with a peak emission wavelength of
766.5 nanometers.

Neutral potassium atoms have 19 electrons, one more than the
configuration of the noble gas argon. Because of its low first
ionization energy of 418.8kJ/mol, the potassium atom is much more
likely to lose the last electron and acquire a positive charge,
although negatively charged alkalide  ions are not impossible. In
contrast, the second ionization energy is very high (3052kJ/mol).


Chemical
==========
Potassium reacts with oxygen, water, and carbon dioxide components in
air. With oxygen it forms potassium peroxide. With water potassium
forms potassium hydroxide (KOH). The reaction of potassium with water
can be violently exothermic, especially since the coproduced hydrogen
gas can ignite. Because of this, potassium and the liquid
sodium-potassium (NaK) alloy are potent desiccants, although they are
no longer used as such.


Compounds
===========
Structure of solid potassium superoxide ().

Four oxides of potassium are well studied: potassium oxide (),
potassium peroxide (), potassium superoxide () and potassium ozonide
(). The binary potassium-oxygen compounds react with water forming
KOH.

KOH is a strong base. Illustrating its hydrophilic character, as much
as 1.21 kg of KOH can dissolve in a single liter of water. Anhydrous
KOH is rarely encountered. KOH reacts readily with carbon dioxide ()
to produce potassium carbonate (), and in principle could be used to
remove traces of the gas from air. Like the closely related sodium
hydroxide, KOH reacts with fats to produce soaps.

In general, potassium compounds are ionic and, owing to the high
hydration energy of the  ion, have excellent water solubility. The
main species in water solution are the aquo complexes
{{chem2|[K(H2O)_{'n'}]+}} where 'n' = 6 and 7.

Potassium heptafluorotantalate () is an intermediate in the
purification of tantalum from the otherwise persistent contaminant of
niobium.

Organopotassium compounds illustrate nonionic compounds of potassium.
They feature highly polar covalent K-C bonds. Examples include benzyl
potassium . Potassium intercalates into graphite to give a variety of
graphite intercalation compounds, including .


Isotopes
==========
There are 25 known isotopes of potassium, three of which occur
naturally:  (93.3%),  (0.0117%), and  (6.7%) (by mole fraction).
Naturally occurring potassium-40 has a half-life of  years. It decays
to stable Argon by electron capture or positron emission (11.2%) or to
stable Calcium by beta decay (88.8%). The decay of  to  is the basis
of a common method for dating rocks. The conventional K-Ar dating
method depends on the assumption that the rocks contained no argon at
the time of formation and that all the subsequent radiogenic argon ()
was quantitatively retained. Minerals are dated by measurement of the
concentration of potassium and the amount of radiogenic  that has
accumulated. The minerals best suited for dating include biotite,
muscovite, metamorphic hornblende, and volcanic feldspar; whole rock
samples from volcanic flows and shallow instrusives can also be dated
if they are unaltered. Apart from dating, potassium isotopes have been
used as tracers in studies of weathering and for nutrient cycling
studies because potassium is a macronutrient required for life on
Earth.

occurs in natural potassium (and thus in some commercial salt
substitutes) in sufficient quantity that large bags of those
substitutes can be used as a radioactive source for classroom
demonstrations.  is the radioisotope with the largest abundance in the
human body. In healthy animals and people,  represents the largest
source of radioactivity, greater even than Carbon-14. In a human body
of 70 kg, about 4,400 nuclei of  decay per second. The activity of
natural potassium is 31 Bq/g.


Potash
========
Potash is primarily a mixture of potassium salts because plants have
little or no sodium content, and the rest of a plant's major mineral
content consists of calcium salts of relatively low solubility in
water. While potash has been used since ancient times, its composition
was not understood. Georg Ernst Stahl obtained experimental evidence
that 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
did not include the alkali in his list of chemical elements in 1789.
For a long time the only significant applications for potash were the
production of glass, bleach, soap and gunpowder as potassium nitrate.
Potassium soaps from animal fats and vegetable oils were especially
prized because they tend to be more water-soluble and of softer
texture, and are therefore known as soft soaps. 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 near Staßfurt,
Germany, the production of potassium-containing fertilizers began at
an industrial scale. Other potash deposits were discovered, and by the
1960s Canada became the dominant producer.


Metal
=======
Potassium 'metal' was first isolated in 1807 by Humphry Davy, who
derived it by electrolysis of molten caustic potash (KOH) with the
newly discovered voltaic pile. Potassium was the first metal that was
isolated by electrolysis. Later in the same year, Davy reported
extraction of the metal sodium from a mineral derivative (caustic
soda, NaOH, or lye) rather than a plant salt, by a similar technique,
demonstrating that the elements, and thus the salts, are different.
Although the production of potassium and sodium metal should have
shown that both are elements, it took some time before this view was
universally accepted.

Because of the sensitivity of potassium to water and air, air-free
techniques are normally employed for handling the element. It is
unreactive toward nitrogen and saturated hydrocarbons such as mineral
oil or kerosene. It readily dissolves in liquid ammonia, up to 480 g
per 1000 g of ammonia at 0°C. Depending on the concentration, the
ammonia solutions are blue to yellow, and their electrical
conductivity is similar to that of liquid metals. Potassium slowly
reacts with ammonia to form Potassium amide, but this reaction is
accelerated by minute amounts of transition metal salts. Because it
can reduce the salts to the metal, potassium is often used as the
reductant in the preparation of finely divided metals from their salts
by the Rieke method. Illustrative is the preparation of magnesium:

:


                             Occurrence
======================================================================
Potassium is formed in supernovae by nucleosynthesis from lighter
atoms. Potassium is principally created in Type II supernovae via an
explosive oxygen-burning process. These are nuclear fusion reactions,
not to be confused with chemical burning of potassium in oxygen.  is
also formed in  nucleosynthesis and the neon burning process.

Potassium is the 20th most abundant element in the Solar System and
the 17th most abundant element by weight in the Earth. It makes up
about 2.6% of the weight of the Earth's crust and is the seventh most
abundant element in the crust. The potassium concentration in seawater
is 0.39g/L (0.039 wt/v%), about one twenty-seventh the concentration
of sodium.


Geology
=========
Elemental potassium does not occur in nature because of its high
reactivity. It reacts violently with water and also reacts with
oxygen. Orthoclase (potassium feldspar) is a common rock-forming
mineral. Granite for example contains 5% potassium, which is well
above the average in the Earth's crust. Sylvite (KCl), carnallite (),
kainite () and langbeinite () are the minerals found in large
evaporite deposits worldwide. The deposits often show layers starting
with the least soluble at the bottom and the most soluble on top.
Deposits of niter (potassium nitrate) are formed by decomposition of
organic material in contact with atmosphere, mostly in caves; because
of the good water solubility of niter the formation of larger deposits
requires special environmental conditions.


Mining
========
Potassium salts such as carnallite, langbeinite, polyhalite, and
sylvite form extensive evaporite deposits in ancient lake bottoms and
seabeds, making extraction of potassium salts in these environments
commercially viable. The principal source of potassium - potash - is
mined in Canada, Russia, Belarus, Kazakhstan, Germany, Israel, the
U.S., Jordan, and other places around the world. The first mined
deposits were located near Staßfurt, Germany, but the deposits span
from Great Britain over Germany into Poland. They are located in the
Zechstein and were deposited in the Middle to Late Permian. The
largest deposits ever found lie 1000 m below the surface of the
Canadian province of Saskatchewan. The deposits are located in the Elk
Point Group produced in the Middle Devonian. Saskatchewan, where
several large mines have operated since the 1960s pioneered the
technique of freezing of wet sands (the Blairmore formation) to drive
mine shafts through them. The main potash mining company in
Saskatchewan until its merge was the Potash Corporation of
Saskatchewan, now Nutrien. The water of the Dead Sea is used by Israel
and Jordan as a source of potash, while the concentration in normal
oceans is too low for commercial production at current prices.


Chemical extraction
=====================
Several methods are used to separate potassium salts from sodium and
magnesium compounds. The most-used method is fractional precipitation
using the solubility differences of the salts. Electrostatic
separation of the ground salt mixture is also used in some mines. The
resulting sodium and magnesium waste is either stored underground or
piled up in slag heaps. Most of the mined potassium mineral ends up as
potassium chloride 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 of its hydroxide
in a process that has changed little since it was first used by
Humphry Davy in 1807. Although the electrolysis process was developed
and used in industrial scale in the 1920s, the thermal method by
reacting sodium with potassium chloride in a chemical equilibrium
reaction became the dominant method in the 1950s.
:Na + KCl → NaCl + K
The production of sodium potassium alloys is accomplished by changing
the reaction time and the amount of sodium used in the reaction. The
Griesheimer process employing the reaction of potassium fluoride with
calcium carbide was also used to produce potassium.

:

Reagent-grade potassium metal costs about $10.00/pound ($22/kg) in
2010 when purchased by the tonne. Lower purity metal is considerably
cheaper. The market is volatile because long-term storage of the metal
is difficult. It must be stored in a dry inert gas atmosphere or
anhydrous mineral oil to prevent the formation of a surface layer of
potassium superoxide, a pressure-sensitive explosive that detonates
when scratched. The resulting explosion often starts a fire difficult
to extinguish.


Cation identification
=======================
Potassium is now quantified by ionization techniques, but at one time
it was quantitated by gravimetric analysis.

Reagents used to precipitate potassium salts include sodium
tetraphenylborate, hexachloroplatinic acid, and sodium cobaltinitrite
into respectively potassium tetraphenylborate, potassium
hexachloroplatinate, and potassium cobaltinitrite.
The reaction with sodium cobaltinitrite is illustrative:
:
The potassium cobaltinitrite is obtained as a yellow solid.


Fertilizer
============
Potassium ions are an essential component of plant nutrition and are
found in most soil types. They are used as a fertilizer in
agriculture, horticulture, and hydroponic culture in the form of
chloride (KCl), sulfate (), or nitrate (), representing the 'K' in
'NPK'. Agricultural fertilizers consume 95% of global potassium
chemical production, and about 90% of this potassium is supplied as
KCl. The potassium content of most plants ranges from 0.5% to 2% of
the harvested weight of crops, conventionally expressed as amount of .
Modern high-yield agriculture depends upon fertilizers to replace the
potassium lost at harvest. Most agricultural fertilizers contain
potassium chloride, while potassium sulfate is used for
chloride-sensitive crops or crops needing higher sulfur content. The
sulfate is produced mostly by decomposition of the complex minerals
kainite () and langbeinite (). Only a very few fertilizers contain
potassium nitrate. In 2005, about 93% of world potassium production
was consumed by the fertilizer industry. Furthermore, potassium can
play a key role in nutrient cycling by controlling litter composition.


Potassium citrate
===================
Potassium citrate is used to treat a kidney stone condition called
renal tubular acidosis.


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


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


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

KOH is a strong base, which is used in industry to neutralize strong
and weak acids, to control pH and to manufacture potassium salts. It
is also used to saponify fats and oils, in industrial cleaners, and in
hydrolysis reactions, for example of esters.

Potassium nitrate () or saltpeter is obtained from natural sources
such as guano and evaporites or manufactured via the Haber process; it
is the oxidant in gunpowder (black powder) and an important
agricultural fertilizer. Potassium cyanide (KCN) is used industrially
to dissolve copper and precious metals, in particular silver and gold,
by forming complexes. Its applications include gold mining,
electroplating, and electroforming of these metals; it is also used in
organic synthesis to make nitriles. Potassium carbonate ( or potash)
is used in the manufacture of glass, soap, color TV tubes, fluorescent
lamps, textile dyes and pigments. Potassium permanganate () is an
oxidizing, bleaching and purification substance and is used for
production of saccharin. Potassium chlorate () is added to matches and
explosives. Potassium bromide (KBr) was formerly used as a sedative
and in photography.

While potassium chromate () is used in the manufacture of a host of
different commercial products such as inks, dyes, wood stains (by
reacting with the tannic acid in wood), explosives, fireworks, fly
paper, and safety matches, as well as in the tanning of leather, all
of these uses are due to the chemistry of the chromate ion rather than
to that of the potassium ion.


Niche uses
============
There are thousands of uses of various potassium compounds. One
example is potassium superoxide, , 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.
:

Another example is potassium cobaltinitrite, , which is used as
artist's pigment under the name of Aureolin or Cobalt Yellow.

The stable isotopes of potassium can be laser cooled and used to probe
fundamental and technological problems in quantum physics. The two
bosonic isotopes possess convenient Feshbach resonances to enable
studies requiring tunable interactions, while  is one of only two
stable fermions amongst the alkali metals.


Laboratory uses
=================
An alloy of sodium and potassium, NaK is a liquid used as a
heat-transfer medium and a desiccant for producing dry and air-free
solvents. It can also be used in reactive distillation. The ternary
alloy of 12% Na, 47% K and 41% Cs has the lowest melting point of
−78°C of any metallic compound.

Metallic potassium is used in several types of magnetometers.


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


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


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


Plasma levels
===============
Plasma potassium is normally kept at 3.5 to 5.5 millimoles (mmol) [or
milliequivalents (mEq)] per liter by multiple mechanisms. Levels
outside this range are associated with an increasing rate of death
from multiple causes, and some cardiac, kidney, and lung diseases
progress more rapidly if serum potassium levels are not maintained
within the normal range.

An average meal of 40-50mmol presents the body with more potassium
than is present in all plasma (20-25mmol). This surge causes the
plasma potassium to rise up to 10% before clearance by renal and
extrarenal mechanisms.

Hypokalemia, a deficiency of potassium in the plasma, can be fatal if
severe. Common causes are increased gastrointestinal loss (vomiting,
diarrhea), and increased renal loss (diuresis). Deficiency symptoms
include muscle weakness, paralytic ileus, ECG abnormalities, decreased
reflex response; and in severe cases, respiratory paralysis,
alkalosis, and cardiac arrhythmia.


Control mechanisms
====================
Potassium content in the plasma is tightly controlled by four basic
mechanisms, which have various names and classifications. These are:
# a reactive negative-feedback system,
# a reactive feed-forward system,
# a predictive or circadian system, and
# an internal or cell membrane transport system.
Collectively, the first three are sometimes termed the "external
potassium homeostasis system"; and the first two, the "reactive
potassium homeostasis system".
* The reactive negative-feedback system refers to the system that
induces renal secretion of potassium in response to a rise in the
plasma potassium (potassium ingestion, shift out of cells, or
intravenous infusion.)
* The reactive feed-forward system refers to an incompletely
understood system that induces renal potassium secretion in response
to potassium ingestion prior to any rise in the plasma potassium. This
is probably initiated by gut cell potassium receptors that detect
ingested potassium and trigger vagal afferent signals to the pituitary
gland.
* The ion transport system moves potassium across the cell membrane
using two mechanisms. One is active and pumps sodium out of, and
potassium into, the cell. The other is passive and allows potassium to
leak out of the cell. Potassium and sodium cations influence fluid
distribution between intracellular and extracellular compartments by
osmotic forces. The movement of potassium and sodium through the cell
membrane is mediated by the Na⁺/K⁺-ATPase pump. This ion pump uses ATP
to pump three sodium ions out of the cell and two potassium ions into
the cell, creating an electrochemical gradient and electromotive force
across the cell membrane. The highly selective potassium ion channels
(which are tetramers) are crucial for hyperpolarization inside neurons
after an action potential is triggered, to cite one example. The most
recently discovered potassium ion channel is KirBac3.1, which makes a
total of five potassium ion channels (KcsA, KirBac1.1, KirBac3.1,
KvAP, and MthK) with a determined structure. All five are from
prokaryotic species.


Renal filtration, reabsorption, and excretion
===============================================
Renal handling of potassium is closely connected to sodium handling.
Potassium is the major cation (positive ion) inside animal cells
(150mmol/L, 4.8g/L), while sodium is the major cation of extracellular
fluid (150mmol/L, 3.345g/L). In the kidneys, about 180liters of plasma
is filtered through the glomeruli and into the renal tubules per day.
This filtering involves about 600mg of sodium and 33mg of potassium.
Since only 1-10mg of sodium and 1-4mg of potassium are likely to be
replaced by diet, renal filtering must efficiently reabsorb the
remainder from the plasma.

Sodium is reabsorbed to maintain extracellular volume, osmotic
pressure, and serum sodium concentration within narrow limits.
Potassium is reabsorbed to maintain serum potassium concentration
within narrow limits. Sodium pumps in the renal tubules operate to
reabsorb sodium. Potassium must be conserved, but because the amount
of potassium in the blood plasma is very small and the pool of
potassium in the cells is about 30 times as large, the situation is
not so critical for potassium. Since potassium is moved passively in
counter flow to sodium in response to an apparent (but not actual)
Donnan equilibrium, the urine can never sink below the concentration
of potassium in serum except sometimes by actively excreting water at
the end of the processing. Potassium is excreted twice and reabsorbed
three times before the urine reaches the collecting tubules. At that
point, urine usually has about the same potassium concentration as
plasma. At the end of the processing, potassium is secreted one more
time if the serum levels are too high.

With no potassium intake, it is excreted at about 200mg per day until,
in about a week, potassium in the serum declines to a mildly deficient
level of 3.0-3.5mmol/L. If potassium is still withheld, the
concentration continues to fall until a severe deficiency causes
eventual death.

The potassium moves passively through pores in the cell membrane. When
ions move through ion transporters (pumps) there is a gate in the
pumps on both sides of the cell membrane and only one gate can be open
at once. As a result, approximately 100 ions are forced through per
second. Ion channels have only one gate, and there only one kind of
ion can stream through, at 10 million to 100 million ions per second.
Calcium is required to open the pores, although calcium may work in
reverse by blocking at least one of the pores. Carbonyl groups inside
the pore on the amino acids mimic the water hydration that takes place
in water solution by the nature of the electrostatic charges on four
carbonyl groups inside the pore.


North America
===============
The U.S. National Academy of Medicine (NAM), on behalf of both the
U.S. and Canada, sets Dietary Reference Intakes, including Estimated
Average Requirements (EARs) and Recommended Dietary Allowances (RDAs),
or Adequate Intakes (AIs) for when there is not sufficient information
to set EARs and RDAs.

For both males and females under 9 years of age, the AIs for potassium
are: 400mg of potassium for 0 to 6-month-old infants, 860mg of
potassium for 7 to 12-month-old infants, 2,000mg of potassium for 1 to
3-year-old children, and 2,300mg of potassium for 4 to 8-year-old
children.

For males 9 years of age and older, the AIs for potassium are: 2,500mg
of potassium for 9 to 13-year-old males, 3,000mg of potassium for 14
to 18-year-old males, and 3,400mg for males that are 19 years of age
and older.

For females 9 years of age and older, the AIs for potassium are:
2,300mg of potassium for 9 to 18-year-old females, and 2,600mg of
potassium for females that are 19 years of age and older.

For pregnant and lactating females, the AIs for potassium are: 2,600mg
of potassium for 14 to 18-year-old pregnant females, 2,900mg for
pregnant females that are 19 years of age and older; furthermore,
2,500mg of potassium for 14 to 18-year-old lactating females, and
2,800mg for lactating females that are 19 years of age and older. As
for safety, the NAM also sets tolerable upper intake levels (ULs) for
vitamins and minerals, but for potassium the evidence was
insufficient, so no UL was established.

As of 2004, most Americans adults consume less than 3,000mg.


Europe
========
Likewise, in the European Union, in particular in Germany, and Italy,
insufficient potassium intake is somewhat common.

The National Health Service in the United Kingdom recommends a similar
intake, saying that "adults (19 to 64 years) need  per day" and that
excess amounts may cause health problems such as stomach pain and
diarrhea.


Food sources
==============
Potassium is present in all fruits, vegetables, meat and fish. Foods
with high potassium concentrations include yam, parsley, dried
apricots, milk, chocolate, all nuts (especially almonds and
pistachios), potatoes, bamboo shoots, bananas, avocados, coconut
water, soybeans, and bran.

The  United States Department of Agriculture also lists tomato paste,
orange juice, beet greens, white beans, plantains, and many other
dietary sources of potassium, ranked in descending order according to
potassium content. A day's worth of potassium is in 5 plantains or 11
bananas.


Deficient intake
==================
Mild hypokalemia does not cause distinct symptoms acting instead as a
risk factor for hypertension and cardiac arrhythmia.
Severe hypokalemia usually presents with hypertension, arrhythmia,
muscle cramps, fatigue, weakness and constipation.
Causes of hypokalemia include vomiting, diarrhea, medications like
furosemide and steroids, dialysis, diabetes insipidus,
hyperaldosteronism, hypomagnesemia.


Supplementation
=================
Supplements of potassium are most widely used in conjunction with
diuretics that block reabsorption of sodium and water upstream from
the distal tubule (thiazides and loop diuretics), because this
promotes increased distal tubular potassium secretion, with resultant
increased potassium excretion. A variety of prescription and over-the
counter supplements are available. Potassium chloride may be dissolved
in water, but the salty/bitter taste makes liquid supplements
unpalatable.  Potassium is also available in tablets or capsules,
which are formulated to allow potassium to leach slowly out of a
matrix, since very high concentrations of potassium ion that occur
adjacent to a solid tablet can injure the gastric or intestinal
mucosa. For this reason, non-prescription potassium pills are limited
by law in the US to a maximum of 99mg of potassium.

Potassium supplementation can also be combined with other metabolites,
such as citrate or chloride, to achieve specific clinical effects.

Potassium supplements may be employed to mitigate the impact of
hypertension, thereby reducing cardiovascular risk. Potassium chloride
and potassium bicarbonate may be useful to control mild hypertension.
In 2020, potassium was the 33rd most commonly prescribed medication in
the U.S., with more than 17million prescriptions. Potassium
supplementation has been shown to reduce both systolic and diastolic
blood pressure in individuals with essential hypertension.

Additionally, potassium supplements may be employed with the aim of
preventing the formation of kidney stones, a condition that can lead
to renal complications if left untreated. Low potassium levels can
lead to decreased calcium reabsorption in the kidneys, increasing the
risk of elevated urine calcium and the formation of kidney stones. By
maintaining adequate potassium levels, this risk can be reduced.

The mechanism of action of potassium involves various types of
transporters and channels that facilitate its movement across cell
membranes. This process can lead to an increase in the pumping of
hydrogen ions. This, in turn, can escalate the production of gastric
acid, potentially contributing to the development of gastric ulcers.

Potassium has a role in bone health. It contributes to the acid-base
equilibrium in the body and helps protect bone tissue. Potassium salts
produce an alkaline component that can aid in maintaining bone health.

For individuals with diabetes, potassium supplementation may be
necessary, particularly for those with type 2 diabetes. Potassium is
essential for the secretion of insulin by pancreatic beta cells, which
helps regulate glucose levels. Without sufficient potassium, insulin
secretion is compromised, leading to hyperglycemia and worsening
diabetes.

Excessive potassium intake can have adverse effects, such as
gastrointestinal discomfort and disturbances in heart rhythm.

Potassium supplementation can have side effects on ulceration,
particularly in relation to peptic ulcer disease. Potassium channels
have the potential to increase gastric acid secretion, which can lead
to an increased risk of ulcerations. Medications used for peptic ulcer
disease, known as "proton pump inhibitors", work by inhibiting
potassium pumps that activate the H/K ATPase. This inhibition helps to
reduce the secretion of hydrochloric acid into the parietal cell,
thereby decreasing acidic synthesis and lowering the risk of ulcers.
Nicorandil, a drug used for the treatment of ischemic heart disease,
can stimulate nitrate and potassium ATP channels, and as a result, it
has been associated with side effects such as GI, oral, and anal
ulcers. Potassium chloride tablets are specifically associated with
pill esophagitis. Prolonged and chronic use of potassium supplements
has been linked to more severe side effects, including ulcers outside
of the gastrointestinal (GI) tract. Close monitoring is necessary for
patients who are also taking angiotensinogen-converting enzyme
inhibitors, angiotensin receptor blockers, or potassium-sparing
diuretics.


Detection by taste buds
=========================
Potassium can be detected by taste because it triggers three of the
five types of taste sensations, according to concentration. Dilute
solutions of potassium ions taste sweet, allowing moderate
concentrations in milk and juices, while higher concentrations become
increasingly bitter/alkaline, and finally also salty to the taste. The
combined bitterness and saltiness of high-potassium solutions makes
high-dose potassium supplementation by liquid drinks a palatability
challenge. As a food additive, potassium chloride has a salty taste.
People wishing to increase their potassium intake or to decrease their
sodium intake, after checking with a health professional that it is
safe to do so, can substitute potassium chloride for some or all of
the sodium chloride (table salt) used in cooking and at the table.


                            Precautions
======================================================================
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Potassium metal can react violently with water producing KOH and
hydrogen gas.

:


This reaction is exothermic and releases sufficient heat to ignite the
resulting hydrogen in the presence of oxygen. Finely powdered
potassium ignites in air at room temperature. The bulk metal ignites
in air if heated. Because its density is 0.89g/cm3, burning potassium
floats in water that exposes it to atmospheric oxygen. Many common
fire extinguishing agents, including water, either are ineffective or
make a potassium fire worse. Nitrogen, argon, sodium chloride (table
salt), sodium carbonate (soda ash), and silicon dioxide (sand) are
effective if they are dry. Some Class D dry powder extinguishers
designed for metal fires are also effective. These agents deprive the
fire of oxygen and cool the potassium metal.

During storage, potassium forms peroxides and superoxides. These
peroxides may react violently with organic compounds such as oils.
Both peroxides and superoxides may react explosively with metallic
potassium.

Because potassium reacts with water vapor in the air, it is usually
stored under anhydrous mineral oil or kerosene. Unlike lithium and
sodium, potassium should not be stored under oil for longer than six
months, unless in an inert (oxygen-free) atmosphere, or under vacuum.
After prolonged storage in air dangerous shock-sensitive peroxides can
form on the metal and under the lid of the container, and can detonate
upon opening.

Ingestion of large amounts of potassium compounds, certain drugs, and
homeostatic failure, can lead to hyperkalemia, leading to a variety of
brady- and tachy-arrhythmias that can be fatal. Potassium chloride is
used in the U.S. for lethal injection executions.


                            Bibliography
======================================================================
*
*
*
*
* [https://fdc.nal.usda.gov/fdc-app.html#/ National Nutrient Database]
at USDA Website


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=========
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License URL: http://creativecommons.org/licenses/by-sa/3.0/
Original Article: http://en.wikipedia.org/wiki/Potassium