塩化コバルト(II)

化学的特性Cobalt chloride (CoCl₂) is a purplish-red or red monoclinic crystal that is slightly weathered and easily deliquescent. It has a melting point of 724°C and is soluble in water, ethanol, ether, and acetone. The anhydrous compound has the molecular formula CoCl₂, containing 45.4% cobalt and 54.6% chlorine. The monohydrate compound has the molecular formula CoCl₂·H₂O, containing 39.9% cobalt. The hexahydrate compound has the molecular formula CoCl₂·6H₂O, containing 24.8% cobalt. Cobalt chloride crystals are stable at room temperature but lose water of crystallization and turn blue when heated. They turn red in humid air. When heated or when concentrated hydrochloric acid, chloride, or organic solvents are added, its aqueous solution becomes blue. The compound crystallizes at 30–45°C and begins to weather, becoming turbid. It forms a tetrahydrate when heated at 45–50°C for 4 hours, and becomes anhydrous when heated to 110°C. It is obtained through the reaction of cobalt powder, cobalt oxide, cobalt hydroxide, or cobalt carbonate with hydrochloric acid.

純化方法A saturated aqueous solution at room temperature is fractionally crystallised by standing overnight. The first half of the material that crystallises in this way is used in the next crystallisation. The process is repeated several times, water being removed in a dry-box using air filtered through glass wool and dried over CaCl2 [Hutchinson J Am Chem Soc 76 1022 1954]. It has also been crystallised from dilute aqueous HCl. The hexahydrate m 86o forms pink to red deliquescent crystals. It loses 4H2O on heating at 52-56o and forms the violet dihydrate which loses a further H2O at 100o to form the violet monohydrate which loses the last H2O at 120-140o to give the pale blue anhydrous deliquescent salt m 735o and b 1049o. A pink solution of CoCl2 in H2O becomes blue on heating to 50o or adding conc HCl which may precipitate the mono or dihydrate. The solid dihydrate gives a blue-purple solution with EtOH. Note: CoCl2 in H2O is a “sympathetic ink”, i.e. writing using an aqueous solution is almost invisible on paper, but becomes blue on warming the paper. On cooling or standing, the writing becomes invisible again. The anhydrous salt is soluble in H2O, EtOH, Et2O, Me2CO and pyridine. [Glemser in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol II p 1515 1965.]

定義本品は、コバルトの塩化物であり、次の化学式で表される。

定義ChEBI: Cobalt dichloride is 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. It has a role as a two-colour indicator, an allergen, a calcium channel blocker and a sensitiser. It is a cobalt salt and an inorganic chloride. It contains a cobalt(2+).