A colorless or white solid, calcium chloride is well known for its anhydrous properties, with the capacity of absorbing more than its own weight of water. The inorganic crystalline compound is commonly employed as a drying agent and is often featured in small packets as packing for moisture-sensitive electronics and other products.

View a second image of crystallized calcium chloride.

As a by-product of the Solvay chemical process for manufacturing sodium carbonate, calcium chloride can also be synthesized directly by reacting hydrochloric acid with calcium carbonate. In addition to its common use as a drying agent, calcium chloride is used in oil and gas drilling, dust control for unpaved roads, road base stabilization, ready-mix concrete acceleration, gas drying, tractor tire weighting, brine refrigeration, food preservation, and an extender for rock salt used for deicing winter roads. For marine aquariums, the high solubility of calcium chloride makes it a great source of calcium for calcifying organisms such as corals and oysters. Safer for freshwater aquatic ecosystems and vegetation than sodium chloride, calcium chloride (in a corrosion-inhibited formulation) can melt ice at temperatures of minus 25 degrees Fahrenheit, well beyond regular salt's range.

Once a waste product, but now marketed under several brand names, calcium chloride has a pH between 8 and 9 when dissolved into aqueous solution, a melting point of 772 degrees Celsius, and a boiling point of more than 1,600 degrees Celsius. Caution is needed in some cases because metals will slowly corrode when exposed to aqueous calcium chloride solutions. In particular, this calcium salt aggressively attacks yellow brass and aluminum and its alloys. As a source of elemental calcium (which does not occur in nature), the electrolysis of molten calcium chloride creates calcium for commercial purposes.

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