Chemically, salt is a mineral called "Sodium Chloride" (NaCl). Commonly called edible salt, table salt or just salt, it is one of a very few rocks commonly eaten by humans. There are different forms of edible salt: unrefined salt, refined salt, table salt or iodized salt. Salt is a crystalline solid, white in color, obtained from seawater or rock deposits. Sea salt comes in fine or larger crystals. As found in nature, it includes not only sodium chloride, but also other vital trace minerals. Salt flavor is one of the basic tastes.

Salt is essential for life and for good health. The sodium it contains helps maintain the fluid in our blood cells and transmit electrical impulses between our brain, nerves and muscles. Iodized table salt has significantly reduced disorders of iodine deficiency in countries where it is used. Iodine is important to prevent the insufficient production of thyroid hormones (hypothyroidism), which can cause goiter, cretinism and myxedema. Over consumption however, can also cause health problems, including high blood pressure.

History of Salt

Salt was in general use long before history, as we know it, began to be recorded. A Chinese treatise on pharmacology- Peng-Tzao-Kan-Mu- dating some 2,700 years B.C. is probably the earliest known records. This work mentions 40 kinds of salt, including descriptions of two methods of extracting salt and putting it in usable form that are amazingly similar to processes used today.

The preservative ability of salt is in a way the foundation of civilization. It eliminated dependency of man on the seasonal availability of food, allowed travel over long distances, and was a vital food additive.

However, because salt in the ancient times was difficult to obtain, it became a highly valued trade item throughout history. Until the 1900s, salt was one of the prime movers of national economies and wars. Realizing that everyone needed to consume salt, governments tried to create salt monopoly. Salt was often taxed; research has discovered this practice to have existed as early as the 20th century BC in China.

In ancient times Roman soldiers were paid their salaries in the form of salt. The word soldier comes from the Roman word saldare. It means to give salt. The Latin word salarium too means salt money. From the Latin "sal," for example, come such other derived words as "sauce" and "sausage."

Salt was of crucial importance economically. Interesting anecdotes from history make us realize this.

In ancient Greece, a system of trade involved the exchange of salt for slaves which gave rise to the expression, "not worth his salt." In India "aapka namak khaya hai" is a phrase indicating one's loyalty.

In the Mali Empire, merchants in 12th century Timbuktu valued salt enough to buy it for its weight in gold. The Venetian traveler Marco Polo who journeyed to China noticed that the people of Tibet used packets of salt as money. These packets bore the seal of the powerful Mongol ruler Kublai Khan, who then ruled China.

Under the rule of the first great empire in India of the Mauryas more than 2000 years ago, salt could be produced only by the ruler. Not only that, those who sold salt had to pay four different taxes. And those who bought salt had to pay two taxes on its purchase.

Tribes often exchanged their goods for salt from the people living in towns. It was an important trading commodity carried by explorers.

Making Salt

The manufacture and use of salt is one of the oldest chemical industries. Today, most refined salt is prepared from rock salt: mineral deposits high in edible salt. These rock salt deposits were formed by the evaporation of ancient salt lakes. These deposits may be mined conventionally or through the injection of water. Injected water dissolves the salt, and the brine solution can be pumped to the surface where the salt is collected. It is then purified according to need.

Only about 7% of refined salt is used as a food additive. The majority is used for industrial purposes like manufacturing pulp and paper, setting dyes in textiles and fabric, producing soaps and detergents and de-icing roads, and has great commercial value. In India, seawater is the main source of salt. Salt is also made from several salt lakes such as the Sambar Lake in Rajasthan, Chilka Lake in Orissa; salt springs in the Rann of Kutch, the Manekudi Lake in Kerala and the Vedaranyam swamp in Tamil Nadu.