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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 salt (chemistry), salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With Molar mass, molar ...
(NaCl), a
chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by chemical bonds. A homonuclear molecule, m ...
belonging to the larger class of
salts In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atoms, ...
; salt in the form of a natural
crystalline A crystal or crystalline solid is a solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the least amount of kinet ...
mineral is known as rock salt or
halite Halite (), commonly known as rock salt, is a type of salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crysta ...

halite
. Salt is present in vast quantities in
seawater Seawater, or salt water, is water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of E ...

seawater
. The open ocean has about of solids per liter of sea water, a
salinity Salinity () is the saltiness or amount of dissolved in a body of , called (see also ). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal to ‰). Salinity is an important ...

salinity
of 3.5%. Salt is essential for life in general, and
saltiness The gustatory system or sense of taste is the sensory system The sensory nervous system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory neurons (including the sensory re ...
is one of the basic human tastes. Salt is one of the oldest and most ubiquitous food
seasoning Seasoning is the process of adding herbs In general use, herbs are a widely distributed and widespread group of plants, excluding vegetables Vegetables are parts of plants that are consumed by humans or other animals as food. The origina ...

seasoning
s, and 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 redox, oxidation of fats that cause Ran ...

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. Springs have long been important for humans as a source of water, especially in arid regions which ...
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 Hebrew (, , or ) is a Northwest Semitic languages, Northwest Semitic language of the Afroasiatic languages, Afroasiatic language family. Historically, it is regarded as the language of the Israelites, Jud ...

Hebrews
, the
Greeks The Greeks or Hellenes (; el, Έλληνες, ''Éllines'' ) are an ethnic group An ethnic group or ethnicity is a grouping of people A people is any plurality of person A person (plural people or persons) is a being that has cer ...
, the
Romans Roman or Romans usually refers to: *Rome , established_title = Founded , established_date = 753 BC , founder = King Romulus , image_map = Map of comune of Rome (metropolitan city of Capital Rome, region Lazio, ...
, the
Byzantines
Byzantines
, the
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 Hattusa (also ...

Hittites
,
Egyptians Egyptians ( arz, المصريين, ; cop, ⲣⲉⲙⲛ̀ⲭⲏⲙⲓ, remenkhēmi) are an ethnic group of people originating from the country of Egypt Egypt ( ar, مِصر, Miṣr), officially the Arab Republic of Egypt, is a spanning t ...

Egyptians
, and the
Indians Indian or Indians refers to people or things related to India, or to the indigenous people of the Americas, or Aboriginal Australians until the 19th century. People South Asia * Indian people, people of Indian nationality, or people who come ...

Indians
. Salt became an important article of trade and was transported by boat across the
Mediterranean Sea The Mediterranean Sea is a connected to the , surrounded by the and almost completely enclosed by land: on the north by and and , on the south by , and on the east by the . The Sea has played a central role in the . Although the Mediterrane ...
, along specially built salt roads, and across the
Sahara The Sahara (, ; ar, الصحراء الكبرى, ', 'the Greatest Desert') is a desert on the African continent Africa is the world's second-largest and second-most populous continent A continent is any of several large landma ...

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 A tax is a compulsory financial charge or some other type of levy imposed on a taxpayer (an individual or legal entity In law Law is a system A system is a group of Interaction, interacting or interrelated elements that act accord ...
revenues. Salt is used in religious ceremonies and has other cultural and traditional significance. Salt is processed from salt mines, and by the
evaporation Evaporation is a type of that occurs on the of a as it changes into the gas phase. The surrounding gas must not be saturated with the evaporating substance. When the molecules of the liquid collide, they transfer energy to each other bas ...

evaporation
of seawater (
sea salt Sea salt is salt 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 ...

sea salt
) and mineral-rich spring water in shallow pools. Its major industrial products are caustic soda and
chlorine Chlorine is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemica ...

chlorine
; salt is used in many industrial processes including the manufacture of
polyvinyl chloride Polyvinyl chloride (colloquial Colloquialism or colloquial language is the style (sociolinguistics), linguistic style used for casual (informal) communication. It is the most common functional style of speech, the idiom normally employed in ...
,
plastic Plastics are a wide range of syntheticA synthetic is an artificial material produced by organic chemistry, organic chemical synthesis. Synthetic may also refer to: In the sense of both "combination" and "artificial" * Synthetic chemical or s ...

plastic
s,
paper pulp Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fiber Cellulose fibers () are fibers made with ethers or esters of cellulose, which can be obtained from the bark, wood or leaves of plants, ...
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 kilogram The kilogram (also kilogramme) is the base unit of mass Mass is the physical quantity, quantity of ''matter'' in a physical body. It is also a meas ...
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 Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It cons ...

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 food additive, additive placed in powder (substance), powdered or granular material, granulated materials, such as table salt or confectioneries, to prevent the formation of lumps (Caking (chemical engineering), caking) and ...
and may be
iodised
iodised
to prevent
iodine deficiency Iodine deficiency is a lack of the mineral (nutrient), trace element iodine, an essential nutrient in the diet (nutrition), diet. It may result in metabolic problems such as goiter, sometimes as an endemic goiter as well as congenital iodine defi ...
. 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 Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition * Matter, anything that has mass and ta ...
for human health via its role as an
electrolyte An electrolyte is a medium containing ions that is electrically conducting Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that quantifies how strongly it resist ...

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 The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pumps blood through the blood vessels of the circulatory system. The pumped blood car ...
, such as
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a Chronic condition, long-term Disease, medical condition in which the blood pressure in the artery, arteries is persistently elevated. High blood pressure usually does not ...

hypertension
, in children and adults. Such
health effects of salt Health is a state of physical, mental and social well-being Well-being, also known as ''wellness'', ''prudential value'' or ''quality of life'', refers to what is intrinsically valuable relative ''to'' someone. So the well-being of a person ...
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 United Nations Specialized Agencies are autonomous organizations working with the United Nations and each other through the co-ordinating machinery of the Unit ...
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 , 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 ...

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 Europe is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rathe ...

Balkans
with salt since 5400 BC. Even the name Solnitsata means "salt works". While people have used
canning Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container (jar A jar is a rigid, cylindrical or slightly conical container, typically made of , , or , with a wide mouth or op ...

canning
and artificial
refrigeration The term refrigeration means cooling Cooling is removal of heat, usually resulting in a lower temperature and/or phase change. Temperature lowering achieved by any other means may also be called cooling.ASHRAE Terminology, https://www.ashrae.org/ ...

refrigeration
to preserve food for the last hundred years or so, salt has been the best-known food preservative, especially for meat, for many thousands of years. A very ancient salt-works operation has been discovered at the Poiana Slatinei archaeological site next to a salt spring in Lunca,
Neamț County Neamț County () is a county (județ) of Romania, in the Historical regions of Romania, historic region of Moldavia, with the county seat at Piatra Neamț. The county takes its name from the Neamț (Moldova), Neamț River. Demographics Populati ...
, Romania. Evidence indicates that
Neolithic The Neolithic period is the final division of the Stone Age The Stone Age was a broad prehistoric Prehistory, also known as pre-literary history, is the period of human history Human history, also known as world history, is t ...
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 A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing a nonmetallic mineral, such as clay, at a high temperatu ...

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 Xiechi Lake (), also called Yuncheng yanchi (Yuncheng Salt Lake) is the largest natural lake A lake is an area filled with water, localized in a Depression (geology), basin, surrounded by land, apart from any river or other outlet that serve ...
near
Yuncheng Yuncheng is the southernmost prefecture-level city A road sign shows distance to the "Huangshi urban area" () rather than simply " Yangxin County from the neighboring Xianning), but still from the Huangshi main urban area. A prefectural-l ...
in
Shanxi Shanxi (; ; Chinese postal romanization, formerly romanised as Shansi) is a landlocked Provinces of China, province of the China, People's Republic of China and is part of the North China region. The capital and largest city of the province is ...

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 ( frm, nomade "people without fixed habitation") is a member of a community without fixed habitation who regularly moves to and from the same areas. Such groups include hunter-gatherer A hunter-gatherer is a human Humans (''Homo ...

Nomad
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 Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form ...
: scattering salt around in a defeated city to prevent plant growth. The
Bible The Bible (from Koine Greek Koine Greek (, , Greek approximately ;. , , , lit. "Common Greek"), also known as Alexandrian dialect, common Attic, Hellenistic or Biblical Greek, was the koiné language, common supra-regional form of Gree ...

Bible
tells the story of King
Abimelech Abimelech (also spelled Abimelek or Avimelech; ) was the name of multiple mentioned in the . Etymology The name or title ''Abimelech'' is formed from Hebrew words for "father" and "king," and may be interpreted in a variety of ways, including ...

Abimelech
who was ordered by God to do this at
Shechem Shechem , also spelled Sichem (; he, שְׁכָם / Standard ''Šəḵem'' Tiberian ''Šeḵem'', "shoulder"; grc, Συχέμ LXX), was a Canaan A 1692 map of Canaan, by Philip Lea Canaan (; Northwest Semitic: ; Phoenician lang ...

Shechem
, and various texts claim that the
Roman Roman or Romans most often refers to: *, the capital city of Italy *, Roman civilization from 8th century BC to 5th century AD *, the people of ancient Rome *', shortened to ''Romans'', a letter in the New Testament of the Christian Bible Roman ...
general
Scipio Aemilianus Africanus Publius Cornelius Scipio Africanus Aemilianus (185–129 BC), primarily known as Scipio Aemilianus, was a Roman general and statesman noted for his military exploits in the Third Punic War The Third Punic War (149–146 BC) was the third a ...
ploughed over and sowed the city of
Carthage Carthage was the capital city of the ancient , on the eastern side of the in what is now . Carthage was the most important trading hub of the Ancient Mediterranean and one of the most affluent cities of the . The city developed from a n colony ...

Carthage
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 The Punic Wars were a series of wars (taking place between 264 and 146BC) that were fought between the Roman Republic The Roman Republic ( la, Rēs pūbli ...
(146 BC). Salt may have been used for
barter In trade, barter (derived from ''baretor'') is a system of exchange (economics), exchange in which participants in a financial transaction, transaction directly exchange good (economics), goods or service (economics), services for other goods or ...

barter
in connection with the
obsidian Obsidian (; ) is a naturally occurring volcanic glass formed when lava extrusive rock, extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock. Obsidian is produced from felsic lava, rich in the lighter element ...

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 makes up the majority of modern-day Turkey. The region ...
in the
Neolithic Era The Neolithic period is the final division of the Stone Age, with a wide-ranging set of developments that appear to have arisen independently in several parts of the world. It is first seen about 12,000 years ago when the first developments of ...
. Salt was included among funeral offerings found in
ancient Egypt Ancient Egypt was a civilization  A civilization (or civilisation) is a that is characterized by , , a form of government, and systems of communication (such as ). Civilizations are intimately associated with additional char ...

ancient Egypt
ian 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 Ancient history is the aggregate of past eventsWordNet Search – 3 ...
ns in return for
Lebanon cedar ''Cedrus libani'', the cedar of Lebanon or Lebanese cedar (), is a species of tree in the pine family Pinaceae, native species, native to the mountains of the Eastern Mediterranean basin. It is a large evergreen conifer that has great religious a ...
, 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 Purple is any of a variety of color Color (Ame ...
; 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 th ...

North Africa
throughout their Mediterranean trade empire.
Herodotus Herodotus ( ; grc, Ἡρόδοτος, Hēródotos, ; BC) was an Classical Greece, ancient Greek writer, geographer, and historian born in the Greek city of Halicarnassus, part of the Achaemenid Empire, Persian Empire (now Bodrum, Turkey). He ...
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 An endonym (from Greek: , 'inner' + , 'name'; also known as autonym) is a common, internal name A name is a term used for identification by an external observer. They can identify ...

Abyssinia
. The
Tuareg The Tuareg people (; also spelt Twareg or Touareg; endonym An endonym (from Greek: , 'inner' + , 'name'; also known as autonym) is a common, internal name A name is a term used for identification by an external observer. They can identify ...
have traditionally maintained routes across the
Sahara The Sahara (, ; ar, الصحراء الكبرى, ', 'the Greatest Desert') is a desert on the African continent Africa is the world's second-largest and second-most populous continent A continent is any of several large landma ...

Sahara
especially for the transportation of salt by
Azalai The Azalai ( Tamasheq, var. Azalay) is a semi-annual salt Camel train, caravan route practiced by Tuareg people, Tuareg traders in the Sahara desert between Timbuktu and the Taoudenni salt mine in Mali, or the act of traveling with a caravan along ...
(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, Kaouar Cliffs and is the largest town along the Kaouar escarpment ...
, although much of the trade now takes place by truck. Each camel takes two bales of
fodder Fodder (), also called provender (), is any agricultural Agriculture is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary Image:Family watching television 1958.jpg, Exercise ...

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=Bavarian language, Austro-Bavarian) is the List of cities and towns in Austria, fourth-largest city in Austria. In 2020, it had a population of 156,872. The town is on the site of the ...

Salzburg
,
Hallstatt Hallstatt ( , , ) is a small town in the district of Gmunden, in the Austria Austria (, ; german: Österreich ), officially the Republic of Austria (german: Republik Österreich, links=no, ), is a landlocked Eastern Alps, East Al ...

Hallstatt
, and
Hallein Hallein () is a historic town A town is a human settlement. Towns are generally larger than villages and smaller than city, cities, though the criteria to distinguish between them vary considerably in different parts of the world. O ...

Hallein
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 a right tributary of the Inn (river), Inn and is in length, its flow eventually joins the Danube. Its drainage basin of comprises large parts of the Northern Limest ...

Salzach
literally means "salt river" and Salzburg "salt castle", both taking their names from the
German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citizens of Germany, see also German nationality law * German language The German la ...

German
word meaning salt. Hallstatt was the site of the world's first
salt mine A salt mine is a mine from which salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crystallinity, crystalline mi ...
. The town gave its name to the
Hallstatt culture The Hallstatt culture was the predominant Western Western may refer to: Places *Western, Nebraska, a village in the US *Western, New York, a town in the US *Western Creek, Tasmania, a locality in Australia *Western Junction, Tasmania, a loc ...

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 A hand tool is any tool A tool is an object that can extend an individual's ability to modify features of the surrounding environment. Although many animals use simple to ...

pickaxe
s and
shovel Image:Unloading_flood_relief_supplies_at_Gilgit_Air_Base_2010-09-18_1.jpg, 260px, A man carrying shovels A shovel is a tool for digging, lifting, and moving bulk materials, such as soil, coal, gravel, snow, sand, or ore. Most shovels are hand too ...

shovel
s, began
open pan salt making Open-pan salt making is a method of salt production wherein salt is extracted from brine Brine is a high-concentration solution Image:SaltInWaterSolutionLiquid.jpg, Making a saline water solution by dissolving Salt, table salt (sodium chl ...
. During the first millennium BC, Celtic communities grew rich trading salt and
salted meat Image:Salt beef bagel.jpg, A bagel containing Corned beef, salt beef (corned beef) and Mustard (condiment), mustard Salt-cured meat or salted meat is meat or fish preserved or Curing (food preservation), cured with salt. Salting (food), Salting, ...
to
Ancient Greece Ancient Greece ( el, Ἑλλάς, Hellás) was a civilization belonging to a period of History of Greece, Greek history from the Greek Dark Ages of the 12th–9th centuries BC to the end of Classical Antiquity, antiquity ( AD 600). This era wa ...
and
Ancient Rome In historiography Historiography is the study of the methods of historian ( 484– 425 BC) was a Greek historian who lived in the 5th century BC and one of the earliest historians whose work survives. A historian is a person who stud ...
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 An employment contract or contract of employment is a kind of contract A contract is a legally binding agreement that def ...
'' comes from the
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, it became ...

Latin
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 The Roman army (: ) was the armed forces deployed by the Romans throughout the duration of , from the (to c. 500 BC) to the (500–31 BC) and the (31 BC– ...

Roman Legion
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, salad greens, pot herbs, vegetable greens, or simply greens, are plant eaten as a , sometimes accompanied by tender and s. Although they come from a very wide variety of plants, most share a great ...
s. Wars have been fought over salt.
Venice Venice ( ; it, Venezia ; vec, Venesia or ) is a city in northeastern Italy Italy ( it, Italia ), officially the Italian Republic ( it, Repubblica Italiana, links=no ), is a country consisting of delimited by the and surrounding ...
fought and won a war with
Genoa Genoa ( ; it, Genova ; locally ; lij, Zêna ; English, historically, and la, Genua) is the capital of the Regions of Italy, Italian region of Liguria and the List of cities in Italy, sixth-largest city in Italy. In 2015, 594,733 people lived ...
over the product, and it played an important part in the
American Revolution The American Revolution was an ideological and political revolution which occurred in colonial North America between 1765 and 1783. The Americans in the Thirteen Colonies The Thirteen Colonies, also known as the Thirteen British Colo ...
. 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 Debt is an obligation that requires one party, the debtor, to pay money or other agreed-upon value to anot ...
, and towns like
Liverpool Liverpool is a City status in the United Kingdom, city and metropolitan borough in Merseyside, England. With a population of in 2019, it is the List of English districts by population, tenth largest English district by population, and its ...

Liverpool
flourished on the export of salt extracted from the salt mines of
Cheshire Cheshire ( ;), archaically the County Palatine of Chester, is a historic and ceremonial county in northwest England North West England is one of nine official regions of England The regions, formerly known as the government office re ...

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, Cristóbal Colón * pt, Cristóvão Colombo * ca, Cristòfor (or ) * la, Christophorus Columbus. (; born between 25 August and 31 October 1451, died 20 May 1506) was an Italian ...

Christopher Columbus
are said to have been financed from salt production in southern Spain, and the oppressive salt tax in France was one of the causes of the
French Revolution The French Revolution ( ) was a period of radical political and societal change in France France (), officially the French Republic (french: link=no, République française), is a spanning and in the and the , and s. Its ...

French Revolution
. After being repealed, this tax was reimposed by
Napoleon Napoléon Bonaparte (15 August 1769 – 5 May 1821) was a French military and political leader. He rose to prominence during the French Revolution The French Revolution ( ) refers to the period that began with the Estates General o ...

Napoleon
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) was an Indian lawyer, anti-colonial nationalist Quote: "... marks Gandhi as a hybrid cosmopolitan figure who transformed ... anti-colonial nationalist politics in the ...

Mahatma Gandhi
led a crowd of 100,000 protestors on the "Dandi March" or "
Salt Satyagraha The Salt March, also known as the Salt Satyagraha, Dandi March and the Dandi Satyagraha, was an act of nonviolent civil disobedience in colonial India Colonial India was the part of the Indian subcontinent that was under the jurisdiction ...

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 Civil disobedience is the active, professed refusal of a citizen Citizenship is a relationship between an individual and a state to which the individual owes allegiance and in turn is entitled to its protection. Each state determines the co ...
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 rule in India The British Raj (; from ''rāj'', literally, "rule" in Sanskrit Sanskrit (, attributively , ''saṃskṛta-'', ...
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 salt (chemistry), salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With Molar mass, molar ...
(NaCl).
Sea salt Sea salt is salt 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 ...

Sea salt
and mined salt may contain
trace element __NOTOC__ A trace element, also called minor element, is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and beha ...
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 Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they under ...
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 The boiling point of a substance is the temperature at which the vapor pressure 280px, The ''pistol test tube'' experiment. The tube contains alcohol and is closed with a piece of cork. By heating the alcohol, the vapors fill in the space, inc ...
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 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 Sodium chloride , commonly known as salt (although sea salt also contains other chemical salt (chemistry), salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With Molar mass, molar ...
. Usually,
anticaking agentsAn anticaking agent is an additive Additive may refer to: Mathematics * Additive function In number theory, an additive function is an arithmetic function ''f''(''n'') of the positive integer ''n'' such that whenever ''a'' and ''b'' are coprime, ...
such as
sodium aluminosilicate Sodium aluminosilicate refers to compounds which contain sodium Sodium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pu ...
or
magnesium carbonate Magnesium carbonate, Mg CO3 (archaic name magnesia alba), is an inorganic salt that is a white solid. Several hydrate In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, com ...

magnesium carbonate
are added to make it free-flowing.
Iodized salt Iodised salt ( also spelled iodized salt) is table salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crystallin ...
, containing
potassium iodide Potassium iodide is a chemical compound, Pharmaceutical drug, medication, and dietary supplement. As a medication it is used to treat hyperthyroidism, in radiation emergencies, and to protect the thyroid gland when certain types of radiopharmac ...

potassium iodide
, is widely available. Some people put a
desiccant A desiccant is a hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal ...
, such as a few grains of uncooked
rice Rice is the seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was relea ...

rice
or a
saltine cracker A saltine or soda cracker is a thin, usually square cracker made from white flour, Baker's yeast, yeast, and baking soda, with most varieties lightly sprinkled with coarse salt. It has perforations over its surface, as well as a distinctively dry ...
, 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 Iodine is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical ele ...

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''. * Angular deficiency, in geometry, the difference between a sum of angles and the c ...
of the element can cause lowered production of
thyroxine File:Thyroid_system.svg, upright=1.5, The thyroid The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobe (anatomy), lobes. The lower two thirds of the lobes are conne ...

thyroxine
(
hypothyroidism Hypothyroidism (also called ''underactive thyroid'', ''low thyroid'' or ''hypothyreosis'') is a disorder of the endocrine system in which the thyroid gland The thyroid, or thyroid gland, is an endocrine gland in the neck consisting of two ...

hypothyroidism
) and enlargement of the thyroid gland (
endemic goitre Endemic goiter is a type of goitre A goitre, American and British English spelling differences#re er, or goiter, is a swelling in the neck resulting from an enlarged thyroid, thyroid gland. A goitre can be associated with a thyroid that is not funct ...
) in adults or
cretinism Congenital iodine deficiency syndrome (formerly known as cretinism) is a medical condition present at birth marked by impaired physical and mental development, due to insufficient thyroid hormone (hypothyroidism) often caused by insufficient dieta ...
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, Pharmaceutical drug, medication, and dietary supplement. As a medication it is used to treat hyperthyroidism, in radiation emergencies, and to protect the thyroid gland when certain types of radiopharmac ...

potassium iodide
,
sodium iodide Sodium iodide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as parenthe ...

sodium iodide
, or
sodium iodate Sodium iodate (Na I O3) is the sodium Sodium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting o ...
. A small amount of
dextrose Glucose is a simple sugar Sugar is the generic name for sweet-tasting, soluble carbohydrate is a disaccharide A disaccharide (also called a double sugar or ''biose'') is the sugar formed when two monosaccharides are joined by glyco ...

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 and formerly mental retardation (MR),Rosa's Law Rosa's Law is a United States The United States of America (USA), commonly known as the United States (U.S. or US), o ...
. 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 Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

United States
, the
Food and Drug Administration 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 Continental United States, primarily located in North America. It consists of 50 U.S. state, st ...
(FDA) recommends 150
micrograms In the metric system A metric system is a system of measurement A system of measurement is a collection of units of measurement and rules relating them to each other. Systems of measurement have historically been important, regulated and def ...
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 (chemistry), salt of the complex (chemistry), coordination compound of formula e(CN)6−. In its Hydrate, hydrous form, Na4Fe(CN)6 (sodium ferrocyanide decahydrate), it is sometimes known as yellow prussia ...

Sodium ferrocyanide
, also known as yellow prussiate of soda, is sometimes added to salt as an
anticaking agentAn anticaking agent is an additive Additive may refer to: Mathematics * Additive function In number theory, an additive function is an arithmetic function ''f''(''n'') of the positive integer ''n'' such that whenever ''a'' and ''b'' are coprime, ...
. Such anticaking agents have been added since at least 1911 when
magnesium carbonate Magnesium carbonate, Mg CO3 (archaic name magnesia alba), is an inorganic salt that is a white solid. Several hydrate In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, com ...

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 ToxicityThe Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment (COT) is a United Kingdom, UK independent scientific committee that provides advice to the Food Standards Agency, the Department of Health (United Kingdom), Departm ...
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 Calcium is a chemical element with the Symbol (chemistry), symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride la ...

tricalcium phosphate
,
calcium Calcium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elem ...

calcium
or magnesium carbonates,
fatty acid In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during ...
salts (
acid salt Acid salts are a class of salts In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and ...
s),
magnesium oxide Magnesium oxide ( Mg O), or magnesia, is a white hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environme ...

magnesium oxide
,
silicon dioxide Silicon dioxide, also known as silica, is an oxide of rutile. Ti(IV) centers are grey; oxygen centers are red. Notice that oxygen forms three bonds to titanium and titanium forms six bonds to oxygen. An oxide () is a chemical compound that con ...
,
calcium silicate Calcium silicate is the chemical compound Ca2SiO4, also known as calcium orthosilicate and is sometimes formulated as 2CaO·SiO2. It is also referred to by the shortened trade name Cal-Sil or Calsil. It occurs naturally as the mineral larnite. ...
, sodium aluminosilicate and
calcium aluminosilicate Calcium aluminosilicate, an aluminosilicate compound with calcium Calcium is a chemical element with the Symbol (chemistry), symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitr ...
. Both the European Union and the United States Food and Drug Administration permitted the use of
aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity towards , and of on the surface when exposed to air ...

aluminium
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 Anemia ( also spelled anaemia) is a decrease in the total amount of red blood cells (RBCs) or hemoglobin in the blood, or a lowered ability of the blood to carry oxygen Oxygen is the chemical element ...
, 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 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 fluoride 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 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 ...

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. Salts have diverse 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 distinctive flavour varying with its source. 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 Cooling is removal of heat, usually resulting in a lower temperature and/or phase change. Temperature lowering achieved by any other means may also be called cooling.ASHRAE Terminology, https://www.ashrae.org/ ...

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 redox, oxidation of fats that cause Ran ...

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 extensively in cooking as a flavoring, and cooking techniques such as with salt crusts and brining. 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 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 Chronic condition, long-term Disease, medical condition in which the blood pressure in the artery, arteries is persistently elevated. High blood pressure usually does not ...

hypertension
. The
World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations United Nations Specialized Agencies are autonomous organizations working with the United Nations and each other through the co-ordinating machinery of the Unit ...
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 and
chlorine Chlorine is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemica ...

chlorine
. These are used in the manufacture of PVC,
paper pulp Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fiber Cellulose fibers () are fibers made with ethers or esters of cellulose, which can be obtained from the bark, wood or leaves of plants, ...
and many other inorganic and organic compounds. Salt is also used as a Flux (metallurgy), flux in the production of
aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity towards , and of on the surface when exposed to air ...

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 used to Saponification, saponify fats. 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
canning Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container (jar A jar is a rigid, cylindrical or slightly conical container, typically made of , , or , with a wide mouth or op ...

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 kilogram The kilogram (also kilogramme) is the base unit of mass Mass is the physical quantity, quantity of ''matter'' in a physical body. It is also a meas ...
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 Salinity () is the saltiness or amount of dissolved in a body of , called (see also ). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal to ‰). Salinity is an important ...

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 sources are either salt mine, 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 Open pan salt making, shallow open pans that were heated to accelerate evaporation. Vacuum-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, 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 Shechem , also spelled Sichem (; he, שְׁכָם / Standard ''Šəḵem'' Tiberian ''Šeḵem'', "shoulder"; grc, Συχέμ LXX), was a Canaan A 1692 map of Canaan, by Philip Lea Canaan (; Northwest Semitic: ; Phoenician lang ...

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

;Books * * * * * * * * {{Good article Edible salt, Food additives Sodium minerals Objects believed to protect from evil Food powders