more at http://scitech.quickfound.net/ "Salt, its extraction and uses in national defense, industry, agriculture, and the home." Public domain film from the Library of Congress Prelinger Archive, slightly cropped to remove uneven edges, with the aspect ratio corrected, and mild video noise reduction applied. The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and equalization (the resulting sound, though far from perfect, is far less noisy than the original). http://en.wikipedia.org/wiki/Salt Salt, also known as table salt, or rock salt, is a mineral that is composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of ionic salts. It is essential for animal life in small quantities, but is harmful to animals and plants in excess. Salt is one of the oldest, most ubiquitous food seasonings and salting is an important method of food preservation. The taste of salt (saltiness) is one of the basic human tastes. Salt for human consumption is produced in different forms: unrefined salt (such as sea salt), refined salt (table salt), and iodized salt. It is a crystalline solid, white, pale pink or light gray in color, normally obtained from sea water or rock deposits. Edible rock salts may be slightly grayish in color because of mineral content. Chloride and sodium ions, the two major components of salt, are needed by all known living creatures in small quantities. Salt is involved in regulating the water content (fluid balance) of the body. The sodium ion itself is used for electrical signaling in the nervous system. Because of its importance to survival, salt has often been considered a valuable commodity during human history. However, as salt consumption has increased during modern times, scientists have become aware of the health risks associated with too much salt intake, including high blood pressure. Therefore health authorities have recommended limitations of dietary sodium. The United States Department of Health and Human Services recommends that individuals consume no more than 1500--2300 mg of sodium (3750--5750 mg of salt) per day depending on age... While people have used canning and artificial refrigeration to preserve food for the last hundred years or so, salt has been the best-known food preservative, especially for meat, for many thousands of years. A very ancient saltworks operation has been discovered at the Poiana Slatinei archaeological site next to a salt spring in Lunca, Neamţ County, Romania. Evidence indicates that Neolithic people of the Precucuteni Culture were boiling the salt-laden spring water through the process of briquetage to extract the salt as far back as 6050 BC. The salt extracted from this operation may have had a direct correlation to the rapid growth of this society's population soon after its initial production began.[ The harvest of salt from the surface of Xiechi Lake near Yuncheng in Shanxi, China dates back to at least 6000 BC, making it one of the oldest verifiable saltworks. Salt was included among funereal offerings found in ancient Egyptian tombs from the third millennium BC, as were salted birds and salt fish. From about 2800 BC, the Egyptians began exporting salt fish to the Phoenicians in return for Lebanon cedar, glass, and the dye Tyrian purple; the Phoenicians traded Egyptian salt fish and salt from North Africa throughout their Mediterranean trade empire. Along the Sahara, the Tuareg maintain routes especially for the transport of salt by Azalai (salt caravans). In 1960, the caravans still transported some 15,000 tons of salt, but this trade has now declined to roughly a third of this figure. Salzburg, Hallstatt, and Hallein lie on the river Salzach in central Austria, within a radius of no more than 17 kilometres. Salzach literally means "salt water" and Salzburg "salt city", both taking their names from the German word for salt, Salz. Hallstatt gave its name to the Celtic archaeological culture that began mining for salt in the area in around 800 BC. Around 400 BC, the Hallstatt Celts, who had heretofore mined for salt, began open pan salt making. During the first millennium BC, Celtic communities grew rich trading salt and salted meat to Ancient Greece and Ancient Rome in exchange for wine and other luxuries..

• published: 21 Dec 2011
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