Editing Potassium hydroxide (section)

==Properties and structure==
KOH exhibits high [[thermal stability]]. Because of this high stability and relatively low [[melting point]], it is often melt-cast as pellets or rods, forms that have low surface area and convenient handling properties. These pellets become tacky in air because KOH is [[hygroscopic]]. Most commercial samples are ca. 90% pure, the remainder being water and carbonates.<ref name=Ullmann/> Its [[solvation|dissolution]] in water is strongly [[exothermic]]. Concentrated aqueous solutions are sometimes called potassium [[lye]]s. Even at high temperatures, solid KOH does not dehydrate readily.<ref>{{cite book|last1=Holleman|first1=A. F|last2=Wiberg|first2=E. |title=Inorganic Chemistry |publisher=Academic Press|location=San Diego|year=2001|isbn=978-0-12-352651-9}}</ref>

===Structure===
At higher temperatures, solid KOH [[crystallization|crystallizes]] in the [[NaCl]] [[crystal structure]]. The {{OH-}} group is either rapidly or randomly disordered so that it is effectively a spherical [[anion]] of radius 1.53 Å (between {{chem2|Cl-}} and {{chem2|F-}} in size). At room temperature, the {{chem2|OH-}} groups are ordered and the environment about the {{chem2|K+}} centers is distorted, with {{chem2|K+\sOH-}} distances ranging from 2.69 to 3.15 Å, depending on the orientation of the OH group. KOH forms a series of crystalline [[hydrate]]s, namely the monohydrate {{chem2|KOH * [[H2O]]}}, the dihydrate {{chem2|KOH * 2[[H2O]]}} and the tetrahydrate {{chem2|KOH * 4[[H2O]]}}.<ref>{{cite book |last=Wells |first=A.F. |year=1984 |title=Structural Inorganic Chemistry |location=Oxford |publisher=Clarendon Press |isbn=978-0-19-855370-0}}</ref>