WHAT IS IT?

Spill some, and you'll probably throw a pinch of it over your shoulder to ward off bad luck. In parts of Africa, 23 Kg (50 pounds) of it is enough to get you a wife. Lack of it lost Napoleon an empire. Escoffier himself couldn't cook without it. A major meat packer uses 31.5 t (35 tons) of it a day. For centuries, it has been one of the most valuable substances known to man. You probably know it as common table salt. But just what is that white stuff in your salt shaker?

Salt is a mineral composed of sodium and chlorine. Neither can exist alone in natural form. Together, they form the stable chemical compound that is sodium chloride, or salt. To geologists, salt is known as halite, from "hals", the Greek word for salt. Halite belongs to the family of minerals which are compounds of the metals with the halogen elements fluorine, chlorine, bromine, and iodine.

Salt is a crystal of the isometric system, which means it is usually cubic and perfectly symmetrical. Pure salt crystals are colourless, although a pile of them will appear white. Impure crystals may be various shades of yellow, red, blue or purple. Salt is one of the earth's most abundant minerals. The world's oceans alone contain an estimated 18,756,000 Km3 (4,500,000 cubic miles) of salt, or enough to cover the entire surface of the globe to a depth of 122 m (400 feet). Millions of tons of salt are extracted each year from the sea and underground deposits.

Salt is such a basic commodity and is used in so many different ways that a chart of salt consumption is almost a barometer of economic conditions. From such charts, economists can trace the rise and fall of national prosperity.

Today, we can find over 14,000 uses for salt in industry, in medicine and in the home. In addition to its direct use in industry, salt plays a vital role as a raw material in the manufacture of other chemicals. Farmers depend on it to keep their stock healthy. Salt adds flavour to almost everything we eat and saves lives in winter by improving the safety of our highways.

Our plentiful supply of salt means that its value must be measured in terms of its versatility. Yet, in times past, salt was so highly prized it was used, like gold, as a medium of exchange. Our early ancestors soon learned that man, like the animals, needed salt in order to live. Ever since, not only our food, but our commerce, our politics, our religion and our superstitions have been flavoured with salt.

Primitive tribes valued salt so highly that coins were made from it. The natives of Africa's Sierra Leone were willing to sell their wives and children for salt. An oppressive salt tax was the final spark that kindled the French Revolution. Many of the world's wars have been fought for strategic salt supplies. During the American Civil War, the men and horses of General Lee's cavalry were decimated by disease because of a salt shortage that affected the future of the entire Confederacy. Salt was the reason for the construction of one of the most famous military roads in history, the Via Salaria, or Salt Road, between the salt works at Ostia and the City of Rome. The Roman legionnaires who guarded this route received a part of their pay in salt. From this ration, the "salarium argentum", derives our modern word "salary". Even today, a good employee is said to be worth his salt".

In many ancient civilizations, salt had great symbolic value. Because of its acknowledged power to purify and preserve, salt spilled on the parchment was a guarantee of good faith in signing a contract or making an agreement. Among the Greeks and the Turks, to eat salt with a stranger was a token of friendship. The Greeks made thank-offerings of salt to the gods they worshipped as givers of life. The ancient Jews offered salt to Jehovah at harvest time. In Jewish tradition today, bread and salt are the first things to be brought into a new house.

In some areas of the far East, people give their children little bags of salt to hang around their necks as protection from the "evil eye". And in parts of Russia no bride and groom would enter a new home without first throwing salt in every corner to protect them from harm and to encourage health and happiness.

Even in modern Christianity, salt has symbolic significance. The Bible contains many separate references to salt. In the ritual of baptism, salt is used as a symbol of protection against evil, representing purity of mind and soul and the power to resist temptation.

According to ancient superstition, when you spill salt, you risk losing the power to triumph over temptation and must banish evil spirits by throwing a pinch of it over your left shoulder.

The association of spilled salt and the appearance of evil is illustrated by the overturned saltcellar of the Last Supper. Judas, who has succumbed to temptation, is identified by Christ through the evil significance of the spilled salt. Which brings us back to the salt on your table. How did it get there? Where does it come from?