The chlorine ion bound with a sodium ion forms the chemical compound sodium chloride (NaCl), known as common table salt. NaCl is chemically composed of 60 percent chlorine, a gas, and 40 percent sodium, a metal. Purity of salt is dependent on its source and its method of production. For instance, mined rock salt typically ranges between 95 percent and 99.9 percent NaCl, and evaporated salt from purified brine is nearly 99.9 percent pure.
Salt is an essential nutrient. Humans and animals need salt for musculature balance, digestion of food, and proper functioning of the nervous system; salt is lost daily through urination and perspiration. The human body contains about eight ounces of salt. If salt is not replaced, our bodies try to gain an optimum saline balance by discharging excess water. A specific hunger for salt can arise in extreme cases of sodium loss or deprivation. Meanwhile, the presence of too much salt in the diet is thought to be a contributing factor for high blood pressure.