Editing Potassium (section)

===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 heap]]s. 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.<ref name="indus" />

Pure potassium metal can be isolated by electrolysis of its [[potassium hydroxide|hydroxide]] in a process that has changed little since it was first used by Humphry Davy in 1807. Although the electrolysis process was developed and used in industrial scale in the 1920s, the thermal method by reacting sodium with [[potassium chloride]] in a chemical equilibrium reaction became the dominant method in the 1950s.
:Na + KCl → NaCl + K
The production of [[NaK|sodium potassium alloys]] is accomplished by changing the reaction time and the amount of sodium used in the reaction. The Griesheimer process employing the reaction of [[potassium fluoride]] with [[calcium carbide]] was also used to produce potassium.<ref name="indus" /><ref>{{cite book|doi=10.1002/0471238961.1615200103080921.a01.pub2|isbn= 978-0-471-23896-6
|last1=Chiu|first1=Kuen-Wai
|publisher=John Wiley & Sons, Inc.
|title=Kirk-Othmer Encyclopedia of Chemical Technology
|date=2000
|chapter= Potassium
}}</ref>

:{{chem2|2 KF + CaC2 → 2 K + CaF2 + 2 C}}

[[reagent|Reagent-grade]] potassium metal costs about $10.00/[[pound (mass)|pound]] ($22/[[kg]]) in 2010 when purchased by the [[tonne]]. Lower purity metal is considerably cheaper. The market is volatile because long-term storage of the metal is difficult. It must be stored in a dry [[inert gas]] atmosphere or [[anhydrous]] [[mineral oil]] to prevent the formation of a surface layer of [[potassium superoxide]], a pressure-sensitive [[explosive]] that [[Detonation|detonates]] when scratched. The resulting explosion often starts a fire difficult to extinguish.<ref>[[#Burkhardt|Burkhardt]], p. 34</ref><ref name="fire">{{cite journal|doi =10.1016/j.jchas.2006.09.010|title =Review of the safety of potassium and potassium oxides, including deactivation by introduction into water|year =2007|last1 =Delahunt|first1 = J.|last2 =Lindeman|first2 = T.|journal =Journal of Chemical Health and Safety|volume =14|issue =2|pages =21–32}}</ref><!--Kilogram quantities of potassium cost far more, in the range of $700/kg. This is partially due to the cost of [[hazardous material]] shipping requirements.-->