Editing Potassium (section)

===Metal===
[[File:Sir Humphry Davy, Bt by Thomas Phillips.jpg|thumb|[[Humphry Davy|Sir Humphry Davy]] ]]
[[File:Potassium.JPG|thumb|upright|left|Pieces of potassium 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.<ref name="Enghag2004">{{cite book|last=Enghag|first= P.|date=2004|url=https://archive.org/details/encyclopediaofel0000engh| title=Encyclopedia of the elements| publisher=Wiley-VCH Weinheim| isbn=978-3-527-30666-4| chapter=11. Sodium and Potassium}}</ref> 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.<ref name="weeks" /><ref name="disco" /><ref name="Davy1807">{{cite journal|first=Humphry|last=Davy|title=On some new phenomena of chemical changes produced by electricity, in particular the decomposition of the fixed alkalies, and the exhibition of the new substances that constitute their bases; and on the general nature of alkaline bodies|pages=1–44|year=1808|volume=98|journal=Philosophical Transactions of the Royal Society|url=https://books.google.com/books?id=gpwEAAAAYAAJ&pg=PA57|doi=10.1098/rstl.1808.0001|doi-access=free}}</ref><ref name="200disco">{{cite journal|doi = 10.1134/S1061934807110160|title = History of the discovery of potassium and sodium (on the 200th anniversary of the discovery of potassium and sodium)|year = 2007|last1 = Shaposhnik|first1 = V. A.|journal = Journal of Analytical Chemistry|volume = 62|issue = 11|pages = 1100–2|s2cid = 96141217}}</ref> 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.<ref name="disco" />

Because of the sensitivity of potassium to water and air, [[air-free technique]]s are normally employed for handling the element. It is unreactive toward nitrogen and saturated hydrocarbons such as mineral oil or [[kerosene]].<ref name="HollemanAF">{{cite book|publisher = Walter de Gruyter|date = 1985|edition = 91–100|isbn = 978-3-11-007511-3|title = Lehrbuch der Anorganischen Chemie|first1 = Arnold F.|last1 = Holleman|last2 = Wiberg|first2 = Egon|last3 = Wiberg|first3 = Nils|chapter = Potassium| language = de}}</ref> It readily dissolves in liquid [[ammonia]], up to 480 g per 1000 g of ammonia at 0{{nbsp}}°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|{{chem|KNH|2}}]], but this reaction is accelerated by minute amounts of transition metal salts.<ref name="b32">[[#Burkhardt|Burkhardt]], p. 32</ref> 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 metal|Rieke method]].<ref>{{cite journal| author=Rieke, R. D.|title=Preparation of Organometallic Compounds from Highly Reactive Metal Powders|journal= [[Science (journal)|Science]]|year= 1989|volume= 246| pages= 1260–4|doi=10.1126/science.246.4935.1260| pmid=17832221| issue=4935|bibcode = 1989Sci...246.1260R |s2cid=92794}}</ref> Illustrative is the preparation of magnesium:

:{{chem2|[[Magnesium chloride|MgCl2]] + 2 K → Mg + 2 KCl}}