The other two water molecules are not bonded directly to cobalt. 12 ?) and by two chlorine atoms (Co-Cl = 2.43 ?) to form a distorted octahedron. The hexahydrate COCl2.6H2O forms monoclinic crystals in which each cobalt atom is surrounded by four water molecules at the corners of a distorted square (Co-H20 =. The anhydrous salt is soluble in H2O, EtOH, Et2O, Me2CO and pyridine. On cooling or standing, the writing becomes invisible again. writing using an aqueous solution is almost invisible on paper, but becomes blue on warming the paper. Note: CoCl2 in H2O is a “sympathetic ink”, i.e. The solid dihydrate gives a blue-purple solution with EtOH. The hexahydrate m 86o forms pink to red deliquescent crystals.Ĭobalt chloride hexahydrateloses 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.Ī pink solution of CoCl2 in H2O becomes blue on heating to 50o or adding conc HCl which may precipitate the mono or dihydrate. The process is repeated several times, water being removed in a dry-box using air filtered through glass wool and dried over CaCl2.Ĭobalt chloride hexahydratehas also been crystallised from dilute aqueous HCl. The first half of the material that crystallises in this way is used in the next crystallisation. While cobalt(II) fluoride is the product of the reaction of anhydrous cobalt(II) chloride with hydrofluoric acid, cobalt(III) fluoride is obtained from fluorination of an aqueous solution of cobalt(II) chloride.Īddition of potassium nitrite, KNO2 to a solution of cobalt(II) chloride yields yellow crystalline potassium hexanitrocobaltate(III), K3Co(NO2)6.Ĭobalt chloride hexahydrate can be used as an inducer of HIF-1 production used to study apoptotic effects in HepG2 cells.Ĭobalt chloride hexahydrate can be used as Invisible ink humidity and water indicator in hygrometers tempereture indicator in grinding in electroplating for painting on glass and porcelain preparation of catalysts fertilizer and feed additive foam stabilizer in beer as absorbent for military poison gas and ammonia in manufacture of vitamin B12.ĬhEBI: A hydrate of cobalt chloride containing cobalt (in +2 oxidation state), chloride and water moieties in the ratio 1:2:6.Ī saturated aqueous solution at room temperature is fractionally crystallised by standing overnight. Reaction with ammonium hydrogen phosphate yields cobalt(II) phosphate:ģCoCl2 + 2(NH4)2HPO4 → Co3(PO4)2 +4NH4Cl + 2HCl Reaction with alkali hydroxide produces cobalt(II) hydroxide: The anhydrous compound also may be obtained by passing chlorine over cobalt powder.Ĭobalt chloride hexahydrate undergoes many double decomposition reactions in aqueous solution to produce precipitates of insoluble cobalt salts.įor example, heating its solution with sodium carbonate yields cobalt(II) carbonate: The solution on concentration and cooling forms crystals of hexahydrate which on heating with SOCl2 dehydrates to anhydrous Cobalt chloride hexahydrate.Īlternatively, the hexahydrate may be converted to anhydrous CoCl2 by dehydration in a stream of hydrogen chloride and dried in vacuum at 100–150☌. 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☌ and vaporizes at 1,049☌ vapor pressure 60 torr at 801☌ the hexahydrate decomposes at 87☌ 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.Ĭobalt chloride hexahydrate has several applications.Ĭobalt chloride hexahydrate 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.Ĭobalt chloride hexahydrate also is used to prepare several other cobalt salts and in the manufacture of synthetic vitamin B12.Ĭobalt chloride hexahydrate is prepared by the action of cobalt metal or its oxide, hydroxide, or carbonate with hydrochloric acid:
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