Хлорид кальция

Химические свойства

Calcium chloride, CaC12, is colorless deliquescent solid that is soluble in water and ethanol. It is formed from the reaction of calcium carbonate and hydrochloric acid or calcium hydroxide and ammonium chloride. It is used in medicine, as an antifreeze, and as a coagulant.

Физические свойства

White crystal, powder or flake; highly hygroscopic; the compound and its solutions absorb moisture from the air at various rates depending on calcium chloride concentrations, relative humidity and vapor pressure of water in the air, temperature, surface area of exposed material, and the rate of air circulation; at 40% and 95% relative humidity and 25°C, one gram anhydrous calcium chloride may absorb about 1.4 g and 17 g water, respectively. (Shearer, W. L. 1978 . In Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed., vol. 4, pp. 432-6. New York: Wiley Interscience); density 2.15, 2.24, 1.85, 1.83 and 1.71 g/cm3 for the anhydrous salt and its mono-, di-, tetra- and hexahydrates, respectively; anhydrous salts melts at 772°C, while the mono-, di-, tetra- and hexahydrates decompose at 260°, 175°, 45.5° and 30°C, respectively; the anhydrous salt vaporizes at 1,935°C; highly soluble in water, moderate to high solubility in alcohol.
Densities and crystallizing temperatures of commercial calcium chloride solutions (Courtesy Allied Corp.):

Вхождение

Calcium chloride may be found in nature as the mineral tachhydrite, CaCl₂?2MgCl₂?12H₂O. It also is found in other minerals. Its concentration in sea water is about 0.15%.
Calcium chloride has several industrial applications. The major applications of this compound are in deicing of roads, dust control, imparting stability to roads and buildings, and to improve traction in tractor tires. It is mixed with ice to make freezing mixtures. Hexahydrate mixed with crushed ice can lower the temperature of the cooling bath to below -50°C. It also is used as a desiccant for dehydrating gases and liquids. It is added to cement in various proportions to manufacture different types of concrete. Other uses are in adhesives, to lower gel temperatures, and as a calcium source in liquid feed supplements for dairy cattle. Also, the compound is used to control particle size development and reduce coalescence in plastics.

Использование

Calcium chloride is highly hygroscopic and is often used as a desiccant.

Подготовка

Calcium chloride is obtained as a by-product in the manufacture of sodium carbonate (soda ash) by ammonia-soda (Solvay) process. The process involves the reaction of sodium chloride with calcium carbonate and ammonia. Calcium chloride is currently produced in bulk amounts by evaporation of natural underground brines. In the laboratory, calcium chloride can be prepared by treating limestone with hydrochloric acid followed by evaporation of solution to obtain crystals. The crystals are dehydrated to obtain anhydrous salt. Calcium oxide or hydroxide may be used instead of carbonate.

Определение

calcium chloride: A white deliquescentcompound, CaCl₂, which issoluble in water; r.d. 2.15; m.p.782°C; b.p. >1600°C. There are anumber of hydrated forms, includingthe monohydrate, CaCl₂.H₂O, the dihydrate,CaCl₂.2H₂O (r.d. 0.84), andthe hexahydrate, CaCl₂.6H₂O (trigonal;r.d. 1.71; the hexahydrate loses4H₂O at 30°C and the remaining2H₂O at 200°C). Large quantities of itare formed as a byproduct of theSolvay process and it can be preparedby dissolving calcium carbonateor calcium oxide in hydrochloricacid. Crystals of the anhydrous saltcan only be obtained if the hydratedsalt is heated in a stream of hydrogenchloride. Solid calcium chloride isused in mines and on roads to reducedust problems, whilst the molten saltis the electrolyte in the extraction ofcalcium. An aqueous solution of calciumchloride is used in refrigerationplants.

Методы производства

Calcium chloride is a principal byproduct from the Solvay process.

Общее описание

Calcium Chloride (CaCl₂) is a water soluble ionic crystal with a high enthalpy change of solution. It is majorly derived from limestone and is a by-product of the Solvay process. It is an anhydrous salt that has a hygroscopic nature and can be used as a desiccant.

Реакции воздуха и воды

Deliquescent. Water soluble. Adding Calcium chloride to hot water caused violent boiling, [MCA Case History No. 69].

Профиль реактивности

Bromine trifluoride rapidly attacks the following salts: barium chloride, cadmium chloride, Calcium chloride, cesium chloride, lithium chloride, silver chloride, rubidium chloride, potassium bromide, potassium chloride, potassium iodide, rhodium tetrabromide, sodium bromide, sodium chloride, and sodium iodide [Mellor 2 Supp. 1:164, 165 1956]. Long term exposure of Calcium chloride solution upon a zinc coated galvanized iron vessel caused slow evolution of hydrogen which ignited and exploded [Bretherick, 5th Ed., 1995].

Угроза здоровью

Inhalation causes irritation of nose and throat. Ingestion causes irritation of mouth and stomach. Contact with eyes (particularly by dust) causes irritation and possible transient corneal injury. Contact of solid with dry skin causes mild irritation; strong solutions can cause marked irritation, even a superficial burn.

Фармацевтические приложения

The main applications of calcium chloride as an excipient relate to its dehydrating properties and, therefore, it has been used as an antimicrobial preservative, as a desiccant, and as an astringent in eye lotions.
Therapeutically, calcium chloride injection 10% (as the dihydrate form) is used to treat hypocalcemia.

Профиль безопасности

Moderately toxic by ingestion. Poison by intravenous, intramuscular, intraperitoneal, and subcutaneous routes. Human systemic effects: dermatitis, changes in calcium. Questionable carcinogen with experimental tumorigenic data. Mutation data reported. Reacts violently with (B203 + CaO), BrF3. Reaction with zinc releases explosive hydrogen gas. Catalyzes exothermic polymerization of methyl vinyl ether. Exothermic reaction with water. When heated to decomposition it emits toxic fumes of Cl-. See also CALCIUM COMPOUNDS and CHLORIDES.

Безопасность

Calcium chloride is used in topical, ophthalmic, and injection preparations. The pure form of calcium chloride is toxic by intravenous, intramuscular, intraperitoneal, and subcutaneous routes, and moderately toxic by ingestion, causing stomach and heart disturbances. It is a severe eye irritant and can cause dermatitis.
LD₅₀ (mouse, IP): 0.21 g/kg
LD₅₀ (mouse, IV): 0.042 g/kg
LD₅₀ (mouse, oral): 1.94 g/kg
LD₅₀ (mouse, SC): 0.82 g/kg
LD₅₀ (rat, IM): 0.025 g/kg
LD₅₀ (rat, IP): 0.26 g/kg
LD₅₀ (rat, oral): 1.0 g/kg
LD₅₀ (rat, SC): 2.63 g/kg

Возможный контакт

Calcium chloride is used as road salt for melting snow, a drying agent in desiccators, for dehydrating organic liquids and gases, in refrigeration brines and antifreeze, as a dust-proofing agent, food additives, concrete hardening accelerator, and others. May react with strong oxidizers.

хранилище

Calcium chloride is chemically stable; however, it should be protected from moisture. Store in airtight containers in a cool, dry place.

Перевозки

There are no label or maximum shipping quantity requirements set by DOT.

Методы очистки

It is available as fused granules or cubic crystals. It is very hygroscopic, very soluble in H2O (exothermic), and EtOH. Store it in a tightly closed container. [Ehrlich in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 931 1963.]

Несовместимости

Calcium chloride is incompatible with soluble carbonates, phosphates, sulfates, and tartrates. It reacts violently with bromine trifluoride, and a reaction with zinc releases explosive hydrogen gas. It has an exothermic reaction with water, and when heated to decomposition it emits toxic fumes of chlorine.

Регуляторный статус

GRAS listed. Included in the FDA Inactive Ingredients Database (injections, ophthalmic preparations, suspensions, creams). Included in medicines licensed in the UK (eye drops; intraocular irrigation; vaccines; injection powders for reconstitution; nebulizer solution; oral suspension).