Calcium chloride, characteristics
Calcium chloride, CaCl2, is a common salt and the compound of calcium and chlorine. It behaves as a typical ionic halide, and is solid at room temperature. It has several common applications such as brine for refrigeration plants, ice and dust control on roads, and in concrete. The anhydrous salt is also widely used as a desiccant, where it will adsorb so much water that it will eventually dissolve in its own crystal lattice water. It can be produced directly from limestone, but large amounts are also produced as a by-product of the Solvay process. Because of its hygroscopic nature, the anhydrous form must be kept in tightly-sealed containers.
Calcium Chloride aggressively absorbs moisture from the air, first causing a swelling of the crystals. If the air is humid enough and the temperature is high enough, the crystals melt and liquid saline solution brine) is formed.
Calcium Chloride desiccants work well over a temperature range from freezing up to 100C or more. At low temperature the salt does not absorb moisture under dry conditions. In practical terms calcium chloride desiccants are effective at Relative Humidity above 20-30%, but are relatively more effective under moist conditions.