Potassium

It was first isolated from potash, the ashes of plants, from which its name derives.

Potash includes various mined and manufactured salts that contain potassium in water-soluble form.

In the periodic table, potassium is one of the alkali metals, all of which have a single valence electron in the outer electron shell, that is easily removed to create an ion with a positive charge – a cation, that combines with anions to form salts.

The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr).

It is found dissolved in sea water (which is 0.04% potassium by weight ), and occurs in many minerals such as orthoclase, a common constituent of granites and other igneous rocks.

Orthoclase, or orthoclase feldspar (endmember formula KAlSi 3 O 8 ), is an important tectosilicate mineral which forms igneous rock.

Most industrial applications of potassium exploit the high solubility in water of potassium compounds, such as potassium soaps.

Saltwater soap, also called sailors' soap, is a potassium-based soap for use with seawater.

When Humphry Davy first isolated the pure element using electrolysis in 1807, he named it potassium, which he derived from the word potash.

Sir Humphry Davy, 1st Baronet (17 December 1778 – 29 May 1829) was a Cornish chemist and inventor, who is best remembered today for isolating, using electricity, a series of elements for the first time: potassium and sodium in 1807 and calcium, strontium, barium, magnesium and boron the following year, as well as discovering the elemental nature of chlorine and iodine.

Potassium is a chemical element with the symbol K (from Neo-Latin kalium) and atomic number19.

Naturally occurring potassium is composed of three isotopes, of which [[potassium-40|]] is radioactive.

Potassium-40 ( 40 K) is a radioactive isotope of potassium which has a long half-life of 1.251 years.

Potassium is chemically very similar to sodium, the previous element in group 1 of the periodic table.

By means of the sodium-potassium pump, living human cells pump three sodium ions out of the cell in exchange for two potassium ions pumped in; comparing ion concentrations across the cell membrane, inside to outside, potassium measures about 40:1, and sodium, about 1:10.

With water potassium forms potassium hydroxide.

Potassium hydroxide is an inorganic compound with the formula KOH, and is commonly called caustic potash.

It is found dissolved in sea water (which is 0.04% potassium by weight ), and occurs in many minerals such as orthoclase, a common constituent of granites and other igneous rocks.

Two-mica granites are typically high in potassium and low in plagioclase, and are usually S-type granites or A-type granites.

Three oxides of potassium are well studied: potassium oxide (K 2 O), potassium peroxide (K 2 O 2 ), and potassium superoxide (KO 2 ).

Potassium oxide (KO) or Kalium oxide is an ionic compound of potassium and oxygen.

KOH reacts readily with carbon dioxide to produce potassium carbonate and in principle could be used to remove traces of the gas from air.

Potassium carbonate is the inorganic compound with the formula K 2 CO 3.

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 to call kali.

Leucite is a rock-forming mineral composed of potassium and aluminium tectosilicate K[AlSi 2 O 6 ].

Potassium is the second least dense metal after lithium.

Lithium can float on the lightest hydrocarbon oils and is one of only three metals that can float on water, the other two being sodium and potassium.

When Humphry Davy first isolated the pure element using electrolysis in 1807, he named it potassium, which he derived from the word potash. It was suspected in 1702 that they were distinct elements that combine with the same anions to make similar salts, and was proven in 1807 using electrolysis.

Because of this, potassium and the liquid sodium-potassium (NaK) alloy are potent desiccants, although they are no longer used as such.

Sodium-potassium alloy, colloquially called NaK (commonly pronounced ), is an alloy of two alkali metals, sodium (Na, atomic number 11) and potassium (K, atomic number 19), and which is usually liquid at room temperature.

Most industrial applications of potassium exploit the high solubility in water of potassium compounds, such as potassium soaps.

Sodium soaps, prepared from sodium hydroxide, are firm, whereas potassium soaps, derived from potassium hydroxide, are softer or often liquid.

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.

Feldspars (KAlSi 3 O 8 – NaAlSi 3 O 8 – CaAl 2 Si 2 O 8 ) are a group of rock-forming tectosilicate minerals that make up about 41% of the Earth's continental crust by weight.

Three oxides of potassium are well studied: potassium oxide (K 2 O), potassium peroxide (K 2 O 2 ), and potassium superoxide (KO 2 ). Potassium metal reacts rapidly with atmospheric oxygen to form flaky white potassium peroxide in only seconds of exposure.

It is formed as potassium reacts with oxygen in the air, along with potassium oxide (K 2 O) and potassium superoxide (KO 2 ).

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.

Muscovite (also known as common mica, isinglass, or potash mica ) is a hydrated phyllosilicate mineral of aluminium and potassium with formula KAl 2 (AlSi 3 O 10 )(FOH) 2, or (KF) 2 (Al 2 O 3 ) 3 (SiO 2 ) 6 (H 2 O).

Potassium intercalates into graphite to give a variety of compounds, including KC8.

One of the best studied graphite intercalation compounds, KC 8, is prepared by melting potassium over graphite powder.

The "Gold Book" of the International Union of Pure and Applied Chemistry has designated the official chemical symbol as K.

It is found dissolved in sea water (which is 0.04% potassium by weight ), and occurs in many minerals such as orthoclase, a common constituent of granites and other igneous rocks.

These eight elements, summing to over 98% of the crust by weight, are, in order of decreasing abundance: oxygen, silicon, aluminium, iron, magnesium, calcium, sodium and potassium.

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.

Potassium chloride (also known as KCl or potassium salt) is a metal halide salt composed of potassium and chlorine.

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.

It is based on measurement of the product of the radioactive decay of an isotope of potassium (K) into argon (Ar).