Editing Cobalt(II) chloride (section)

==Preparation==
Cobalt chloride can be prepared in aqueous solution from [[cobalt(II) hydroxide]] or [[cobalt(II) carbonate]] and [[hydrochloric acid]]:
:{{chem|CoCO|3}} + 2 HCl<sub>(aq)</sub> → {{chem|CoCl|2}}<sub>(aq)</sub>  +  {{chem|CO|2}}  +  {{chem|H|2|O}}

:{{chem|Co|(|OH|)|2}} + 2 HCl<sub>(aq)</sub>  → {{chem|CoCl|2}}<sub>(aq)</sub>  +  2{{chem|H|2|O}}

The solid dihydrate and hexahydrate can be obtained by evaporation.  Cooling saturated aqueous solutions yields the dihydrate between 120.2&nbsp;°C and 51.25&nbsp;°C, and the hexahydrate below 51.25&nbsp;°C. Water ice, rather than cobalt chloride, will crystallize from solutions with concentration below 29%. The monohydrate and the anhydrous forms can be obtained by cooling solutions only under high pressure, above 206&nbsp;°C and 335&nbsp;°C, respectively.<ref name=saugier/>

The anhydrous compound can be prepared by heating the hydrates.<ref>John Dallas Donaldson, Detmar Beyersmann, "Cobalt and Cobalt Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. {{doi|10.1002/14356007.a07_281.pub2}}</ref>

On rapid heating or in a closed container, each of the 6-, 2-, and 1- hydrates partially melts into a mixture of the next lower hydrate and a saturated solution—at 51.25&nbsp;°C, 206&nbsp;°C, and 335&nbsp;°C, respectively.<ref name=saugier/> On slow heating in an open container, so that the water vapor pressure over the solid is practically zero, water evaporates out of each of the solid 6-, 2-, and 1- hydrates, leaving the next lower hydrate, at about 40°C, 89°C, and 125°C, respectively.  If the partial pressure of the water vapor is in equilibrium with the solid, as in a confined but not pressurized container, the decomposition occurs at about 115°C, 145°C, and 195°C, respectively.<ref name=saugier/>

Dehydration can also be effected with [[trimethylsilyl chloride]]:<ref>{{cite book |chapter=Solvated and Unsolvated Anhydrous Metal Chlorides from Metal Chloride Hydrates |title=Inorganic Syntheses |volume=29 |author1=Philip Boudjouk |author2=Jeung-Ho So|pages=108–111 |doi=10.1002/9780470132609.ch26 |date=2007 |isbn=9780470132609}}</ref>
:{{chem|CoCl|2}}•6{{chem|H|2|O}} + 12 {{chem|(|CH|3|)|3|SiCl}} → {{chem|CoCl|2}} + 6{{chem|[|(|CH|3|)|3|SiCl|]|2|O}} + 12 HCl

The anhydrous compound can be purified by sublimation in vacuum.<ref name=wojak>{{cite journal |author1=Wojakowska, A. |author2=Krzyżak, E. |author3=Plińska, S. |date=2007 |title=Melting and high-temperature solid state transitions in cobalt(II) halides |journal=Journal of Thermal Analysis and Calorimetry |volume=88 |issue=2 |pages=525–530 |doi=10.1007/s10973-006-8000-9}}</ref>