Calcium chloride is an inorganic compound, a salt with the chemical formula CaCl2. It is a colorless crystalline solid at room temperature, highly soluble in water.
Calcium chloride is commonly encountered as a hydrated solid. These compounds are mainly used for de-icing and dust control. Because the anhydrous salt is hygroscopic, it is used as a desiccant.
De-icing and freezing point depression
By depressing the freezing point of water, calcium chloride is used to prevent ice formation and is used to de-ice. This application consumes the greatest amount of calcium chloride. Calcium chloride is relatively harmless to plants and soil. As a de-icing agent, it is much more effective at lower temperatures than sodium chloride. When distributed for this use, it usually takes the form of small, white spheres a few millimeters in diameter, called prills. Solutions of calcium chloride can prevent freezing at temperature as low as −52 °C (−62 °F), making it ideal for filling agricultural implement tires as a liquid ballast, aiding traction in cold climates.
It is also used in domestic and industrial chemical air dehumidifiers.
Calcium chloride was sprayed on this road to prevent weathering, giving it a wet appearance even in dry weather.
The second largest application of calcium chloride exploits hygroscopic properties and the tackiness of its hydrates. A concentrated solution keeps a liquid layer on the surface of dirt roads, which suppresses formation of dust. It keeps the finer dust particles on the road, providing a cushioning layer. If these are allowed to blow away, the large aggregate begins to shift around and the road breaks down. Using calcium chloride reduces the need for grading by as much as 50% and the need for fill-in materials as much as 80%.
Calcium chloride is used to increase the water hardness in swimming pools. This process reduces the erosion of the concrete in the pool. By Le Chatelier’s principle and the common ion effect, increasing the concentration of calcium in the water will reduce the dissolution of calcium compounds essential to the structure of concrete.
The average intake of calcium chloride as food additives has been estimated to be 160–345 mg/day. Calcium chloride is permitted as a food additive in the European Union for use as a sequestrant and firming agent with the E number E509. It is considered as generally recognized as safe (GRAS) by the U.S. Food and Drug Administration. Its use in organic crop production is generally prohibited under the US National Organic Program.
As a firming agent, calcium chloride is used in canned vegetables, in firming soybean curds into tofu and in producing a caviar substitute from vegetable or fruit juices. It is commonly used as an electrolyte in sports drinks and other beverages, including bottled water. The extremely salty taste of calcium chloride is used to flavor pickles without increasing the food’s sodium content. Calcium chloride’s freezing-point depression properties are used to slow the freezing of the caramel in caramel-filled chocolate bars. Also, it is frequently added to sliced apples to maintain texture.
In brewing beer, calcium chloride is sometimes used to correct mineral deficiencies in the brewing water. It affects flavor and chemical reactions during the brewing process, and can also affect yeast function during fermentation.
In cheesemaking, calcium chloride is sometimes added to processed (pasteurized/homogenized) milk to restore the natural balance between calcium and protein in casein. It is added before the coagulant.
Calcium chloride is used to prevent cork spot and bitter pit on apples by spraying on the tree during the late growing season.
Laboratory and related drying operations
Drying tubes are frequently packed with calcium chloride. Kelp is dried with calcium chloride for use in producing sodium carbonate. Anhydrous calcium chloride has been approved by the FDA as a packaging aid to ensure dryness (CPG 7117.02).
Aqueous calcium chloride is used in genetic transformation of cells by increasing the cell membrane permeability, inducing competence for DNA uptake (allowing DNA fragments to enter the cell more readily).