For the sake of salt, Rome created a system of remuneration (from which we get the word salary), nomads domesticated the camel, the Low Countries revolted against their Spanish oppressors, and Gandhi marched against the British. Through the ages, salt has conferred status, preserved foods, and mingled in the blood, sweat, and tears of humankind. Today, chefs of haute cuisine covet its most exotic forms -- underground salt deposits, Hawaiian black...