| Uses | Cobalt(II) chloride has several applications. It is used in hygrometers; as a
humidity indicator; as a temperature indicator in grinding; as a foam stabilizer in beer; in invisible ink; for painting on glass; in electroplating; and a catalyst in Grignard reactions, promoting coupling with an organic halide. It also is used to prepare several other cobalt salts; and in the manufacture of synthetic vitamin B12.
The vapor-phase co-reductions with other metal halides by hydrogen results in finely divided intermetallics with applications as structural materials or compounds with useful thermoelectric, magnetic, and oxidation-resistance properties. |
| Preparation | Cobalt(II) chloride is prepared by the action of cobalt metal or its oxide, hydroxide, or carbonate with hydrochloric acid:
Co(OH)2 + 2HCl → CoCl2 + 2H2O
The solution on concentration and cooling forms crystals of hexahydrate which on heating with SOCl2 dehydrates to anhydrous cobalt(II) chloride.
Alternatively, the hexahydrate may be converted to anhydrous CoCl2 by dehydration in a stream of hydrogen chloride and dried in vacuum at 100–150°C.
The anhydrous compound also may be obtained by passing chlorine over cobalt powder. |
| Description | blue crystals (anhydrous)
violet-blue (dihydrate)
rose red crystals (hexahydrate)
Sinks and mixes with water. Pale blue leaflets, turns pink upon exposure to moist air. |
| Chemical Properties | (1) Blue, (2) ruby-red crystals.Soluble in water, alcohol, and acetone. |
| Physical properties | Blue leaflets; turns pink in moist air; hygroscopic; the dihydrate is violet blue crystal; the hexahydrate is pink monoclinic crystal; density 3.36, 2.48 and 1.92 g/cm3 for anhydrous salt, dihydrate and hexahydrate, respectively; anhydrous salt melts at 740°C and vaporizes at 1,049°C; vapor pressure 60 torr at 801°C; the hexahydrate decomposes at 87°C; the anhydrous salt and the hydrates are all soluble in water, ethanol, acetone, and ether; the solubility of hydrates in water is greater than the anhydrous salt. |
| Uses | Cobalt(II) chloride is used in humidity indicator in weather instruments. In the anhydrous form, it finds use in electroplating of cobalt, in organic chemistry and is a precursor to cobaltocene, (bis(cyclopentadienyl)cobalt(II), which is a good reducing agent. It also serves as a Lewis acid. Cobalt chloride is an indicator for water in desiccants, owing to the reversible hydration/dehydration coupled with distinct color change. Cobalt chloride is useful for producing invisible ink as it turns blue when heated and becomes invisible once it gets cooled. Cobalt(II) chloride catalyzes cross coupling of aryl halides or vinyl halides with aryl grignard reagents in excellent yields. |
| Uses | Cobalt chloride (CoCl2) is used to manufacture vitamin B12, even though the compound itself can cause damage to red blood cells. It is also used as a dye mordant (to fix the dye to the textile so that it will not run). It is also of use in manufacturing solid lubricants, as an additive to fertilizers, as a chemical reagent in laboratories, and as an absorbent in gas masks, electroplating, and the manufacture of vitamin B12. |
| Uses | Absorbent for ammonia, gas masks, electroplating, sympathetic inks, hygrometers, manufacture of vitamin B 12, flux for magnesium refining, solid lubricant, dye mordant, catalyst, barometers, laboratory reagent, fertilizer additive. |
| Definition | ChEBI: A cobalt salt in which the cobalt metal is in the +2 oxidation state and the counter-anion is chloride. It is used as an indicator for water in desiccants. |
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