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),[10][11] and occurs in many minerals such as orthoclase, a common constituent of granites and other igneous rocks.

[19] The "Gold Book" of the International Union of Pure and Applied Chemistry has designated the official chemical symbol as K.[20] Potassium is the second least dense metal after lithium.

In general, potassium compounds are ionic and, owing to the high hydration energy of the K+ ion, have excellent water solubility.

[36][37] For a long time the only significant applications for potash were the production of glass, bleach, soap and gunpowder as potassium nitrate.

[43][44] 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 slowly reacts with ammonia to form KNH2, but this reaction is accelerated by minute amounts of transition metal salts.

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.

[60] 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.

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.

[69] Potassium sodium tartrate (KNaC4H4O6, Rochelle salt) is a main constituent of some varieties of baking powder; it is also used in the silvering of mirrors.

[73][74] Potassium nitrate (KNO3) 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.

Potassium carbonate (K2CO3 or potash) is used in the manufacture of glass, soap, color TV tubes, fluorescent lamps, textile dyes and pigments.

[14] While potassium chromate (K2CrO4) 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,[76] 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.

One example is potassium superoxide, KO2, an orange solid that acts as a portable source of oxygen and a carbon dioxide absorber.

The two bosonic isotopes possess convenient Feshbach resonances to enable studies requiring tunable interactions, while 40K is one of only two stable fermions amongst the alkali metals.

[81] 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.

[96] Deficiency symptoms include muscle weakness, paralytic ileus, ECG abnormalities, decreased reflex response; and in severe cases, respiratory paralysis, alkalosis, and cardiac arrhythmia.

[113] 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.

[114][115] As of 2004, most Americans adults consume less than 3,000 mg.[116] Likewise, in the European Union, in particular in Germany, and Italy, insufficient potassium intake is somewhat common.

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.

[123] Causes of hypokalemia include vomiting, diarrhea, medications like furosemide and steroids, dialysis, diabetes insipidus, hyperaldosteronism, hypomagnesemia.

[130] 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.

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.

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.

The combined bitterness and saltiness of high-potassium solutions makes high-dose potassium supplementation by liquid drinks a palatability challenge.

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.