<Table> <Tr> <Td> </Td> <Td> The examples and perspective in this article deal primarily with England and the Anglophone world and do not represent a worldwide view of the subject . You may improve this article, discuss the issue on the talk page, or create a new article, as appropriate . (May 2011) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> The examples and perspective in this article deal primarily with England and the Anglophone world and do not represent a worldwide view of the subject . You may improve this article, discuss the issue on the talk page, or create a new article, as appropriate . (May 2011) (Learn how and when to remove this template message) </Td> </Tr> <P> Salt, also referred to as table salt or by its chemical formula NaCl, is an ionic compound made of sodium and chloride ions . All life has evolved to depend on its chemical properties to survive . It has been used by humans for thousands of years, from food preservation to seasoning . Salt's ability to preserve food was a founding contributor to the development of civilization . It helped to eliminate dependence on seasonal availability of food, and made it possible to transport food over large distances . However, salt was often difficult to obtain, so it was a highly valued trade item, and was 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 . </P> <P> All through history, availability of salt has been pivotal to civilization . In Britain, the suffix "- wich" in a placename means it was once a source of salt, as in Sandwich and Norwich . The Natron Valley was a key region that supported the Egyptian Empire to its north, because it supplied it with a kind of salt that came to be called by its name, natron . Today, salt is almost universally accessible, relatively cheap, and often iodized . There have been reports as to the value of salt in historical times, however it has never been more valuable than gold . </P>

When was salt first used as a preservative