Since the earliest times it has been used to flavour and preserve food. The chemical industry uses it to make chlorine and caustic soda.
Quentin Coopertalks to
Professor Graham MacGregor and DrJim Thomas about the physics and chemistry of salt. Championed for preventing iodine deficiency disorders and cited as a cause of high blood pressure, salt remains a controversial but indispensable part of our lives. Producer John Watkins. E-MAIL: material.world@bbc.co.uk