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Common salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in its natural form as a crystalline mineral is known as rock salt or halite. Salt is present in vast quantities in seawater, where it is the main mineral constituent; the open ocean has about of solids per litre, a salinity of 3.5%. Salt is essential for animal life, and saltiness is one of the basic human tastes. The tissues of animals contain larger quantities of salt than do plant tissues; therefore the typical diets of nomads who subsist on their flocks and herds require little or no added salt, whereas cereal-based diets require supplementation. Salt is one of the oldest and most ubiquitous of food seasonings, and salting is an important method of food preservation. Some of the earliest evidence of salt processing dates to around 8,000 years ago, when people living in Romania were boiling spring water to extract the salts; a salt-works in China has been found which dates to approximately the same period. Salt was prized by the ancient Hebrews, the Greeks, the Romans, the Byzantines, the Hittites and the Egyptians. Salt became an important article of trade and was transported by boat across the Mediterranean Sea, along specially built salt roads, and across the Sahara in camel caravans. The scarcity and universal need for salt has led nations to go to war over salt and use it to raise tax revenues. Salt is also used in religious ceremonies and has other cultural significance. Salt is processed from salt mines, or by the evaporation of seawater (sea salt) or mineral-rich spring water in shallow pools. Its major industrial products are caustic soda and chlorine, and it is used in many industrial processes and in the manufacture of polyvinyl chloride, plastics, paper pulp and many other products. Of the annual production of around two hundred million tonnes of salt, only about 6% is used for human consumption; other uses include water conditioning processes, de-icing highways and agricultural use. Edible salt is sold in forms such as sea salt and table salt which usually contains an anti-caking agent and may be iodised to prevent iodine deficiency. As well as its use in cooking and at the table, salt is present in many processed foods. Salt is an essential nutrient and the amount of salt in the diet influences health. Too much salt can raise blood pressure and may increase the risk of heart attacks and strokes in susceptible populations.〔 The World Health Organization recommends that adults should consume less than 2,000 mg of sodium, equivalent to 5 grams of salt per day. ==History== (詳細はLatin word for salt because the Roman Legions were sometimes paid in salt, which was quite literally worth its weight in gold. In Britain, the suffix "-wich" in a placename means it was once a source of salt, as in Sandwich and Norwich. The Natron Valley was a key region that supported the Egyptian Empire to its north, because it supplied it with a kind of salt that came to be called by its name, natron. Even before this, what is now thought to have been the first city in Europe is Solnitsata, in Bulgaria, which was a salt mine, providing the area now known as the Balkans with salt since 5400 BC.〔LA Times (Bulgarians find oldest European town, a salt production center )〕 Even the name Solnisata means "salt works". 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 salt-works operation has been discovered at the Poiana Slatinei archaeological site next to a salt spring in Lunca, Neamț 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. There is more salt in animal tissues such as meat, blood and milk, than there is in plant tissues.〔 Nomads who subsist on their flocks and herds do not eat salt with their food, but agriculturalists, feeding mainly on cereals and vegetable matter, need to supplement their diet with salt. With the spread of civilization, salt became one of the world's main trading commodities. It was of high value to the ancient Hebrews, the Greeks, the Romans, the Byzantines, the Hittites and other peoples of antiquity. In the Middle East, salt was used to ceremonially seal an agreement, and the ancient Hebrews made a "covenant of salt" with God and sprinkled salt on their offerings to show their trust in Him. An ancient practice in time of war was salting the earth: scattering salt around in a defeated city in order to prevent plant growth. Abimelech was ordered by God to do this at Shechem, and various texts claim that the Roman general Scipio Aemilianus Africanus ploughed over and sowed the city of Carthage with salt after it was defeated in the Third Punic War (146 BC). Salt may have been used for barter in connection with the obsidian trade in Anatolia in the Neolithic Era. Herodotus described salt trading routes across Libya back in the 5th century BC. In the early years of the Roman Empire, roads such as the Via Salaria were built for the transportation of salt from the salt pans of Ostia to the capital. Salt was included among funeral 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. In Africa, salt was used as currency south of the Sahara, and slabs of rock salt were used as coins in Abyssinia.〔 Moorish merchants in the 6th century traded salt for gold, weight for weight. The Tuareg have traditionally maintained routes across the Sahara especially for the transportation of salt by Azalai (salt caravans). The caravans still cross the desert from southern Niger to Bilma, although much of the trade now takes place by truck. Each camel takes two bales of fodder and two of trade goods northwards and returns laden with salt pillars and dates. Salzburg, Hallstatt, and Hallein lie within of each other on the river Salzach in central Austria in an area with extensive salt deposits. Salzach literally means "salt river" and Salzburg "salt castle", both taking their names from the German word ドイツ語:''Salz'' meaning salt and Hallstatt was the site of the world's first salt mine. The town gave its name to the Hallstatt culture that began mining for salt in the area in about 800 BC. Around 400 BC, the townsfolk, who had previously used pickaxes and shovels, 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. The word ''salary'' originates from (ラテン語:salarium) which referred to the money paid to the Roman Army's soldiers for the purchase of salt.〔See, for example, the following dictionary entries: * * * (【引用サイトリンク】publisher=Answers.com )〕 The word ''salad'' literally means "salted", and comes from the ancient Roman practice of salting leaf vegetables. Wars have been fought over salt. Venice fought and won a war with Genoa over the product, and it played an important part in the American Revolution. Cities on overland trade routes grew rich by levying duties,〔 and towns like Liverpool flourished on the export of salt extracted from the salt mines of Cheshire. Various governments have at different times imposed salt taxes on their peoples. The voyages of Christopher Columbus are said to have been financed from salt production in southern Spain, and the oppressive salt tax in France was one of the causes of the French Revolution. After being repealed, this tax was reimposed by Napoleon when he became emperor to pay for his foreign wars, and was not finally abolished until 1945. In 1930, Mahatma Gandhi led at least 100,000 people on the "Dandi March" or "Salt Satyagraha", in which protesters made their own salt from the sea thus defying British rule and avoiding paying the salt tax. This civil disobedience inspired millions of common people, and elevated the Indian independence movement from an elitist movement to a national struggle. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「salt」の詳細全文を読む スポンサード リンク
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