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Salt is a
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure, that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

mineral
composed primarily of
sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g/m ...

sodium chloride
(NaCl), a
chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) composed of atoms from more than one element held together by chemical bonds. A molecule consisting of atoms of only one element is therefor ...

chemical compound
belonging to the larger class of
salts In chemistry, a salt is a chemical compound consisting of an ionic assembly of cations and anions. Salts are composed of related numbers of cations (positively charged ions) and anions (negatively charged ions) so that the product is electrically ...

salts
; salt in its natural form as a
crystalline A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macrosco ...

crystalline
mineral is known as rock salt or
halite Halite ( or ), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride (Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, p ...

halite
. Salt is present in vast quantities in
seawater Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/l, 35 ppt, 599 mM). This means that every kilogram (roughly one liter by volume) of seawater has approxim ...

seawater
, where it is the main mineral constituent. The open ocean has about of solids per liter of sea water, a
salinity upInternational Association for the Physical Sciences of the Oceans (IAPSO) standard seawater. Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). This is usually measured in \ ...

salinity
of 3.5%.
Salt is essential for life in general
Salt is essential for life in general
, and
saltiness The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste (flavor). Taste is the perception produced or stimulated when a substance in the mouth reacts chemically with taste receptor ce ...

saltiness
is one of the
basic human tastes
basic human tastes
. Salt is one of the oldest and most ubiquitous food
seasoning Seasoning is the process of adding herbs or spices to food to enhance the flavour. General meaning Seasonings include herbs and spices, which are themselves frequently referred to as "seasonings". However, ''Larousse Gastronomique'' states that '' ...

seasoning
s, and
salting
salting
is an important method of
food preservation Food preservation includes food processing practices which prevent the growth of microorganisms, such as yeasts (although some methods work by introducing benign bacteria or fungi to the food), and slow the oxidation of fats that cause rancidity. ...

food preservation
. Some of the earliest evidence of salt processing dates to around 6,000 BC, when people living in the area of present-day Romania boiled
spring water in Missouri at a rate of . A spring is a point at which water flows from an aquifer to the Earth's surface. It is a component of the hydrosphere. Formation in Michigan A spring may be the result of karst topography where surface water has i ...

spring water
to extract salts; a
salt-works in China
salt-works in China
dates to approximately the same period. Salt was also prized by the ancient
Hebrews The terms ''Hebrews'' ( / , Modern: ' / ', Tiberian: ' / '; ISO 259-3: ' / ') and ''Hebrew people'' are mostly taken as synonymous with the Semitic-speaking Israelites, especially in the pre-monarchic period when they were still nomadic. Howev ...

Hebrews
, the
Greeks The Greeks or Hellenes (; el|Έλληνες, ''Éllines'' ) are an ethnic group native to Greece, Cyprus, Albania, Italy, Turkey, Egypt and, to a lesser extent, other countries surrounding the Mediterranean Sea. They also form a significant di ...

Greeks
, the
Romans Roman or Romans usually refers to: *Rome, the capital city of Italy *Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of ancient Rome *''Epistle to the Romans'', shortened to ''Romans'', a letter in ...

Romans
, the
Byzantines
Byzantines
, the
Hittites The Hittites () were an Anatolian people who played an important role in establishing an empire centered on Hattusa in north-central Anatolia around 1680–1650 BCE. This empire reached its height during the mid-14th century BC under Šuppiluli ...

Hittites
,
Egyptians Egyptians are the people originating from the country of Egypt. Egyptian identity is closely tied to geography. The population is concentrated in the lower Nile Valley, a small strip of cultivable land stretching from the First Cataract to the Me ...

Egyptians
, and the
Indians
Indians
. 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 on camel caravans. The scarcity and universal need for salt have led nations to go to war over it and use it to raise tax revenues. Salt is used in religious ceremonies and has other cultural and traditional significance. Salt is processed from
salt mines A salt mine is a mine from which salt is extracted. The mined salt is usually in the form of halite (commonly known as rock salt), and extracted from evaporite formations. History Before the advent of the modern internal combustion engine and ...

salt mines
, and by the
evaporation 280px|Demonstration of evaporative cooling. When the sensor is dipped in ethanol and then taken out to evaporate, the instrument shows progressively lower temperature as the ethanol evaporates. Evaporation is a type of vaporization that occurs ...

evaporation
of seawater (
sea salt Sea salt is salt that is produced by the evaporation of seawater. It is used as a seasoning in foods, cooking, cosmetics and for preserving food. It is also called bay salt, solar salt, or simply salt. Like mined rock salt, production of sea salt ...

sea salt
) and mineral-rich spring water in shallow pools. Its major industrial products are
caustic soda#REDIRECT Sodium hydroxide#REDIRECT Sodium hydroxide#REDIRECT Sodium hydroxide {{Redirect category shell|1= {{R from other capitalisation ... {{Redirect category shell|1= {{R from other capitalisation ...
{{Redirect category shell|1= {{R f ...

caustic soda
and
chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is a y ...

chlorine
; salt is used in many industrial processes including the manufacture of
polyvinyl chloride Polyvinyl chloride (colloquial: polyvinyl, vinyl; abbreviated: PVC) is the world's third-most widely produced synthetic plastic polymer (after polyethylene and polypropylene). About 40 million tons of PVC are produced each year. PVC comes in ...

polyvinyl chloride
,
plastic Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptability, ...

plastic
s,
paper pulp Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibers from wood, fiber crops, waste paper, or rags. Mixed with water and other chemical or plant-based additives, pulp is the major raw material ...

paper pulp
and many other products. Of the annual global production of around two hundred million
tonne The tonne ( or ; symbol: t) is a metric unit of mass equal to 1,000 kilograms. It is commonly referred to as a metric ton in the United States. It is equivalent to approximately pounds, or approximately 0.984 long tons (UK). The offi ...

tonne
s of salt, about 6% is used for human consumption. Other uses include water conditioning processes,
de-icing De-icing is the process of removing snow, ice or frost from a surface. Anti-icing is understood to be the application of chemicals that not only de-ice but also remain on a surface and continue to delay the reformation of ice for a certain period ...

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 agentAn anticaking agent is an additive placed in powdered or granulated materials, such as table salt or confectioneries, to prevent the formation of lumps (caking) and for easing packaging, transport, flowability, and consumption. Caking mechanisms dep ...

anti-caking agent
and may be
iodised
iodised
to prevent
iodine deficiency Iodine deficiency is a lack of the trace element iodine, an essential nutrient in the diet. It may result in metabolic problems such as goiter, sometimes as an endemic goiter as well as congenital iodine deficiency syndrome due to untreated congen ...

iodine deficiency
. As well as its use in cooking and at the table, salt is present in many processed foods. Sodium is an
essential nutrient A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excreted ...

essential nutrient
for human health via its role as an
electrolyte An electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent, such as water. The dissolved electrolyte separates into cations and anions, which disperse uniformly through the solvent. Electricall ...

electrolyte
and
osmotic solute
osmotic solute
. Excessive salt consumption may increase the risk of
cardiovascular diseases Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, heart ...

cardiovascular diseases
, such as
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure typically does not cause symptoms. Long-term high blo ...

hypertension
, in children and adults. Such
health effects of salt Health is a state of physical, mental and social well-being in which disease and infirmity are absent.World Health Organization. (2006)''Constitution of the World Health Organization''– ''Basic Documents'', Forty-fifth edition, Supplement, Octo ...

health effects of salt
have long been studied. Accordingly, numerous world health associations and experts in developed countries recommend reducing consumption of popular salty foods. The
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution, which establishes the agency's governing structure and principles, states its main objective as ...

World Health Organization
recommends that adults should consume less than 2,000 mg of sodium, equivalent to 5 grams of salt per day.


History

All through history, the availability of salt has been pivotal to civilization. What is now thought to have been the first city in Europe is
Solnitsata Solnitsata ( bg|Солницата, "The Saltworks") was an ancient town located in present-day Bulgaria, near the modern city of Provadia. Believed by Bulgarian archaeologists to be the oldest town in Europe, Solnitsata was the site of a salt prod ...

Solnitsata
, in
Bulgaria Bulgaria (; bg|България|Bǎlgariya), officially the Republic of Bulgaria ( bg|Република България|links=no|Republika Bǎlgariya, ), is a country in Southeast Europe. It is bordered by Romania to the north, Serbia and No ...

Bulgaria
, which was a salt mine, providing the area now known as the
Balkans The Balkans ( ), also known as the Balkan Peninsula, are a geographic area in southeastern Europe with various definitions and meanings, including geopolitical and historical. The region takes its name from the Balkan Mountains that stretch t ...

Balkans
with salt since 5400 BC. Even the name Solnitsata means "salt works". While people have used
canning Special-edition steel soup cans commemorating paintings ">Campbell's Soup Cans#altered colors">paintings Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container (jars like Mason ...

canning
and artificial
refrigeration The term refrigeration means cooling a space, substance or system to lower and/or maintain its temperature below the ambient one (while the removed heat is rejected at a higher temperature).International Dictionary of Refrigeration, http://diction ...

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 ,
Neamț County Neamț County () is a county (județ) of Romania, in the historic region of Moldavia, with the county seat at Piatra Neamț. The county takes its name from the Neamț River. Demographics In 2011, it had a population of 470,766 and a population de ...

Neamț County
, Romania. Evidence indicates that [[Neolithic people of the [[Cucuteni-Trypillian culture|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, Shanxi|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 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 to prevent plant growth. The [[Bible tells the story of King [[Abimelech who was ordered by God to do this at [[Shechem, and various texts claim that the [[Roman Republic|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|Neolithic Era. 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 salted fish and salt from [[North Africa throughout their Mediterranean trade empire. [[Herodotus described salt trading routes across Libya back in the 5th century BC. In the early years of the Roman Empire, roads were built for the transportation of salt from the salt imported at [[Ostia (Rome)|Ostia to the capital. In Africa, salt was used as currency south of the Sahara, and slabs of rock salt were used as coins in [[Ethiopia|Abyssinia. Moorish merchants in the 6th century traded salt for gold, weight for weight. The [[Tuareg people|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. In Gabon, before the arrival of Europeans, the coast people carried on a remunerative trade with those of the interior by the medium of sea salt. This was gradually displaced by the salt that Europeans brought in sacks, so that the coast natives lost their previous profits; as of the author's writing in 1958, sea salt was still the currency best appreciated in the interior. [[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 language|German word meaning salt and Hallstatt was the site of the world's first [[Salt mining|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 [[Salt-cured meat|salted meat to [[Ancient Greece and [[Ancient Rome in exchange for wine and other luxuries. The word ''[[salary'' comes from the [[Latin word for salt. The reason for this is unknown; a persistent modern claim that the [[Roman Legions were sometimes paid in salt is baseless. The word ''salad'' literally means "salted", and comes from the ancient Roman practice of salting [[leaf vegetables. Wars have been fought over salt. [[Republic of Venice|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 [[Duty (economics)|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 [[Gabelle|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 [[Napoleonic Wars|foreign wars, and was not finally abolished until 1946. In 1930, [[Mahatma Gandhi led a crowd of 100,000 protestors on the "Dandi March" or "[[Salt Satyagraha", during which they made their own salt from the sea as a demonstration of their opposition to the [[History of the British salt tax in India|colonial salt tax. This act of [[civil disobedience inspired numerous Indians and transformed the [[Indian independence movement from an elitist one with little popular support into a national struggle.


Chemistry

Salt is mostly
sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g/m ...

sodium chloride
, the [[ionic compound with the [[chemical formula|formula NaCl, representing equal proportions of [[sodium and
chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is a y ...

chlorine
. [[Sea salt and freshly mined salt (much of which is sea salt from prehistoric seas) also contain small amounts of [[trace elements (which in these small amounts are generally good for plant and animal health ). Mined salt is often refined in the production of table salt; it is dissolved in water, purified via [[precipitation (chemistry)|precipitation of other minerals out of solution, and re-evaporated. During this same refining process it is often also [[iodised salt|iodized. Salt crystals are translucent and cubic in shape; they normally appear white but impurities may give them a blue or purple tinge. The [[molar mass of salt is 58.443 g/mol, its melting point is 801 °C (1,474 °F) and its boiling point 1,465 °C (2,669 °F). Its density is 2.17 grams per cubic centimetre and it is readily soluble in water. When dissolved in water it separates into Na+ and Cl ions, and the solubility is 359 grams per litre. From cold solutions, salt crystallises as the [[water of hydration|dihydrate NaCl·2H2O. Solutions of sodium chloride have very different properties from those of pure water; the [[freezing point is −21.12 °C (−6.02 °F) for 23.31 wt% of salt, and the [[boiling point of saturated salt solution is around 108.7 °C (227.7 °F).Elvers, B. ''et al.'' (ed.) (1991) ''Ullmann's Encyclopedia of Industrial Chemistry'', 5th ed. Vol. A24, Wiley, p. 319,


Edible salt

Salt is essential to the health of humans and other animals, and it is one of the [[Basic tastes#Basic tastes|five basic taste sensations. Salt is used in many cuisines around the world, and it is often found in [[salt shakers on diners' eating tables for their personal use on food. Salt is also an ingredient in many manufactured foodstuffs. Table salt is a refined salt containing about 97 to 99 percent
sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g/m ...

sodium chloride
. Usually, [[anticaking agents such as [[sodium aluminosilicate or [[magnesium carbonate are added to make it free-flowing. [[Iodized salt, containing [[potassium iodide, is widely available. Some people put a [[desiccant, such as a few grains of uncooked [[rice or a [[saltine cracker, in their salt shakers to absorb extra moisture and help break up salt clumps that may otherwise form.


Fortified table salt

Some table salt sold for consumption contains additives which address a variety of health concerns, especially in the developing world. The identities and amounts of additives vary widely from country to country. [[Iodine is an important micronutrient for humans, and a [[iodine deficiency|deficiency of the element can cause lowered production of [[thyroxine ([[hypothyroidism) and enlargement of the thyroid gland ([[endemic goitre) in adults or [[cretinism in children. Iodized salt has been used to correct these conditions since 1924 and consists of table salt mixed with a minute amount of [[potassium iodide, [[sodium iodide or [[sodium iodate. A small amount of [[dextrose may also be added to stabilize the iodine. Iodine deficiency affects about two billion people around the world and is the leading preventable cause of [[mental retardation. Iodized table salt has significantly reduced disorders of iodine deficiency in countries where it is used. The amount of iodine and the specific iodine compound added to salt varies from country to country. In the [[United States, the [[Food and Drug Administration (FDA) recommends 150 [[micrograms of iodine per day for both men and women. US iodized salt contains 46–77 ppm (parts per million), whereas in the UK the iodine content of iodized salt is recommended to be 10–22 ppm. [[Sodium ferrocyanide, also known as yellow [[prussiate of soda, is sometimes added to salt as an [[anticaking agent. The additive is considered safe for human consumption. Such anticaking agents have been added since at least 1911 when [[magnesium carbonate was first added to salt to make it flow more freely. The safety of sodium ferrocyanide as a food additive was found to be provisionally acceptable by the [[Committee on Toxicity in 1988.Discussions of the safety of sodium hexaferrocyanate in table salt
. Hansard.millbanksystems.com (5 May 1993). Retrieved 7 July 2011.
Other anticaking agents sometimes used include [[tricalcium phosphate, [[calcium carbonate|calcium or magnesium carbonates, [[fatty acid salts ([[acid salts), [[magnesium oxide, [[silicon dioxide, [[calcium silicate, sodium aluminosilicate and [[calcium aluminosilicate. Both the European Union and the United States Food and Drug Administration permitted the use of [[aluminium in the latter two compounds. In "doubly fortified salt", both iodide and iron salts are added. The latter alleviates [[iron deficiency anaemia, which interferes with the mental development of an estimated 40% of infants in the developing world. A typical iron source is [[Iron(II) fumarate|ferrous fumarate. Another additive, especially important for [[pregnancy|pregnant women, is [[folic acid (vitamin B9), which gives the table salt a yellow color. Folic acid helps prevent [[neural tube defects and anaemia, which affect young mothers, especially in developing countries. A lack of [[fluorine in the diet is the cause of a greatly increased incidence of [[dental caries. [[Fluoride salts can be added to table salt with the goal of reducing tooth decay, especially in countries that have not benefited from fluoridated toothpastes and fluoridated water. The practice is more common in some European countries where [[water fluoridation is not carried out. In [[France, 35% of the table salt sold contains added [[sodium fluoride.


Other kinds

Unrefined
sea salt Sea salt is salt that is produced by the evaporation of seawater. It is used as a seasoning in foods, cooking, cosmetics and for preserving food. It is also called bay salt, solar salt, or simply salt. Like mined rock salt, production of sea salt ...

sea salt
contains small amounts of [[magnesium and [[calcium [[halides and [[sulfates, traces of [[algae|algal products, salt-resistant bacteria and sediment particles. The calcium and magnesium salts confer a faintly bitter overtone, and they make unrefined sea salt [[hygroscopic (i.e., it gradually absorbs moisture from air if stored uncovered). Algal products contribute a mildly "fishy" or "sea-air" odour, the latter from [[Organobromine compound#Organobromine compounds in nature|organobromine compounds. Sediments, the proportion of which varies with the source, give the salt a dull grey appearance. Since taste and aroma compounds are often detectable by humans in minute concentrations, sea salt may have a more complex flavor than pure sodium chloride when sprinkled on top of food. When salt is added during cooking however, these flavors would likely be overwhelmed by those of the food ingredients. The refined salt industry cites scientific studies saying that raw sea and rock salts do not contain enough [[iodine salts to prevent [[Iodine deficiency|iodine deficiency diseases. [[File:CH-NB - Afghanistan, Bamiyan, Bamyan (Bamian)- Menschen - Annemarie Schwarzenbach - SLA-Schwarzenbach-A-5-20-159.jpg|Two men with stacks of rock salt in [[Bamyan Province|Bamyan, [[Afghanistan Different natural salts have different [[Minerality#I–P|mineralities depending on their source, giving each one a unique flavour. [[Fleur de sel, a natural sea salt from the surface of evaporating brine in salt pans, has a unique flavour varying with the region from which it is produced. In traditional [[Korean cuisine, so-called "[[jugyeom|bamboo salt" is prepared by roasting salt in a [[bamboo container plugged with mud at both ends. This product absorbs minerals from the bamboo and the mud, and has been claimed to increase the [[clastogen|anticlastogenic and [[mutagen|antimutagenic properties of [[doenjang (a fermented bean paste). [[Kosher salt|Kosher or kitchen salt has a larger grain size than table salt and is used in cooking. It can be useful for [[brining, bread or [[pretzel making and as a scrubbing agent when combined with oil. [[Pickling salt is made of ultra-fine grains to speed dissolving to make [[brine.


Salt in food

Salt is present in most [[foods, but in naturally occurring foodstuffs such as meats, vegetables and fruit, it is present in very small quantities. It is often added to processed foods (such as [[canning|canned foods and especially [[salting (food)|salted foods, [[pickling|pickled foods, and [[snack foods or other [[convenience foods), where it functions as both a [[preservative and a [[flavoring. [[Dairy salt is used in the preparation of butter and cheese products. As a flavoring, salt enhances the taste of other foods by suppressing the bitterness of those foods making them more palatable and relatively sweeter. Before the advent of electrically powered
refrigeration The term refrigeration means cooling a space, substance or system to lower and/or maintain its temperature below the ambient one (while the removed heat is rejected at a higher temperature).International Dictionary of Refrigeration, http://diction ...

refrigeration
, salting was one of the main methods of
food preservation Food preservation includes food processing practices which prevent the growth of microorganisms, such as yeasts (although some methods work by introducing benign bacteria or fungi to the food), and slow the oxidation of fats that cause rancidity. ...

food preservation
. Thus, [[herring contains 67 mg sodium per 100 g, while [[kipper, its preserved form, contains 990 mg. Similarly, [[pork typically contains 63 mg while [[bacon contains 1,480 mg, and [[potatoes contain 7 mg but [[potato crisps 800 mg per 100 g. Salt is also used in [[cooking, such as with [[salt crusts. The main sources of salt in the Western diet, apart from direct use of sodium chloride, are bread and cereal products, meat products and milk and dairy products. In many East Asian cultures, salt is not traditionally used as a condiment. In its place, condiments such as [[soy sauce, [[fish sauce and [[oyster sauce tend to have a high sodium content and fill a similar role to table salt in western cultures. They are most often used for cooking rather than as table condiments.


Biology of salt taste

Human salt [[taste is detected by sodium [[Taste receptor|taste receptors present in taste bud cells on the tongue. Human sensory taste testing studies have shown that [[Proteolysis|proteolyzed forms of [[epithelial sodium channel (ENaC) function as the human salt taste receptor.


Sodium consumption and health

Table salt is made up of just under 40% sodium by weight, so a 6g serving (1teaspoon) contains about 2,400mg of sodium. Sodium serves a vital purpose in the human body: via its role as an electrolyte, it helps nerves and muscles to function correctly, and it is one factor involved in the [[autoregulation|osmotic regulation of water content in body organs ([[fluid balance). Most of the sodium in the [[Western diet comes from salt. The habitual salt intake in many Western countries is about 10 g per day, and it is higher than that in many countries in Eastern Europe and Asia. The high level of sodium in many processed foods has a major impact on the total amount consumed. In the United States, 75% of the sodium eaten comes from processed and restaurant foods, 11% from cooking and table use and the rest from what is found naturally in foodstuffs. Because consuming too much sodium increases risk of [[cardiovascular diseases, health organizations generally recommend that people reduce their dietary intake of salt. High sodium intake is associated with a greater risk of [[stroke, total cardiovascular disease and [[kidney disease. A reduction in sodium intake by 1,000 mg per day may reduce cardiovascular disease by about 30 percent. In adults and children with no acute illness, a decrease in the intake of sodium from the typical high levels reduces blood pressure. A low sodium diet results in a greater improvement in blood pressure in people with
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure typically does not cause symptoms. Long-term high blo ...

hypertension
. The
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution, which establishes the agency's governing structure and principles, states its main objective as ...

World Health Organization
recommends that adults should consume less than 2,000 mg of sodium (which is contained in 5g of salt) per day. Guidelines by the United States recommend that people with hypertension, African Americans, and middle-aged and older adults should limit consumption to no more than 1,500 mg of sodium per day and meet the potassium recommendation of 4,700 mg/day with a healthy diet of fruits and vegetables. While reduction of sodium intake to less than 2,300 mg per day is recommended by developed countries, one review recommended that sodium intake be reduced to at least 1,200 mg (contained in 3g of salt) per day, as a further reduction in salt intake the greater the fall in systolic blood pressure for all age groups and ethinicities. Another review indicated that there is inconsistent/insufficient evidence to conclude that reducing sodium intake to lower than 2,300 mg per day is either beneficial or harmful. More recent evidence is showing a much more complicated relationship between salt and cardiovascular disease. According to a systematic review of multiple large studies, "mortality caused by levels of salt the association between sodium consumption and cardiovascular disease or mortality is U-shaped, with increased risk at both high and low sodium intake." The findings showed that increased mortality from excessive salt intake was primarily associated with individuals with hypertension. The levels of increased mortality among those with restricted salt intake appeared to be similar regardless of blood pressure. This evidence shows that while those with hypertension should primarily focus on reducing sodium to recommended levels, all groups should seek to maintain a healthy level of sodium intake of between 4 and 5 grams a day. One of the two most prominent dietary risks for disability in the world is eating too much sodium.


Non-dietary uses

Only about 6% of the salt manufactured in the world is used in food. Of the remainder, 12% is used in water conditioning processes, 8% goes for de-icing highways and 6% is used in agriculture. The rest (68%) is used for manufacturing and other industrial processes, and sodium chloride is one of the largest inorganic raw materials used by volume. Its major chemical products are
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caustic soda and
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chlorine
, which are separated by the [[electrolysis of a pure brine solution. These are used in the manufacture of [[PVC,
plastic Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptability, ...

plastic
s,
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paper pulp
and many other inorganic and organic compounds. Salt is also used as a [[Flux (metallurgy)|flux in the production of [[aluminium. For this purpose, a layer of melted salt floats on top of the molten metal and removes iron and other metal contaminants. It is also used in the manufacture of [[soaps and [[glycerine, where it is added to the vat to precipitate out the [[Saponification|saponified products. As an emulsifier, salt is used in the manufacture of [[synthetic rubber, and another use is in the firing of [[pottery, when salt added to the furnace vaporises before condensing onto the surface of the ceramic material, forming a strong [[Ceramic glaze|glaze. When drilling through loose materials such as sand or gravel, salt may be added to the [[drilling fluid to provide a stable "wall" to prevent the hole collapsing. There are many other processes in which salt is involved. These include its use as a [[mordant in [[textile dying, to regenerate [[resins in water softening, for the [[Tanning (leather)|tanning of hides, the preservation of meat and fish and the
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canning
of meat and vegetables.


Production

Food-grade salt accounts for only a small part of salt production in [[Developed country|industrialized countries (7% in Europe), although worldwide, food uses account for 17.5% of total production. In 2018, total world production of salt was 300 million
tonne The tonne ( or ; symbol: t) is a metric unit of mass equal to 1,000 kilograms. It is commonly referred to as a metric ton in the United States. It is equivalent to approximately pounds, or approximately 0.984 long tons (UK). The offi ...

tonne
s, the top six producers being China (68 million), the United States (42 million), India (29 million), Germany (13 million), Canada (13 million) and Australia (12 million). The manufacture of salt is one of the oldest chemical industries. A major source of salt is seawater, which has a
salinity upInternational Association for the Physical Sciences of the Oceans (IAPSO) standard seawater. Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). This is usually measured in \ ...

salinity
of approximately 3.5%. This means that there are about of [[sea salt|dissolved salts, predominantly [[sodium () and [[chloride () [[ions, per kilogram (2.2 lbs) of water. The world's oceans are a virtually inexhaustible source of salt, and this abundance of supply means that reserves have not been calculated. The evaporation of seawater is the production method of choice in marine countries with high evaporation and low precipitation rates. [[Salt evaporation ponds are filled from the ocean and salt crystals can be harvested as the water dries up. Sometimes these ponds have vivid colours, as some species of algae and other micro-organisms thrive in conditions of high salinity. Elsewhere, salt is extracted from the vast sedimentary deposits which have been laid down over the millennia from the evaporation of seas and lakes. These are either [[salt mine|mined directly, producing rock salt, or are extracted in solution by pumping water into the deposit. In either case, the salt may be purified by mechanical evaporation of brine. Traditionally, this was done in [[Open pan salt making|shallow open pans which were heated to increase the rate of evaporation. More recently, the process is performed in pans under [[vacuum. The raw salt is refined to purify it and improve its storage and handling characteristics. This usually involves recrystallization during which 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. Some salt is produced using the [[Alberger process, which involves vacuum pan evaporation combined with the seeding of the solution with cubic crystals, and produces a grainy-type flake. The [[Ayoreo people|Ayoreo, an indigenous group from the Paraguayan [[Gran Chaco people|Chaco, obtain their salt from the ash produced by burning the timber of the Indian salt tree (''Maytenus vitis-idaea'') and other trees. One of the largest [[salt mining operations in the world is at the [[Khewra Salt Mine in Pakistan. The mine has nineteen storeys, eleven of which are underground, and of passages. The salt is dug out by the [[room and pillar method, where about half the material is left in place to support the upper levels. Extraction of [[Himalayan salt is expected to last 350 years at the present rate of extraction of around 385,000 tons per annum.


In religion

Salt has long held an important place in religion and culture. At the time of [[Historical Vedic religion|Brahmanic sacrifices, in [[Hittites|Hittite rituals and during festivals held by [[Semitic people|Semites and Greeks at the time of the [[new moon, salt was thrown into a fire where it produced crackling noises. The ancient Egyptians, Greeks and Romans invoked their gods with offerings of salt and water and some people think this to be the origin of [[Holy Water in the Christian faith. In [[Aztec mythology, [[Huixtocihuatl was a fertility goddess who presided over salt and salt water. Salt is considered to be a very auspicious substance in [[Hinduism and is used in particular religious ceremonies like house-warmings and weddings. In [[Jainism, devotees lay an offering of raw rice with a pinch of salt before a deity to signify their devotion and salt is sprinkled on a person's cremated remains before the ashes are buried. Salt is believed to ward off evil spirits in [[Mahayana Buddhism|Mahayana Buddhist tradition, and when returning home from a [[funeral, a pinch of salt is thrown over the left shoulder as this prevents evil spirits from entering the house. In [[Shinto, is used for [[ritual purification of locations and people ([[harae, specifically shubatsu), and small piles of salt are placed in dishes by the entrance of establishments for the twofold purposes of warding off evil and attracting patrons. In the [[Hebrew Bible, there are thirty-five verses which [[Salt in the Bible|mention salt. One of these mentions [[Lot's wife, who was turned into a pillar of salt when she looked back at the cities of [[Sodom and Gomorrah ([[Book of Genesis|Genesis 19:26) as they were destroyed. When the judge [[Abimelech (Judges)|Abimelech destroyed the city of [[Shechem, he is said to have "[[salting the earth|sown salt on it," probably as a curse on anyone who would re-inhabit it (Judges 9:45). The [[Book of Job contains the first mention of salt as a condiment. "Can that which is unsavoury be eaten without salt? or is there any taste in the white of an egg?" (Job 6:6). In the [[New Testament, six verses mention salt. In the [[Sermon on the Mount, [[Jesus referred to his followers as the "[[Salt and Light|salt of the earth". [[Paul the Apostle|The apostle Paul also encouraged Christians to "let your conversation be always full of grace, seasoned with salt" (Colossians 4:6). Salt is mandatory in the rite of the [[Tridentine Mass.[[s:Catholic Encyclopedia (1913)/Salt Salt is used in the third item (which includes an [[Exorcism) of the Celtic Consecration (''cf.'' [[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 [[Judaism, it is recommended to have either a salty bread or to add salt to the bread if this bread is unsalted when doing [[Kiddush for [[Shabbat. It is customary to spread some salt over the bread or to dip the bread in a little salt when passing the bread around the table after the Kiddush. To preserve the covenant between their people and God, Jews dip the [[Sabbath bread in salt. In [[Wicca, salt is symbolic of the element Earth. It is also believed to cleanse an area of harmful or negative energies. A dish of salt and a dish of water are almost always present on an [[altar, and salt is used in a wide variety of rituals and ceremonies.


References

{{Good article [[Category:Edible salt| [[Category:Food additives [[Category:Sodium minerals [[Category:Objects believed to protect from evil