The monohydrate and the anhydrous forms can be obtained by cooling solutions only under high pressure, above 206 ☌ and 335 ☌, respectively. Water ice, rather than cobalt chloride, will crystallize from solutions with concentration below 29%. Cooling saturated aqueous solutions yields the dihydrate between 120.2 ☌ and 51.25 ☌, and the hexahydrate below 51.25 ☌. The solid dihydrate and hexahydrate can be obtained by evaporation. Preparation Ĭobalt chloride can be prepared in aqueous solution from cobalt(II) hydroxide or cobalt(II) carbonate and hydrochloric acid: The octahedron is completed by a pair of mutually trans aquo ligands. Each Co center is coordinated to four doubly bridging chloride ligands. The dihydrate, CoCl 2(H 2O) 2, is a coordination polymer. The anhydrous salt is hygroscopic and the hexahydrate is deliquescent. This species dissolves readily in water and alcohol. The crystal unit of the solid hexahydrate CoClĢO contains the neutral molecule trans- CoClĤ and two molecules of water of crystallization. Hydrates Subunit of CoCl 2(H 2O) 2 lattice. Concentrated solutions are red at room temperature but become blue at higher temperatures. Under atmospheric pressure, the mass concentration of a saturated solution of CoClĢ in water is about 54% at the boiling point, 120.2 ☌ 48% at 51.25 ☌ 35% at 25 ☌ 33% at 0 ☌ and 29% at −27.8 ☌. Solutions Ĭobalt chloride is fairly soluble in water. The vapor pressure has been reported as 7.6 mmHg at the melting point. At about 706 ☌ (20 degrees below the melting point), the coordination is believed to change to tetrahedral. Properties Anhydrous Īt room temperature, anhydrous cobalt chloride has the cadmium chloride structure ( CdClĢ) (R 3m) in which the cobalt(II) ions are octahedrally coordinated. Commercial samples are usually the hexahydrate, which is one of the most commonly used cobalt compounds in the lab. The anhydrous form is a blue crystalline solid the dihydrate is purple and the hexahydrate is pink. Claims of the formation of tri- and tetrahydrates have not been confirmed. The compound forms several hydrates CoClĢO, for n = 1, 2, 6, and 9. Cobalt(II) chloride is an inorganic compound of cobalt and chlorine, with the formula CoClĢ.
0 kommentar(er)
