Monday, February 4, 2008


Salt is a dietary mineral essential for animal life, composed primarily of sodium chloride. Salt for human consumption is produced in different forms: unrefined salt (such as sea salt), refined salt (table salt), and iodised salt. It is a crystalline solid, white, pale pink or light grey in color, normally obtained from sea water or rock deposits. Edible rock salts may be slightly greyish in color due to this mineral content.

Chloride and sodium ions, the two major components of salt, are necessary for the survival of all living creatures including humans. Some isolated cultures, such as the Yanomami in South America, have been found to consume little salt, possibly an adaptation originated in the predominantly vegetarian diet of human primate ancestors. Salt is involved in regulating the water content (fluid balance) of the body. Salt flavor is one of the basic tastes. Salt cravings may be caused by trace mineral deficiencies as well as by a deficiency of sodium chloride itself.

It is believed that over consumption of salt may increase the risk of health problems, including high blood pressure. In food preparation, salt is used as a preservative and as a seasoning.

Common salt (NaCl) has been used for dietary purposes as well as a preservative, a medium of exchange and a source of tax revenue since the ancient times.

During the times of the historian Herodotus, salt was known along the Libyan desert. Pliny the elder remarked "Heaven known, a civilised life is impossible without salt." Pliny lists India, Arabia and Africa as sources for extraction of salt.

Salt was one of the main marine resources of the Harappans, who may have used a site near the Gulf of Khambat for salt extraction. Methods of both the salt mining and the procurement by sea were known in ancient India. Salt mines from ancient India were the center of widespread trade. Roman soldiers received some of their salaries in form of salt, with the arrangement then known as salarium. The ancient Mayan civilization also produced salt. The method of boiling of brine to recover salt was known in Iron Age Europe.

Japan developed a two step process for concentration and evaporation which has existed since at least 600 CE. The middle ages saw East Africa develop methods to extract salt from the brine deposits originating in the rift systems Elaborate arrangements were made to ensure salt productions, including ditches, storage tanks and the use of various heating techniques.

There are thirty-five verses which reference salt in the English translation of the Bible (King James Version), the earliest being the story of Lot's wife, who was turned into a pillar of salt when she disobediently looked back at the wicked cities of Sodom (Genesis 19:26). When King Abimelech destroyed the city of Shechem he is said to have "sowed salt on it;" a phrase expressing the completeness of its ruin. (Judges 9:45.) In the Sermon on the Mount, Jesus referred to his followers as the "salt of the earth". The apostle Paul also encouraged Christians to "let your conversation be always full of grace, seasoned with salt" (Colossians 4:6) so that when others enquire about their beliefs, the Christian's answer generates a 'thirst' to know more about Christ.

Salt is mandatory in the rite of the Tridentine Mass. Salt is used in the third item (which includes an Exorcism) of the Celtic Consecration (refer Gallican rite) that is employed in the consecration of a church. Salt may be added to the water "where it is customary" in the Roman Catholic rite of Holy water.

In the native Japanese religion Shinto, salt is used for ritual purification of locations and people, such as in Sumo Wrestling.

In Aztec mythology, Huixtocihuatl was a fertility goddess who presided over salt and salt water.

Different natural salts have different mineralities, giving each one a unique flavor. Fleur de sel, natural sea salt harvested by hand, has a unique flavor varying from region to region.

Some advocates for sea salt assert that unrefined sea salt is more healthy than refined salts. However, completely raw sea salt is bitter due to magnesium and calcium compounds, and thus is rarely eaten. The refined salt industry cites scientific studies saying that raw sea and rock salts do not contain enough iodine salts to prevent iodine deficiency diseases.

Refined salt, which is most widely used presently, is mainly sodium chloride. Food grade salt accounts for only a small part of salt production in industrialised countries (3% in Europe) although world-wide, food uses account for 17.5% of salt production. The majority is sold for industrial use. Salt has great commercial value, because it is a necessary ingredient in the manufacturing of many things. A few common examples include: the production of pulp and paper, setting dyes in textiles and fabrics, and the making of soaps and detergents.

The manufacture and use of salt is one of the oldest chemical industries. Salt is also obtained by evaporation of sea water, usually in shallow basins warmed by sunlight; salt so obtained was formerly called bay salt, and is now often called sea salt or solar salt. Today, most refined salt is prepared from rock salt: mineral deposits high in 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.

After the raw salt is obtained, it is refined to purify it and improve its storage and handling characteristics. Purification usually involves recrystallization. In recrystallization, a brine solution is treated with chemicals that precipitate most impurities (largely magnesium and calcium salts). Multiple stages of evaporation are then used to collect pure sodium chloride crystals, which are kiln-dried.

Since the 1950s it has been common to add a trace of sodium hexacyanoferrate(II) to the brine; this acts as an anticaking agent by promoting irregular crystals. Other anticaking agents (and potassium iodide, for iodised salt) are generally added after crystallization.[citation needed] These agents are hygroscopic chemicals which absorb humidity, keeping the salt crystals from sticking together. Some anticaking agents used are tricalcium phosphate, calcium or magnesium carbonates, fatty acid salts (acid salts), magnesium oxide, silicon dioxide, calcium silicate, sodium alumino-silicate, and alumino-calcium silicate. Concerns have been raised regarding the possible toxic effects of aluminium in the latter two compounds[citation needed]; however, both the European Union and the United States Food and Drug Administration (FDA) permit their use. The refined salt is then ready for packing and distribution.

Iodized salt (BrE: iodised salt) is table salt mixed with a minute amount of potassium iodide, sodium iodide, or iodate. Iodized salt is used to help reduce the chance of iodine deficiency in humans. Iodine deficiency commonly leads to thyroid gland problems, specifically endemic goiter. Endemic goiter is a disease characterized by a swelling of the thyroid gland, usually resulting in a bulbous protrusion on the neck. While only tiny quantities of iodine are required in a diet to prevent goiter, the United States Food and Drug Administration recommends 150 micrograms of iodine per day for both men and women, and there are many places around the world where natural levels of iodine in the soil are low and the iodine is not taken up by vegetables.

Today, iodized salt is more common in the United States, Australia and New Zealand than in the United Kingdom. Table salt is also often iodized—a small amount of potassium iodide (in the US) or potassium iodate (in the EU) is added as an important dietary supplement. Table salt is mainly employed in cooking and as a table condiment. 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 goitre, cretinism in children, and myxedema in adults.

The amount of iodine and the specific iodine compound added to salt varies from country to country. In the United States, iodized salt contains 46-77 ppm, while in the UK the iodine content of iodized salt is recommended to be 10-22 ppm.

In some European countries where drinking water fluoridation is not practiced, fluorinated table salt is available. In France, 35% of sold table salt contains either sodium fluoride or potassium fluoride. Another additive, especially important for pregnant women, is Folic acid (Vitamin B9), which gives the table salt a yellow color.

In Canada, at least one brand (Windsor salt) contains invert sugar. The reason for this is unclear.

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