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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 ...
composed primarily of sodium chloride (NaCl), a
chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
belonging to the larger class of
salts In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively c ...
; salt in the form of a natural
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, macros ...
mineral is known as rock salt or
halite Halite (), 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 ...
. 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, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has appr ...
. The open ocean has about of solids per liter of sea water, a salinity of 3.5%. 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 ...
is one of the basic human tastes. Salt is one of the oldest and most ubiquitous food seasonings, and is known to uniformly improve the taste perception of food, including otherwise unpalatable food. Salting,
brining In food processing, brining is treating food with brine or coarse salt which preserves and seasons the food while enhancing tenderness and flavor with additions such as herbs, spices, sugar, caramel or vinegar. Meat and fish are typically ...
, and
pickling Pickling is the process of preserving or extending the shelf life of food by either anaerobic fermentation in brine or immersion in vinegar. The pickling procedure typically affects the food's texture and flavor. The resulting food is cal ...
are also ancient and important methods of 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 A spring is a point of exit at which groundwater from an aquifer flows out on top of Earth's crust ( pedosphere) and becomes surface water. It is a component of the hydrosphere. Springs have long been important for humans as a source of fresh ...
to extract salts; a salt-works in China dates to approximately the same period. Salt was also prized by the ancient
Hebrews The terms ''Hebrews'' (Hebrew: / , Modern: ' / ', Tiberian: ' / '; ISO 259-3: ' / ') and ''Hebrew people'' are mostly considered synonymous with the Semitic-speaking Israelites, especially in the pre-monarchic period when they were still ...
,
Greeks The Greeks or Hellenes (; el, Έλληνες, ''Éllines'' ) are an ethnic group and nation indigenous to the Eastern Mediterranean and the Black Sea regions, namely Greece, Cyprus, Albania, Italy, Turkey, Egypt, and, to a lesser extent, oth ...
,
Romans Roman or Romans most often 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 lette ...
, Byzantines,
Hittites The Hittites () were an Anatolian people who played an important role in establishing first a kingdom in Kussara (before 1750 BC), then the Kanesh or Nesha kingdom (c. 1750–1650 BC), and next an empire centered on Hattusa in north-centra ...
, Egyptians, and Indians. Salt became an important article of trade and was transported by boat across the
Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ...
, along specially built
salt road A salt road (also known as a salt route, salt way, saltway, or salt trading route) refers to any of the prehistoric and historical trade routes by which essential salt was transported to regions that lacked it. From the Bronze Age (in the 2nd m ...
s, and across the Sahara on
camel caravan A camel train or caravan is a series of camels carrying passengers and goods on a regular or semi-regular service between points. Despite rarely travelling faster than human walking speed, for centuries camels' ability to withstand harsh condi ...
s. The scarcity and universal need for salt have led nations to go to war over it and use it to raise
tax A tax is a compulsory financial charge or some other type of levy imposed on a taxpayer (an individual or legal entity) by a governmental organization in order to fund government spending and various public expenditures (regional, local, or n ...
revenues. Salt is used in religious ceremonies and has other cultural and traditional significance. Salt is processed from
salt mines Salt mining extracts natural salt deposits from underground. 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 combustio ...
, and by the 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 sa ...
) and mineral-rich spring water in shallow pools. Its major industrial products are
caustic soda Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly caustic base and alkali ...
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 i ...
; salt is used in many industrial processes including the manufacture of 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 adaptab ...
s,
paper pulp Pulp is a Lignocellulosic biomass, lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibers from wood, fiber crops, Paper recycling, waste paper, or cotton paper, rags. Mixed with water and other chemica ...
and many other products. Of the annual global production of around two hundred million
tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1000  kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
s of salt, about 6% is used for human consumption. Other uses include water conditioning processes,
de-icing Deicing is the process of removing snow, ice or frost from a surface. Anti-icing is the application of chemicals that not only deice but also remain on a surface and continue to delay the reformation of ice for a certain period of time, or prev ...
highways, and agricultural use. Edible salt is sold in forms such as sea salt and table salt which usually contains an
anti-caking agent An 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 ...
and may be 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 cong ...
. As well as its use in cooking and at the table, salt is present in many processed foods. Sodium is an essential nutrient for human health via its role as an electrolyte and 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, ...
, such as hypertension, in children and adults. Such
health effects of salt The health effects of salt are the conditions associated with the consumption of either too much or too little salt. Salt is a mineral composed primarily of sodium chloride (NaCl) and is used in food for both preservation and flavor. Sodium ions ...
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 states its main objective as "the attainment by all peoples of the highest possible level of ...
recommends that adults 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 a prehistoric town located in present-day Bulgaria, near the modern city of Provadia. Believed by archaeologists to be the oldest town in Europe, Solnitsata was a fortified stone settlement ...
, in
Bulgaria Bulgaria (; bg, България, Bǎlgariya), officially the Republic of Bulgaria,, ) is a country in Southeast Europe. It is situated on the eastern flank of the Balkans, and is bordered by Romania to the north, Serbia and North Macedo ...
, which was a salt mine, providing the area now known as the
Balkans The Balkans ( ), also known as the Balkan Peninsula, is a geographical area in southeastern Europe with various geographical and historical definitions. The region takes its name from the Balkan Mountains that stretch throughout the who ...
with salt since 5400 BC. Even the name Solnitsata means "salt works". While people have used canning and artificial
refrigeration The term refrigeration refers to the process of removing heat from an enclosed space or substance for the purpose of lowering the temperature.International Dictionary of Refrigeration, http://dictionary.iifiir.org/search.phpASHRAE Terminology, ht ...
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 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 Population In 2011, it had a population of 470,766 ...
, Romania. Evidence indicates that
Neolithic The Neolithic period, or New Stone Age, is an Old World archaeological period and the final division of the Stone Age. It saw the Neolithic Revolution, a wide-ranging set of developments that appear to have arisen independently in several p ...
people of the Precucuteni Culture were boiling the salt-laden spring water through the process of
briquetage Briquetage or very coarse pottery (VCP) is a coarse ceramic material used to make evaporation vessels and supporting pillars used in extracting salt from brine or seawater. Thick-walled saltpans were filled with saltwater and heated from belo ...
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 Yuncheng is the southernmost prefecture-level city in Shanxi province, People's Republic of China. It borders Linfen and Jincheng municipalities to the north and east, and Henan (Luoyang and Jiyuan to the east, Sanmenxia to the south) and Shaan ...
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.
Nomad A nomad is a member of a community without fixed habitation who regularly moves to and from the same areas. Such groups include hunter-gatherers, pastoral nomads (owning livestock), tinkers and trader nomads. In the twentieth century, the po ...
s 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 Salting the earth, or sowing with salt, is the ritual of spreading salt on the site of cities razed by conquerers. It originated as a curse on re-inhabitation in the ancient Near East and became a well-established folkloric motif in the Middle ...
: scattering salt around in a defeated city to prevent plant growth. The
Bible The Bible (from Koine Greek , , 'the books') is a collection of religious texts or scriptures that are held to be sacred in Christianity, Judaism, Samaritanism, and many other religions. The Bible is an anthologya compilation of texts ...
tells the story of King
Abimelech Abimelech (also spelled Abimelek or Avimelech; ) was the generic name given to all Philistine kings in the Hebrew Bible from the time of Abraham through King David. In the Book of Judges, Abimelech, son of Gideon, of the Tribe of Manasseh, i ...
who was ordered by God to do this at
Shechem Shechem ( ), also spelled Sichem ( ; he, שְׁכֶם, ''Šəḵem''; ; grc, Συχέμ, Sykhém; Samaritan Hebrew: , ), was a Canaanite and Israelite city mentioned in the Amarna Letters, later appearing in the Hebrew Bible as the first c ...
, and various texts claim that the
Roman Roman or Romans most often 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 lette ...
general
Scipio Aemilianus Africanus Publius Cornelius Scipio Africanus Aemilianus (185–129 BC), known as Scipio Aemilianus or Scipio Africanus the Younger, was a Roman general and statesman noted for his military exploits in the Third Punic War against Carthage and during the ...
ploughed over and sowed the city of
Carthage Carthage was the capital city of Ancient Carthage, on the eastern side of the Lake of Tunis in what is now Tunisia. Carthage was one of the most important trading hubs of the Ancient Mediterranean and one of the most affluent cities of the cla ...
with salt after it was defeated in the
Third Punic War The Third Punic War (149–146 BC) was the third and last of the Punic Wars fought between Carthage and Rome. The war was fought entirely within Carthaginian territory, in modern northern Tunisia. When the Second Punic War ended in 201  ...
(146 BC). Salt may have been used for
barter In trade, barter (derived from ''baretor'') is a system of exchange in which participants in a transaction directly exchange goods or services for other goods or services without using a medium of exchange, such as money. Economists disti ...
in connection with the obsidian trade in
Anatolia Anatolia, tr, Anadolu Yarımadası), and the Anatolian plateau, also known as Asia Minor, is a large peninsula in Western Asia and the westernmost protrusion of the Asian continent. It constitutes the major part of modern-day Turkey. The ...
in the
Neolithic Era The Neolithic period, or New Stone Age, is an Old World archaeological period and the final division of the Stone Age. It saw the Neolithic Revolution, a wide-ranging set of developments that appear to have arisen independently in several parts ...
. 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
Phoenicia Phoenicia () was an ancient thalassocratic civilization originating in the Levant region of the eastern Mediterranean, primarily located in modern Lebanon. The territory of the Phoenician city-states extended and shrank throughout their histor ...
ns in return for
Lebanon cedar ''Cedrus libani'', the cedar of Lebanon or Lebanese cedar (), is a species of tree in the genus cedrus, a part of the pine family, native to the mountains of the Eastern Mediterranean basin. It is a large evergreen conifer that has great relig ...
, glass, and the dye
Tyrian purple Tyrian purple ( grc, πορφύρα ''porphúra''; la, purpura), also known as Phoenician red, Phoenician purple, royal purple, imperial purple, or imperial dye, is a reddish-purple natural dye. The name Tyrian refers to Tyre, Lebanon. It i ...
; the Phoenicians traded Egyptian salted fish and salt from
North Africa North Africa, or Northern Africa is a region encompassing the northern portion of the African continent. There is no singularly accepted scope for the region, and it is sometimes defined as stretching from the Atlantic shores of Mauritania in ...
throughout their Mediterranean trade empire.
Herodotus Herodotus ( ; grc, , }; BC) was an ancient Greek historian and geographer A geographer is a physical scientist, social scientist or humanist whose area of study is geography, the study of Earth's natural environment and human society ...
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 to the capital. In Africa, salt was used as currency south of the Sahara, and slabs of rock salt were used as coins in
Abyssinia The Ethiopian Empire (), also formerly known by the exonym Abyssinia, or just simply known as Ethiopia (; Amharic and Tigrinya: ኢትዮጵያ , , Oromo: Itoophiyaa, Somali: Itoobiya, Afar: ''Itiyoophiyaa''), was an empire that historica ...
. The
Tuareg The Tuareg people (; also spelled Twareg or Touareg; endonym: ''Imuhaɣ/Imušaɣ/Imašeɣăn/Imajeɣăn'') are a large Berber ethnic group that principally inhabit the Sahara in a vast area stretching from far southwestern Libya to southern Alg ...
have traditionally maintained routes across the Sahara especially for the transportation of salt by
Azalai The Azalai (Tamasheq, var. Azalay) is a semi-annual salt caravan route practiced by Tuareg traders in the Sahara desert between Timbuktu and the Taoudenni salt mine in Mali, or the act of traveling with a caravan along that route. The other ...
(salt caravans). The caravans still cross the desert from southern Niger to
Bilma Bilma is an oasis town and commune in north east Niger with, as of the 2012 census, a total population of 4,016 people. It lies protected from the desert dunes under the Kaouar Cliffs and is the largest town along the Kaouar escarpment. It ...
, 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 late 1950s, sea salt was still the currency best appreciated in the interior.
Salzburg Salzburg (, ; literally "Salt-Castle"; bar, Soizbuag, label= Austro-Bavarian) is the fourth-largest city in Austria. In 2020, it had a population of 156,872. The town is on the site of the Roman settlement of ''Iuvavum''. Salzburg was founded ...
,
Hallstatt Hallstatt ( , , ) is a small town in the district of Gmunden, in the Austrian state of Upper Austria. Situated between the southwestern shore of Hallstätter See and the steep slopes of the Dachstein massif, the town lies in the Salzkammergut ...
, and
Hallein Hallein () is a historic town in the Austrian state of Salzburg. It is the capital of Hallein district. Geography The town is located in the ''Tennengau'' region south of the City of Salzburg, stretching along the Salzach river in the shadow of ...
lie within of each other on the river Salzach in central Austria in an area with extensive salt deposits.
Salzach The Salzach (Austrian: saltsax ) is a river in Austria and Germany. It is in length and is a right tributary of the Inn, which eventually joins the Danube. Its drainage basin of comprises large parts of the Northern Limestone and Central ...
literally means "salt river" and Salzburg "salt castle", both taking their names from the
German German(s) may refer to: * Germany (of or related to) ** Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ge ...
word meaning salt. Hallstatt was the site of the world's first
salt mine Salt mining extracts natural salt deposits from underground. 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 combustio ...
. 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
pickaxe A pickaxe, pick-axe, or pick is a generally T-shaped hand tool used for prying. Its head is typically metal, attached perpendicularly to a longer handle, traditionally made of wood, occasionally metal, and increasingly fiberglass. A stand ...
s and
shovel A shovel is a tool used for digging, lifting, and moving bulk materials, such as soil, coal, gravel, snow, sand, or ore. Most shovels are hand tools consisting of a broad blade fixed to a medium-length handle. Shovel blades are usually made o ...
s, began
open pan salt making Open-pan salt making is a method of salt production wherein salt is extracted from brine using open pans. Virtually all European domestic salt is obtained by solution-mining of underground salt formations, although some is still obtained by t ...
. During the first millennium BC, Celtic communities grew rich trading salt and salted meat to
Ancient Greece Ancient Greece ( el, Ἑλλάς, Hellás) was a northeastern Mediterranean Sea, Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of Classical Antiquity, classical antiquity ( AD 600), th ...
and
Ancient Rome In modern historiography, ancient Rome refers to Roman civilisation from the founding of the city of Rome in the 8th century BC to the collapse of the Western Roman Empire in the 5th century AD. It encompasses the Roman Kingdom (753–509 BC ...
in exchange for wine and other luxuries. The word ''
salary A salary is a form of periodic payment from an employer to an employee, which may be specified in an employment contract. It is contrasted with piece wages, where each job, hour or other unit is paid separately, rather than on a periodic basis. F ...
'' comes from the
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
word for salt. The reason for this is unknown; a persistent modern claim that the
Roman Legion The Roman legion ( la, legiō, ) was the largest military unit of the Roman army, composed of 5,200 infantry and 300 equites (cavalry) in the period of the Roman Republic (509 BC–27 BC) and of 5,600 infantry and 200 auxilia in the period o ...
s were sometimes paid in salt is baseless. The word ''salad'' literally means "salted", and comes from the ancient Roman practice of salting
leaf vegetable Leaf vegetables, also called leafy greens, pot herbs, vegetable greens, or simply greens, are plant leaves eaten as a vegetable, sometimes accompanied by tender petioles and shoots. Leaf vegetables eaten raw in a salad can be called salad gre ...
s. Wars have been fought over salt.
Venice Venice ( ; it, Venezia ; vec, Venesia or ) is a city in northeastern Italy and the capital of the Veneto region. It is built on a group of 118 small islands that are separated by canals and linked by over 400 bridges. The isla ...
fought and won a war with
Genoa Genoa ( ; it, Genova ; lij, Zêna ). is the capital of the Italian region of Liguria and the sixth-largest city in Italy. In 2015, 594,733 people lived within the city's administrative limits. As of the 2011 Italian census, the Province of ...
over the product, and it played an important part in the
American Revolution The American Revolution was an ideological and political revolution that occurred in British America between 1765 and 1791. The Americans in the Thirteen Colonies formed independent states that defeated the British in the American Revoluti ...
. Cities on overland trade routes grew rich by levying
duties A duty (from "due" meaning "that which is owing"; fro, deu, did, past participle of ''devoir''; la, debere, debitum, whence "debt") is a commitment or expectation to perform some action in general or if certain circumstances arise. A duty may ...
, and towns like
Liverpool Liverpool is a city and metropolitan borough in Merseyside, England. With a population of in 2019, it is the 10th largest English district by population and its metropolitan area is the fifth largest in the United Kingdom, with a populat ...
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 Christopher Columbus * lij, Cristoffa C(or)ombo * es, link=no, Cristóbal Colón * pt, Cristóvão Colombo * ca, Cristòfor (or ) * la, Christophorus Columbus. (; born between 25 August and 31 October 1451, died 20 May 1506) was a ...
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 The French Revolution ( ) was a period of radical political and societal change in France that began with the Estates General of 1789 and ended with the formation of the French Consulate in coup of 18 Brumaire, November 1799. Many of its ...
. After being repealed, this tax was reimposed by
Napoleon Napoleon Bonaparte ; it, Napoleone Bonaparte, ; co, Napulione Buonaparte. (born Napoleone Buonaparte; 15 August 1769 – 5 May 1821), later known by his regnal name Napoleon I, was a French military commander and political leader who ...
when he became emperor to pay for his foreign wars, and was not finally abolished until 1946. In 1930,
Mahatma Gandhi Mohandas Karamchand Gandhi (; ; 2 October 1869 – 30 January 1948), popularly known as Mahatma Gandhi, was an Indian lawyer, anti-colonial nationalist Quote: "... marks Gandhi as a hybrid cosmopolitan figure who transformed ... anti- ...
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 colonial salt tax. This act of civil disobedience inspired numerous Indians and transformed the
Indian independence movement The Indian independence movement was a series of historic events with the ultimate aim of ending British Raj, British rule in India. It lasted from 1857 to 1947. The first nationalistic revolutionary movement for Indian independence emerged ...
from an elitist one with little popular support into a national struggle.


Chemistry

Salt is mostly sodium chloride (NaCl).
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 sa ...
and mined salt may contain
trace element __NOTOC__ A trace element, also called minor element, is a chemical element whose concentration (or other measure of amount) is very low (a "trace amount"). They are classified into two groups: essential and non-essential. Essential trace elements ...
s. Mined salt is often refined. Salt crystals are translucent and cubic in shape; they normally appear white but impurities may give them a blue or purple tinge. When dissolved in water sodium chloride separates into Na+ and Cl ions, and the solubility is 359 grams per litre. From cold solutions, salt crystallises as the
dihydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...
NaCl·2H2O. Solutions of sodium chloride have very different properties from those of pure water; the
freezing point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depend ...
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).


Edible salt

Salt is essential to the health of humans and other animals, and it is one of the five basic taste sensations. Salt is used in many cuisines, and it is often found in
salt shaker Salt and pepper shakers or salt and pepper pots, of which the first item is normally called a salt cellar in British English, are condiment dispensers used in Western culture that are designed to allow diners to distribute grains of edible salt ...
s 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. Usually,
anticaking agents An 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 d ...
such as sodium aluminosilicate or magnesium carbonate are added to make it free-flowing.
Iodized salt Iodised salt ( also spelled iodized salt) is table salt mixed with a minute amount of various salts of the element iodine. The ingestion of iodine prevents iodine deficiency. Worldwide, iodine deficiency affects about two billion people and is t ...
, containing
potassium iodide Potassium iodide is a chemical compound, medication, and dietary supplement. It is a medication used for treating hyperthyroidism, in radiation emergencies, and for protecting the thyroid gland when certain types of radiopharmaceuticals are u ...
, is widely available. Some people put a desiccant, such as a few grains of uncooked
rice Rice is the seed of the grass species '' Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima'' (African rice). The name wild rice is usually used for species of the genera '' Zizania'' and '' Porteresia'', both wild and domesticat ...
or a
saltine cracker A saltine or soda cracker is a thin, usually square cracker usually made from white flour, sometimes yeast (although many are yeast free), and baking soda, with most varieties lightly sprinkled with coarse salt. It has perforations over its sur ...
, 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 that address a variety of health concerns, especially in the developing world. The identities and amounts of additives vary from country to country. Iodine is an important micronutrient for humans, and a
deficiency A deficiency is generally a lack of something. It may also refer to: *A deficient number, in mathematics, a number ''n'' for which ''σ''(''n'') < 2''n'' * thyroxine File:Thyroid_system.svg, upright=1.5, The thyroid system of the thyroid hormones T3 and T4 rect 376 268 820 433 Thyroid-stimulating hormone rect 411 200 849 266 Thyrotropin-releasing hormone rect 297 168 502 200 Hypothalamus rect 66 216 386 25 ...
( hypothyroidism) and enlargement of the thyroid gland (
endemic goitre Endemic goiter is a type of goitre that is associated with dietary iodine deficiency. Cause Some inland areas where soil and water lacks in iodine compounds and consumption of marine foods is low are known for higher incidence of goitre. In such ...
) in adults or
cretinism Congenital iodine deficiency syndrome is a medical condition present at birth marked by impaired physical and mental development, due to insufficient thyroid hormone (hypothyroidism) often caused by insufficient dietary iodine during pregnancy. It ...
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 Potassium iodide is a chemical compound, medication, and dietary supplement. It is a medication used for treating hyperthyroidism, in radiation emergencies, and for protecting the thyroid gland when certain types of radiopharmaceuticals are u ...
,
sodium iodide Sodium iodide (chemical formula NaI) is an ionic compound formed from the chemical reaction of sodium metal and iodine. Under standard conditions, it is a white, water-soluble solid comprising a 1:1 mix of sodium cations (Na+) and iodide anions ...
, or
sodium iodate Sodium iodate ( Na I O3) is the sodium salt of iodic acid. Sodium iodate is an oxidizing agent. It has few uses. Preparation It can be prepared by the reacting a sodium-containing base such as sodium hydroxide with iodic acid, for example: : ...
. 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 Intellectual disability (ID), also known as general learning disability in the United Kingdom and formerly mental retardation, Rosa's Law, Pub. L. 111-256124 Stat. 2643(2010). is a generalized neurodevelopmental disorder characterized by signifi ...
. 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. In the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
, the
Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...
(FDA) recommends 150
micrograms In the metric system, a microgram or microgramme is a unit of mass equal to one millionth () of a gram. The unit symbol is μg according to the International System of Units (SI); the recommended symbol in the United States and United Kingdom wh ...
of iodine per day for both men and women. US iodized salt contains 46–77 ppm (parts per million), whereas in the UK the recommended iodine content of iodized salt is 10–22 ppm.
Sodium ferrocyanide Sodium ferrocyanide is the sodium salt of the coordination compound of formula e(CN)6sup>4−. In its hydrous form, Na4Fe(CN)6 ( sodium ferrocyanide decahydrate), it is sometimes known as yellow prussiate of soda. It is a yellow crystalline ...
, also known as yellow
prussiate {{Short pages monitor ...
of soda, is sometimes added to salt as an anticaking agent. 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 The Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment (COT) is a UK independent scientific committee that provides advice to the Food Standards Agency, the Department of Health and other Government Departments and A ...
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 Tricalcium phosphate (sometimes abbreviated TCP) is a calcium salt of phosphoric acid with the chemical formula Ca3(PO4)2. It is also known as tribasic calcium phosphate and bone phosphate of lime (BPL). It is a white solid of low solubility. Mo ...
,
calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...
or magnesium carbonates,
fatty acid In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, ...
salts (
acid salt Acid salts are a class of salts that produce an acidic solution after being dissolved in a solvent. Its formation as a substance has a greater electrical conductivity than that of the pure solvent. An acidic solution formed by acid salt is made dur ...
s),
magnesium oxide Magnesium oxide ( Mg O), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2− ions ...
,
silicon dioxide Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...
, calcium silicate, sodium aluminosilicate and
calcium aluminosilicate Calcium aluminosilicate, an aluminosilicate compound with calcium cations, most typically has formula CaAl2Si2O8. In minerals, as a feldspar, it can be found as anorthite, an end-member of the plagioclase Plagioclase is a series of tecto ...
. Both the European Union and the United States Food and Drug Administration permitted the use of
aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
in the latter two compounds. In "doubly fortified salt", both iodide and iron salts are added. The latter alleviates
iron deficiency anaemia Iron-deficiency anemia is anemia caused by a lack of iron. Anemia is defined as a decrease in the number of red blood cells or the amount of hemoglobin in the blood. When onset is slow, symptoms are often vague such as feeling tired, weak, shor ...
, which interferes with the mental development of an estimated 40% of infants in the developing world. A typical iron source is ferrous fumarate. Another additive, especially important for pregnant women, is
folic acid Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dietary supplement and in food fortification as it is more stable during processing and ...
(vitamin B9), which gives the table salt a yellow color. Folic acid helps prevent
neural tube defect Neural tube defects (NTDs) are a group of birth defects in which an opening in the spine or cranium remains from early in human development. In the third week of pregnancy called gastrulation, specialized cells on the dorsal side of the embryo b ...
s and anaemia, which affect young mothers, especially in developing countries. A lack of fluoride in the diet is the cause of a greatly increased incidence of
dental caries Tooth decay, also known as cavities or caries, is the breakdown of teeth due to acids produced by bacteria. The cavities may be a number of different colors from yellow to black. Symptoms may include pain and difficulty with eating. Complicat ...
. 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 Water fluoridation is the controlled adjustment of fluoride to a public water supply solely to reduce tooth decay. Fluoridated water contains fluoride at a level that is effective for preventing cavities; this can occur naturally or by adding ...
is not carried out. In
France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...
, 35% of the table salt sold contains added
sodium fluoride Sodium fluoride (NaF) is an inorganic compound with the formula . It is used in trace amounts in the fluoridation of drinking water, in toothpaste, in metallurgy, and as a flux. It is a colorless or white solid that is readily soluble in water. I ...
.


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 sa ...
contains small amounts of
magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
and
calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...
halides In chemistry, a halide (rarely halogenide) is a binary chemical compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a fluor ...
and
sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...
s, traces of 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 Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substan ...
(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 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 diseases. Salts have diverse mineralities depending on their source, giving each one a unique flavour.
Fleur de sel ''Fleur de sel'' ("flower of salt" in French; ) or ''flor de sal'' (also "flower of salt" in Portuguese, Spanish and Catalan) is a salt that forms as a thin, delicate crust on the surface of seawater as it evaporates. ''Fleur de sel'' has been c ...
, a natural sea salt from the surface of evaporating brine in salt pans, has a distinctive flavour varying with its source. In traditional Korean cuisine, so-called " bamboo salt" is prepared by roasting salt in a
bamboo Bamboos are a diverse group of evergreen perennial flowering plants making up the subfamily Bambusoideae of the grass family Poaceae. Giant bamboos are the largest members of the grass family. The origin of the word "bamboo" is uncertain, ...
container plugged with mud at both ends. This product absorbs minerals from the bamboo and the mud, and has been claimed to increase the anticlastogenic and antimutagenic properties of
doenjang ''Doenjang'' * (; "thick sauce") or soybean paste is a type of fermented bean paste made entirely of soybean and brine. It is also a byproduct of soup soy sauce production. It is sometimes used as a relish. History The earliest soybean fer ...
(a fermented bean paste). Kosher or kitchen salt has a larger grain size than table salt and is used in cooking. It can be useful for
brining In food processing, brining is treating food with brine or coarse salt which preserves and seasons the food while enhancing tenderness and flavor with additions such as herbs, spices, sugar, caramel or vinegar. Meat and fish are typically ...
, bread or pretzel making and as a scrubbing agent when combined with oil.
Pickling salt Pickling salt is a salt that is used mainly for canning and manufacturing pickles. It is sodium chloride, as is table salt, but unlike most brands of table salt, it does not contain iodine or any anti caking products added. A widely circulated ...
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 canned foods and especially
salted foods Salting is the preservation of food with dry edible salt.
,
pickled foods Pickling is the process of preserving or extending the shelf life of food by either anaerobic fermentation in brine or immersion in vinegar. The pickling procedure typically affects the food's texture and flavor. The resulting food is calle ...
, and snack foods or other
convenience food Convenience food, also called tertiary processed food, is food that is commercially prepared (often through processing) to optimise ease of consumption. Such food is usually ready to eat without further preparation. It may also be easily p ...
s), where it functions as both a
preservative A preservative is a substance or a chemical that is added to products such as food products, beverages, pharmaceutical drugs, paints, biological samples, cosmetics, wood, and many other products to prevent decomposition by microbial growth or by ...
and a
flavoring A flavoring (or flavouring), also known as flavor (or flavour) or flavorant, is a food additive used to improve the taste or smell of food. It changes the perceptual impression of food as determined primarily by the chemoreceptors of the gus ...
.
Dairy salt Dairy salt is a culinary salt (sodium chloride) product used in the preparation of butter and cheese products that serves to add flavor and act as a food preservative. Dairy salt can vary in terms of quality and purity, with purer varieties be ...
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 refers to the process of removing heat from an enclosed space or substance for the purpose of lowering the temperature.International Dictionary of Refrigeration, http://dictionary.iifiir.org/search.phpASHRAE Terminology, ht ...
, salting was one of the main methods of food preservation. Thus, herring contains 67 mg sodium per 100 g, while
kipper A kipper is a whole herring, a small, oily fish, that has been split in a butterfly fashion from tail to head along the dorsal ridge, gutted, salted or pickled, and cold-smoked over smouldering wood chips (typically oak). In the United Ki ...
, its preserved form, contains 990 mg. Similarly,
pork Pork is the culinary name for the meat of the domestic pig (''Sus domesticus''). It is the most commonly consumed meat worldwide, with evidence of pig husbandry dating back to 5000 BCE. Pork is eaten both freshly cooked and preserved; ...
typically contains 63 mg while bacon contains 1,480 mg, and
potato The potato is a starchy food, a tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial in the nightshade family Solanaceae. Wild potato species can be found from the southern Unit ...
es contain 7 mg but
potato crisp A potato chip (North American English; often just chip) or crisp (British and Irish English) is a thin slice of potato that has been either deep fried, baked, or air fried until crunchy. They are commonly served as a snack, side dish, or ap ...
s 800 mg per 100 g. Salt is also used extensively in cooking as a flavoring, and cooking techniques such as with
salt crust A salt crust is a method of cooking by completely covering an ingredient such as fish, chicken or vegetables in salt (sometimes bound together by water or egg white) before baking. The salt layer acts as insulation and helps cook the food in an e ...
s and
brining In food processing, brining is treating food with brine or coarse salt which preserves and seasons the food while enhancing tenderness and flavor with additions such as herbs, spices, sugar, caramel or vinegar. Meat and fish are typically ...
. 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 Fish sauce is a liquid condiment made from fish or krill that have been coated in salt and fermented for up to two years. It is used as a staple seasoning in East Asian cuisine and Southeast Asian cuisine, particularly Myanmar, Cambodia, Lao ...
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 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 ...
is detected by sodium
taste receptor A taste receptor or tastant is a type of cellular receptor which facilitates the sensation of taste. When food or other substances enter the mouth, molecules interact with saliva and are bound to taste receptors in the oral cavity and other loc ...
s present in taste bud cells on the tongue. Human sensory taste testing studies have shown that 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 osmotic regulation of water content in body organs (
fluid balance Fluid balance is an aspect of the homeostasis of organisms in which the amount of water in the organism needs to be controlled, via osmoregulation and behavior, such that the concentrations of electrolytes ( salts in solution) in the various b ...
). Most of the sodium in the
Western diet The Western pattern diet is a modern dietary pattern that is generally characterized by high intakes of pre-packaged foods, refined grains, red meat, processed meat, high-sugar drinks, candy and sweets, fried foods, conventionally-raised anim ...
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. 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 states its main objective as "the attainment by all peoples of the highest possible level of ...
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 ethnicities. 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. Evidence shows a more complicated relationship between salt and cardiovascular disease. "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 (equivalent to 10-13 g salt) a day. One of the two most prominent dietary risks for disability in the world are diets high in 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. Sodium chloride is one of the largest volume inorganic raw materials. Its major chemical products are
caustic soda Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly caustic base and alkali ...
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 i ...
. These are used in the manufacture of PVC,
paper pulp Pulp is a Lignocellulosic biomass, lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibers from wood, fiber crops, Paper recycling, waste paper, or cotton paper, rags. Mixed with water and other chemica ...
and many other inorganic and organic compounds. Salt is also used as a flux in the production of
aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
. 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
soap Soap is a salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, soaps are use ...
s and
glycerine Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...
, where it is used to saponify fats. As an emulsifier, salt is used in the manufacture of synthetic rubber, and another use is in the firing of
pottery Pottery is the process and the products of forming vessels and other objects with clay and other ceramic materials, which are fired at high temperatures to give them a hard and durable form. Major types include earthenware, stoneware and ...
, when salt added to the furnace vaporises before condensing onto the surface of the ceramic material, forming a strong glaze. When drilling through loose materials such as sand or gravel, salt may be added to the
drilling fluid In geotechnical engineering, drilling fluid, also called drilling mud, is used to aid the drilling of boreholes into the earth. Often used while drilling oil and natural gas wells and on exploration drilling rigs, drilling fluids are als ...
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 A mordant or dye fixative is a substance used to set (i.e. bind) dyes on fabrics by forming a coordination complex with the dye, which then attaches to the fabric (or tissue). It may be used for dyeing fabrics or for intensifying stains in ...
in
textile Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not the ...
dying, to regenerate
resin In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on n ...
s in water softening, for the
tanning Tanning may refer to: *Tanning (leather), treating animal skins to produce leather *Sun tanning, using the sun to darken pale skin **Indoor tanning, the use of artificial light in place of the sun **Sunless tanning, application of a stain or dye t ...
of hides, the preservation of meat and fish and the canning of meat and vegetables.


Production

Food-grade salt accounts for only a small part of salt production in 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 unit of mass equal to 1000  kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
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 of approximately 3.5%. This means that there are about of dissolved salts, predominantly
sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...
() and
chloride The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride sa ...
()
ions An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
, 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 pond A salt evaporation pond is a shallow artificial salt pan designed to extract salts from sea water or other brines. The Salt pans are shallow and large of size because it will be easier for sunlight to travel and reach the sea water. Natural sal ...
s 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 sources are either mined directly, producing rock salt, or are extracted by pumping water into the deposit. In either case, the salt may be purified by mechanical evaporation of brine. Traditionally, purification was achieved in shallow open pans that were heated to accelerate evaporation.
Vacuum A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or " void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often di ...
-based methods are also employed. The raw salt is refined by treatment with chemicals that precipitate most impurities (largely magnesium and calcium salts). Multiple stages of evaporation are then applied. Some salt is produced using the
Alberger process The Alberger process is an industrial method of producing salt from rock salt. Method The Alberger process begins by heating brine under high pressure with a series of heaters. Impurities are removed using a tank filled with granite cubes called ...
, which involves vacuum pan evaporation combined with the seeding of the solution with cubic crystals, and produces a grainy-type flake. The
Ayoreo The Ayoreo (Ayoreode, Ayoréo, Ayoréode) are an indigenous people of the Gran Chaco. They live in an area surrounded by the Paraguay, Pilcomayo, Parapetí, and Grande Rivers, spanning both Bolivia and Paraguay. There are approximately 5,600 ...
, an indigenous group from the Paraguayan Chaco, obtain their salt from the ash produced by burning the timber of the Indian salt tree (''
Maytenus vitis-idaea ''Maytenus'' ''Sunset Western Garden Book,'' 1995:606–607 is a genus of flowering plants in the family Celastraceae. Members of the genus are distributed throughout Central and South America, Southeast Asia, Micronesia and Australasia, the Indi ...
'') and other trees. One of the largest salt mining operations in the world is at the
Khewra Salt Mine The Khewra Salt Mine (or Mayo Salt Mine) is in Khewra, north of Pind Dadan Khan, an administrative subdivision of Jhelum District, Punjab Region, Pakistan. The mine is in the Salt Range, Potohar plateau, which rises from the Indo-Gangetic Pla ...
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 Room and pillar or pillar and stall is a variant of breast stoping. It is a mining system in which the mined material is extracted across a horizontal plane, creating horizontal arrays of rooms and pillars. To do this, "rooms" of ore are dug out ...
method, where about half the material is left in place to support the upper levels. Extraction of
Himalayan salt Himalayan salt is rock salt (halite) mined from the Punjab region of Pakistan. The salt, which often has a pinkish tint due to trace minerals, is primarily used as a food additive to replace refined table salt but is also used for cooking and fo ...
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 Brahmanic sacrifices, in Hittite rituals and during festivals held by
Semites Semites, Semitic peoples or Semitic cultures is an obsolete term for an ethnic, cultural or racial group.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 Holy water is water that has been blessed by a member of the clergy or a religious figure, or derived from a well or spring considered holy. The use for cleansing prior to a baptism and spiritual cleansing is common in several religions, from ...
in the Christian faith. In
Aztec The Aztecs () were a Mesoamerican culture that flourished in central Mexico in the post-classic period from 1300 to 1521. The Aztec people included different ethnic groups of central Mexico, particularly those groups who spoke the Nahuatl ...
mythology,
Huixtocihuatl In Aztec religion, Huixtocihuatl (or Uixtochihuatl, Uixtociuatl) was a fertility goddess who presided over salt and salt water. The Aztecs considered her to be the older sister of the rain gods, including Tlaloc. Much of the information known abou ...
was a fertility goddess who presided over salt and salt water. Salt is considered to be a very auspicious substance in
Hinduism Hinduism () is an Indian religion or '' dharma'', a religious and universal order or way of life by which followers abide. As a religion, it is the world's third-largest, with over 1.2–1.35 billion followers, or 15–16% of the global p ...
and is used in particular religious ceremonies like house-warmings and weddings. In
Jainism Jainism ( ), also known as Jain Dharma, is an Indian religion. Jainism traces its spiritual ideas and history through the succession of twenty-four tirthankaras (supreme preachers of ''Dharma''), with the first in the current time cycle bein ...
, 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 Buddhist ''Mahāyāna'' (; "Great Vehicle") is a term for a broad group of Buddhist traditions, texts, philosophies, and practices. Mahāyāna Buddhism developed in India (c. 1st century BCE onwards) and is considered one of the three main existing br ...
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 Shinto () is a religion from Japan. Classified as an East Asian religion by scholars of religion, its practitioners often regard it as Japan's indigenous religion and as a nature religion. Scholars sometimes call its practitioners ''Shintois ...
, is used for
ritual purification Ritual purification is the ritual prescribed by a religion by which a person is considered to be free of ''uncleanliness'', especially prior to the worship of a deity, and ritual purity is a state of ritual cleanliness. Ritual purification may ...
of locations and people (
harae or ( or ) is the general term for ritual purification in Shinto. is one of four essential elements involved in a Shinto ceremony. The purpose is the purification of pollution or sins () and uncleanness ().(Norbeck, 1952) These concepts include ...
, 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 The Hebrew Bible or Tanakh (;"Tanach"
'' mention salt. One of these mentions
Lot's wife In the Bible, Lot's wife is a figure first mentioned in . The Book of Genesis describes how she became a pillar of salt after she looked back at Sodom. She is not named in the Bible but is called "Ado" or "Edith" in some Jewish traditions. She ...
, who was turned into a pillar of salt when she looked back at the cities of Sodom and Gomorrah (
Genesis Genesis may refer to: Bible * Book of Genesis, the first book of the biblical scriptures of both Judaism and Christianity, describing the creation of the Earth and of mankind * Genesis creation narrative, the first several chapters of the Book of ...
19:26) as they were destroyed. When the judge
Abimelech Abimelech (also spelled Abimelek or Avimelech; ) was the generic name given to all Philistine kings in the Hebrew Bible from the time of Abraham through King David. In the Book of Judges, Abimelech, son of Gideon, of the Tribe of Manasseh, i ...
destroyed the city of
Shechem Shechem ( ), also spelled Sichem ( ; he, שְׁכֶם, ''Šəḵem''; ; grc, Συχέμ, Sykhém; Samaritan Hebrew: , ), was a Canaanite and Israelite city mentioned in the Amarna Letters, later appearing in the Hebrew Bible as the first c ...
, he is said to have " 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 The New Testament grc, Ἡ Καινὴ Διαθήκη, transl. ; la, Novum Testamentum. (NT) is the second division of the Christian biblical canon. It discusses the teachings and person of Jesus, as well as events in first-century Chri ...
, six verses mention salt. In the Sermon on the Mount,
Jesus Jesus, likely from he, יֵשׁוּעַ, translit=Yēšūaʿ, label= Hebrew/ Aramaic ( AD 30 or 33), also referred to as Jesus Christ or Jesus of Nazareth (among other names and titles), was a first-century Jewish preacher and religiou ...
referred to his followers as the " salt of the earth".
The apostle Paul Paul; grc, Παῦλος, translit=Paulos; cop, ⲡⲁⲩⲗⲟⲥ; hbo, פאולוס השליח (previously called Saul of Tarsus;; ar, بولس الطرسوسي; grc, Σαῦλος Ταρσεύς, Saũlos Tarseús; tr, Tarsuslu Pavlus; ...
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 The Tridentine Mass, also known as the Traditional Latin Mass or Traditional Rite, is the liturgy of Mass in the Roman Rite of the Catholic Church that appears in typical editions of the Roman Missal published from 1570 to 1962. Celebrated almo ...
. s:Catholic Encyclopedia (1913)/Salt Salt is used in the third item (which includes an
Exorcism Exorcism () is the religious or spiritual practice of evicting demons, jinns, or other malevolent spiritual entities from a person, or an area, that is believed to be possessed. Depending on the spiritual beliefs of the exorcist, this may be ...
) of the Celtic Consecration (''cf.''
Gallican Rite The Gallican Rite is a historical version of Christian liturgy and other ritual practices in Western Christianity. It is not a single rite but a family of rites within the Latin Church, which comprised the majority use of most of Western Christia ...
) 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 Judaism ( he, ''Yahăḏūṯ'') is an Abrahamic, monotheistic, and ethnic religion comprising the collective religious, cultural, and legal tradition and civilization of the Jewish people. It has its roots as an organized religion in t ...
, 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 Wicca () is a modern Pagan religion. Scholars of religion categorise it as both a new religious movement and as part of the occultist stream of Western esotericism. It was developed in England during the first half of the 20th century and w ...
, 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 An altar is a table or platform for the presentation of religious offerings, for sacrifices, or for other ritualistic purposes. Altars are found at shrines, temples, churches, and other places of worship. They are used particularly in paga ...
, and salt is used in a wide variety of rituals and ceremonies.


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