Editing Cobalt(II) chloride (section)

==Properties==
===Anhydrous===
At room temperature, anhydrous cobalt chloride has the [[cadmium chloride]] structure ({{chem|CdCl|2}}) (R{{overline|3}}m) in which the cobalt(II) ions are octahedrally coordinated. At about 706&nbsp;°C (20 degrees below the melting point), the [[Coordination complex|coordination]] is believed to change to tetrahedral.<ref name=wojak/> The vapor pressure has been reported as 7.6&nbsp;[[millimeter of mercury|mmHg]] at the melting point.<ref name=saeki>Yuzo Saeki, Ryoko Matsuzaki, Naomi Aoyama (1977): "The vapor pressure of cobalt dichloride". ''Journal of the Less Common Metals'', volume 55, issue 2, pages 289-291. {{doi|10.1016/0022-5088(77)90204-1}}</ref>

===Solutions===
Cobalt chloride is fairly [[Solubility|soluble]] in water.  Under atmospheric pressure, the [[mass concentration (chemistry)|mass concentration]] of a [[saturated solution]] of {{chem|CoCl|2}} in water is about 54% at the boiling point, 120.2&nbsp;°C; 48% at 51.25&nbsp;°C; 35% at 25&nbsp;°C; 33% at 0&nbsp;°C; and 29% at −27.8&nbsp;°C.<ref name=saugier/>

Diluted [[aqueous]] solutions of {{chem|CoCl|2}} contain the species {{chem|[|Co|(|H|2|O|)|6|]|2+}}, besides [[chloride]] ions.  Concentrated solutions are red at room temperature but become blue at higher temperatures.<ref>''The Merck Index'', 7th edition, Merck & Co, Rahway, New Jersey, USA, 1960.</ref>

===Hydrates===
The crystal unit of the solid hexahydrate {{chem|CoCl|2}}•6{{chem|H|2|O}} contains the neutral molecule ''trans''-{{chem|CoCl|2|(|H|2|O|)|4}} and two molecules of [[water of crystallization]].<ref>{{Wells5th}}</ref> This species dissolves readily in water and [[ethanol|alcohol]].

The anhydrous salt is [[hygroscopic]] and the hexahydrate is [[deliquescent]].{{citation needed|date=February 2019}} The dihydrate, CoCl<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>, is a [[coordination polymer]].  Each Co center is coordinated to four doubly [[bridging chloride ligand]]s.  The octahedron is completed by a pair of mutually trans [[aquo ligand]]s.<ref>{{cite journal |title=Crystal structures of manganese(II) and iron(II) chloride dihydrate |author1=Morosin, B. |author2=Graeber, E. J. |journal=Journal of Chemical Physics |year=1965 |volume=42 |issue=3 |pages=898–901 |doi=10.1063/1.1696078 |bibcode=1965JChPh..42..898M}}</ref>
{{multiple image
 | align = center
 | width = 200
 | footer = Structures of the forms of cobalt(II) chloride 
 | image1 = Cobalt(II)-chloride-3D-balls.png
 | alt1 = 
 | caption1 = Anhydrous
 | image2 = MX2(H2O)2.png
 | alt2 = 
 | caption2 = Dihydrate
 | image3 = MCl2(aq)6forFeCoNi.png
 | alt3 = 
 | caption3 = Hexahydrate}}