Кобальта хлорид

Описание

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.

Химические свойства

(1) Blue, (2) ruby-red crystals.Soluble in water, alcohol, and acetone.

Физические свойства

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.

Использование

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.

Определение

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.

Общее описание

Cobalt(II) chloride is an anhydrous cobalt salt. Cobalt(II) chloride participates in the synthesis of various esters in the presence of acetonitrile.

Реакции воздуха и воды

Hygroscopic. Soluble in water.

Профиль реактивности

A 0.2 molar aqueous solution has a pH of 4.6. Cobalt chloride acts as a weakly acidic inorganic salt, which is soluble in water. The resulting solutions contain moderate concentrations of hydrogen ions and have pH's of less than 7.0. They react as acids to neutralize bases. These neutralizations generate heat, but less or far less than is generated by neutralization of inorganic acids, inorganic oxoacids, and carboxylic acid. They usually do not react as either oxidizing agents or reducing agents but such behavior is not impossible. Many of these compounds catalyze organic reactions. Potassium or sodium metals act to reduce metal halides, producing exothermic reactions, even explosions [Bretherick, 5th Ed., 1995].

Опасность

May not be used in food products (FDA). Can cause blood damage.

Угроза здоровью

Inhalation causes respiratory disease, shortness of breath, and coughing; permanent disability may occur. Ingestion causes pain, vomiting, and diarrhea. Contact causes irritation of eyes and may cause skin rash.

Пожароопасность

Special Hazards of Combustion Products: Toxic cobalt oxide fumes may form in fire.

Профиль безопасности

Suspected carcinogen with experimental carcinogenic data. Poison experimentally by ingestion, skin contact, intraperitoneal, intravenous, and subcutaneous routes. Moderately toxic to humans by ingestion. Human systemic effects by ingestion: anorexia, goiter (increased thyroid size), and weight loss. Experimental teratogenic and reproductive effects. Human mutation data reported. Incompatible with metals (e.g., sodmm and potassium). See also COBALT. When heated to decomposition it emits toxic fumes of Cl-.

Методы очистки

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.]