History of salt

Salt, NaCl, is an ionic compound made of sodium and chloride ions which has been exceptionally important to humans for thousands of years, because it is one of the substances upon which all of life evolved to depend. Humans, like all life, need a supply of salt in order to simply survive. Salt's ability to preserve food was a foundation of civilization. It helped to eliminate the dependence on the seasonal availability of food and it allowed travel over long distances. However, salt was difficult to obtain, and so it was a highly valued trade item to the point of being considered a form of currency by certain peoples. Many salt roads, such as the via Salaria in Italy, had been established by the Bronze age.