Neptune's Gift: A History of Common Salt by Robert P. Multhauf (Smithsonian Institution)
This comprehensive history of salt deals with its production, uses, and role in the development of modern society. Today, only about two per cent of salt produced is for animal consumption. Ten times as much is used in the winter salting of roads, and about half of today's enormous production is used in the chemical industries, for the production, among other things, of herbicides, pesticides and other environment-threatening materials.