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111-478: Sodium chloride / ˌ s oʊ d i ə m ˈ k l ɔːr aɪ d / , commonly known as edible salt , is an ionic compound with the chemical formula NaCl , representing a 1:1 ratio of sodium and chlorine ions. It is transparent or translucent, brittle, hygroscopic , and occurs as the mineral halite . In its edible form, it is commonly used as a condiment and food preservative . Large quantities of sodium chloride are used in many industrial processes, and it

222-625: A Bresle test . Salinization (increasing salinity, aka freshwater salinization syndrome ) and subsequent increased metal leaching is an ongoing problem throughout North America and European fresh waterways. In highway de-icing, salt has been associated with corrosion of bridge decks, motor vehicles, reinforcement bar and wire, and unprotected steel structures used in road construction. Surface runoff , vehicle spraying, and windblown salt also affect soil, roadside vegetation, and local surface water and groundwater supplies. Although evidence of environmental loading of salt has been found during peak usage,

333-432: A face-centered cubic (fcc) lattice with a two-atom basis or as two interpenetrating face centered cubic lattices. The first atom is located at each lattice point, and the second atom is located halfway between lattice points along the fcc unit cell edge. Solid sodium chloride has a melting point of 801 °C and liquid sodium chloride boils at 1465 °C. Atomic-resolution real-time video imaging allows visualization of

444-490: A 7 mm neoprene wet suit offers much less exposure protection under 100 feet of water than at the surface. A recent advance in neoprene for wet suits is the "super-flex" variety, which uses spandex in the knit liner fabric for greater flexibility and stretch. A drysuit is similar to a wetsuit, but uses thicker and more durable neoprene to create an entirely waterproof suit that is suitable for wear in extremely cold water or polluted water. Recently, neoprene has become

555-423: A base for adhesives , noise isolation in power transformer installations, and as padding in external metal cases to protect the contents while allowing a snug fit. It resists burning better than exclusively hydrocarbon based rubbers, resulting in its appearance in weather stripping for fire doors and in combat related attire such as gloves and face masks. Because of its tolerance of extreme conditions, neoprene

666-598: A favorite material for lifestyle and other home accessories including laptop sleeves, tablet holders, remote controls , mouse pads , and cycling chamois. The Rhodes piano used hammer tips made of neoprene in its electric pianos, after changing from felt hammers around 1970. Neoprene is also used for speaker cones and drum practice pads. Hydroponic and aerated gardening systems make use of small neoprene inserts to hold plants in place while propagating cuttings or using net cups. Inserts are relatively small, ranging in size from 1.5 to 5 inches (4 to 13 cm). Neoprene

777-438: A fertilizer, applying a moderate concentration helps avoid potential toxicity; typically, 1–3 grams (0.035–0.106 oz) per liter is considered safe and effective for most plants. Sodium chloride is one of the largest volume inorganic raw materials. It is a feedstock in the production of caustic soda and chlorine . These are used in the manufacture of PVC , paper pulp and many other inorganic and organic compounds. Salt

888-443: 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. Only a small percentage of the salt manufactured in the world is used in food. The remainder is used in agriculture, water treatment, chemical production, de-icing, and other industrial use cases. In the practice of watering plants with salt as

999-422: 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. 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 proteolyzed forms of epithelial sodium channel (ENaC) function as the human salt taste receptor. Table salt

1110-632: A major source of food spoilage. Even though more effective desiccants are available, few are safe for humans to ingest. Many microorganisms cannot live in a salty environment: water is drawn out of their cells by osmosis . For this reason salt is used to preserve some foods, such as bacon, fish, or cabbage. In many dairy industries, salt is added to cheese as a color-, fermentation-, and texture-control agent. The dairy subsector includes companies that manufacture creamery butter, condensed and evaporated milk, frozen desserts, ice cream, natural and processed cheese, and specialty dairy products. In canning, salt

1221-580: A marketing strategy that included publishing its own technical journal, which extensively publicized neoprene's uses as well as advertising other companies' neoprene-based products. By 1939, sales of neoprene were generating profits over $ 300,000 for the company (equivalent to $ 6,600,000 in 2023). The high tensile performance of neoprene is a result of its highly regular backbone structure, which causes neoprene to undergo strain crystallization under tensile loading. A two parameter (strain rate and temperature) hyperelastic model can accurately capture much of

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1332-522: A metaphor. Uses include the tale of how Lot's wife is turned into a pillar of salt when looking back at the cities of Sodom and Gomorrah as they are destroyed. In the New Testament , Jesus refers to his followers as the " salt of the earth ". In Aztec mythology, Huixtocihuatl was a fertility goddess who presided over salt and salt water. Salt is an auspicious substance in Hinduism and

1443-461: 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 flavour than pure sodium chloride when sprinkled on top of food. When salt is added during cooking however, these flavours would likely be overwhelmed by those of

1554-438: A neoprene- spandex mixture for manufacture of wheelchair positioning harnesses. In tabletop wargames, neoprene mats printed with grassy, sandy, icy, or other natural features have become popular gaming surfaces. They are durable, firm and stable, and attractive in appearance, and also favoured for their ability to roll up in storage but lie flat when unrolled. Because of its chemical resistance and overall durability, neoprene

1665-460: A preservative, salt inhibits the growth of bacteria. Salt acts as a binder in sausages to form a binding gel made up of meat, fat, and moisture. Salt also acts as a flavor enhancer and as a tenderizer . It is used as a cheap and safe desiccant because of its hygroscopic properties, making salting an effective method of food preservation historically; the salt draws water out of bacteria through osmotic pressure , keeping it from reproducing,

1776-453: A problem in any coating application, because trapped salts cause great problems in adhesion. Naval authorities and ship builders monitor the salt concentrations on surfaces during construction. Maximal salt concentrations on surfaces are dependent on the authority and application. The IMO regulation is mostly used and sets salt levels to a maximum of 50 mg/m soluble salts measured as sodium chloride. These measurements are done by means of

1887-535: A salt spring in Lunca , Neamț County , Romania. Evidence indicates that Neolithic people of the Precucuteni Culture were boiling the salt-laden spring water through the process of briquetage to extract salt as far back as 6050 BC. The salt extracted from this operation may have directly correlated with the rapid growth of this society's population soon after production began. The harvest of salt from

1998-514: 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. Salt plays a role within different Christian traditions. It

2109-426: A scrubbing agent when combined with oil. 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 , pickled foods , and snack foods or other convenience foods ), where it functions as both a preservative and a flavouring . Dairy salt

2220-934: A sodium chloride solution remains ≈7 due to the extremely weak basicity of the Cl ion, which is the conjugate base of the strong acid HCl. In other words, NaCl has no effect on system pH in diluted solutions where the effects of ionic strength and activity coefficients are negligible. Common salt has a 1:1 molar ratio of sodium and chlorine. In 2013, compounds of sodium and chloride of different stoichiometries have been discovered; five new compounds were predicted (e.g., Na 3 Cl, Na 2 Cl, Na 3 Cl 2 , NaCl 3 , and NaCl 7 ). The existence of some of them has been experimentally confirmed at high pressures and other conditions: cubic and orthorhombic NaCl 3 , two-dimensional metallic tetragonal Na 3 Cl and exotic hexagonal NaCl. This indicates that compounds violating chemical intuition are possible, in simple systems under non-ambient conditions. Salt

2331-505: 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. Away from

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2442-439: A yellow colour. 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

2553-458: Is a good choice for supporting plants because of its flexibility and softness, allowing plants to be held securely in place without the chance of causing damage to the stem. Neoprene root covers also help block out light from entering the rooting chamber of hydroponic systems, allowing for better root growth and helping to deter the growth of algae. During the COVID-19 global pandemic, neoprene

2664-434: Is a major source of sodium and chlorine compounds used as feedstocks for further chemical syntheses . Another major application of sodium chloride is deicing of roadways in sub-freezing weather. In addition to the many familiar domestic uses of salt, more dominant applications of the approximately 250 million tonnes per year production (2008 data) include chemicals and de-icing. Salt is used, directly or indirectly, in

2775-417: Is a popular material in making protective clothing for aquatic activities. Foamed neoprene is commonly used to make fly fishing waders, wetsuits , and drysuits as it provides excellent insulation against cold. The foam is quite buoyant, and divers compensate for this by wearing weights. Since foam neoprene contains gas pockets, the material compresses under water pressure, getting thinner at greater depths;

2886-417: Is a result of the competing factors of scission of the main polymer chain and oxidative cross-linking. Chain scission leads to degradation, embrittlement , and a loss of toughness. Oxidation reactions in the presence of heating leads to increased cross-linking, which in turn causes hardening. The interplay of both these factors determines the resulting effect on material mechanical properties; cross-linking

2997-695: 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

3108-467: Is added to food, either by the food producer or by the consumer, as a flavor enhancer, preservative, binder, fermentation -control additive, texture-control agent, and color developer. The salt consumption in the food industry is subdivided, in descending order of consumption, into other food processing, meat packers, canning , baking, dairy, and grain mill products. Salt is added to promote color development in bacon, ham and other processed meat products. As

3219-530: Is added to secure the soil and to provide firmness to the foundation on which highways are built. The salt acts to minimize the effects of shifting caused in the subsurface by changes in humidity and traffic load. Hard water contains calcium and magnesium ions that interfere with action of soap and contribute to the buildup of a scale or film of alkaline mineral deposits in household and industrial equipment and pipes. Commercial and residential water-softening units use ion-exchange resins to remove ions that cause

3330-483: Is also a major source. China is the world's main supplier of salt. In 2017, world production was estimated at 280 million tonnes , the top five producers (in million tonnes) being China (68.0), United States (43.0), India (26.0), Germany (13.0), and Canada (13.0). Salt is also a byproduct of potassium mining. Salt#Edible salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it

3441-476: Is also used a seasoning agent, e.g. in potato chips, pretzels , and cat and dog food. Sodium chloride is used in veterinary medicine as emesis -causing agent. It is given as warm saturated solution. Emesis can also be caused by pharyngeal placement of small amount of plain salt or salt crystals. For watering plants to use sodium chloride ( NaCl ) as a fertilizer, moderate concentration is used to avoid potential toxicity: 1–3 grams (0.035–0.106 oz) per liter

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3552-447: Is an important component of drilling fluids in well drilling. It is used to flocculate and increase the density of the drilling fluid to overcome high downwell gas pressures. Whenever a drill hits a salt formation, salt is added to the drilling fluid to saturate the solution in order to minimize the dissolution within the salt stratum. Salt is also used to increase the curing of concrete in cemented casings. In textiles and dyeing, salt

3663-469: Is an important micronutrient for humans, and a deficiency of the element can cause lowered production of thyroxine ( hypothyroidism ) and enlargement of the thyroid gland ( endemic goitre ) in adults or cretinism in children. Iodized salt has been used to correct these conditions since 1924 and consists of table salt mixed with a minute amount of potassium iodide , sodium iodide , or sodium iodate . A small amount of dextrose may be added to stabilize

3774-561: 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 recommends that adults should consume less than 2,000 mg of sodium (which

3885-420: Is contained in 5   g 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

3996-419: 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.The mine is also a major tourist attraction, receiving around a quarter of a million visitors a year. Salt has long held an important place in religion and culture. At

4107-693: Is either beneficial or harmful. Evidence shows a more complicated relationship between salt and cardiovascular disease. "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

4218-484: Is found in the Earth's crust as the mineral halite (rock salt), and a tiny amount exists as suspended sea salt particles in the atmosphere. These particles are the dominant cloud condensation nuclei far out at sea, which allow the formation of clouds in otherwise non-polluted air . Salt is currently mass-produced by evaporation of seawater or brine from brine wells and salt lakes . Mining of rock salt

4329-574: Is generally safe and effective for most plants. Sodium chloride is used together with water as one of the primary solutions for intravenous therapy . Nasal spray often contains a saline solution. Sodium chloride is also available as an oral tablet, and is taken to treat low sodium levels. Sodium chloride is the principal extinguishing agent in dry-powder fire extinguishers that are used on combustible metal fires, for metals such as magnesium, zirconium, titanium, and lithium (Class D extinguishers). The salt forms an oxygen-excluding crust that smothers

4440-539: Is made up of just under 40% sodium by weight, so a 6   g serving (1   teaspoon) contains about 2,400   mg 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 ). Most of the sodium in the Western diet comes from salt. The habitual salt intake in many Western countries

4551-606: Is mandatory in the rite of the Tridentine Mass . 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, and it is permitted to be added to the water "where it is customary" in the Roman Catholic rite of Holy water. The Bible makes multiple mentions of salt , both of the mineral itself and as

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4662-439: Is manufactured by foaming the rubber with nitrogen gas, where the tiny enclosed and separated gas bubbles can also serve as insulation. Nitrogen gas is most commonly used for the foaming of neoprene foam due to its inertness, flame resistance, and large range of processing temperatures. Neoprene is used as a component of elastomeric bridge bearings , to support heavy loads while permitting small horizontal movements. Neoprene

4773-547: 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 . Unrefined sea salt contains small amounts of magnesium and calcium halides and sulfates , 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 (i.e., it gradually absorbs moisture from air if stored uncovered). Algal products contribute

4884-401: Is more formally called table salt . In the form of a natural crystalline mineral, salt is also known as rock salt or halite . Salt is essential for life in general (being the source of the essential dietary minerals sodium and chlorine ), and saltiness is one of the basic human tastes . Salt is one of the oldest and most ubiquitous food seasonings , and is known to uniformly improve

4995-409: Is mostly sodium chloride (NaCl). Sea salt and mined salt may contain trace elements . 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

5106-435: Is of interest in the devulcanization process Finally, ultraviolet radiation is seen to decrease the mechanical properties of neoprene, which is important for outdoors applications of neoprene. Neoprene resists degradation more than natural or synthetic rubber . This relative inertness makes neoprene well suited for demanding applications such as gaskets , hoses , and corrosion -resistant coatings . It can be used as

5217-422: Is prepared by free radical emulsion polymerization . Polymerization is initiated using potassium persulfate . Bifunctional nucleophiles, metal oxides (e.g. zinc oxide), and thioureas are used to crosslink individual polymer strands. Neoprene was invented by DuPont scientists on April 17, 1930, after Elmer K. Bolton of DuPont attended a lecture by Fr Julius Arthur Nieuwland , a professor of chemistry at

5328-428: 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 anticlastogenic and antimutagenic properties of doenjang (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 bread or pretzel making, and as

5439-586: Is primarily added as a flavor enhancer and preservative . It also is used as a carrier for other ingredients, dehydrating agent, enzyme inhibitor and tenderizer. In baking, salt is added to control the rate of fermentation in bread dough. It also is used to strengthen the gluten (the elastic protein-water complex in certain doughs) and as a flavor enhancer, such as a topping on baked goods. The food-processing category also contains grain mill products. These products consist of milling flour and rice and manufacturing cereal breakfast food and blended or prepared flour. Salt

5550-435: Is recommended by developed countries, one review recommended that sodium intake be reduced to at least 1,200 mg (contained in 3   g of salt) per day, as a further reduction in salt intake led to a greater 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

5661-556: 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 , an indigenous group from the Paraguayan Chaco , obtain their salt from

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5772-524: Is sometimes used in the manufacture of dishwashing gloves, especially as an alternative to latex . In fashion, neoprene has been used by designers such as Gareth Pugh , Balenciaga , Rick Owens , Lanvin , and Vera Wang . Neoprene was also used as an experimental fabric to upholster a mirror by designer Flavia Brilli for her mirror brand Jazz Frames . Some people are allergic to neoprene while others can get dermatitis from thiourea residues left from its production. The most common accelerator in

5883-560: Is then reacted with sulfuric acid and a reducing agent such as methanol to manufacture chlorine dioxide , a bleaching chemical that is widely used to bleach wood pulp . In tanning and leather treatment, salt is added to animal hides to inhibit microbial activity on the underside of the hides and to attract moisture back into the hides. In rubber manufacture, salt is used to make buna , neoprene , and white rubber types. Salt brine and sulfuric acid are used to coagulate an emulsified latex made from chlorinated butadiene . Salt also

5994-503: Is thought to dominate for neoprene. As neoprene is used to make electric cable jackets in nuclear power plants, the effect of gamma radiation on the mechanical properties of neoprene has also been investigated. Chain scission, possibly triggered by free radicals from irradiated oxygen, is seen to deteriorate the mechanical properties of neoprene. Likewise, the tensile strength, hardness, and ultimate elongation of neoprene can also be degraded upon exposure to microwave radiation , which

6105-409: Is used as a flux in the production of aluminium . For this purpose, a layer of melted salt floats on top of the molten metal and removes iron and other metal contaminants. It is used in the manufacture of soaps and glycerine , 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 , when salt added to

6216-426: Is used as a brine rinse to separate organic contaminants, to promote "salting out" of dyestuff precipitates, and to blend with concentrated dyes to increase yield in dyebaths and make the colors look sharper. One of its main roles is to provide the positive ion charge to promote the absorption of negatively charged ions of dyes. For use in the pulp and paper industry , it is used to manufacture sodium chlorate , which

6327-461: Is used extensively in cooking as a flavouring, and in cooking techniques such as with salt crusts and brining . The main sources of salt in the Western diet, apart from direct use, are bread and cereals, meat, 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

6438-468: Is used in 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 Buddhist tradition, and when returning home from a funeral , a pinch of salt is thrown over

6549-441: Is used in many cuisines, and it is often found in salt shakers on diners' eating tables for their personal use on food. Salt is also an ingredient in many manufactured foodstuffs. Table salt is a refined salt containing about 97 to 99 percent sodium chloride . Usually, anticaking agents such as sodium aluminosilicate or magnesium carbonate are added to make it free-flowing. Iodized salt , containing potassium iodide ,

6660-477: Is used in religious ceremonies and has other cultural and traditional significance. Salt is processed from salt mines , and by the evaporation of seawater ( sea salt ) and mineral-rich spring water in shallow pools. The greatest single use for salt (sodium chloride) is as a feedstock for the production of chemicals. It is used to produce caustic soda and chlorine , and in the manufacture of products such as polyvinyl chloride , plastics , and paper pulp . Of

6771-578: Is used in the Solvay process to produce sodium carbonate and calcium chloride . Sodium carbonate, in turn, is used to produce glass , sodium bicarbonate , and dyes , as well as a myriad of other chemicals. In the Mannheim process , sodium chloride is used for the production of sodium sulfate and hydrochloric acid . Sodium chloride is heavily used, so even relatively minor applications can consume massive quantities. In oil and gas exploration, salt

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6882-617: Is used in the preparation of butter and cheese products. As a flavouring, 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 , salting was one of the main methods of 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

6993-448: Is used to line landfills. Neoprene's burn point is around 260 °C (500 °F). In its native state, neoprene is a very pliable rubber-like material with insulating properties similar to rubber or other solid plastics. Neoprene foam is used in many applications and is produced in either closed-cell or open-cell form. The closed-cell form is waterproof , less compressible and more expensive. The open-cell form can be breathable . It

7104-434: Is widely available. Some people put a desiccant , such as a few grains of uncooked rice or a saltine cracker , in their salt shakers to absorb extra moisture and help break up salt clumps that may otherwise form. 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

7215-590: The Committee on Toxicity in 1988. Other anticaking agents sometimes used include tricalcium phosphate , calcium or magnesium carbonates, fatty acid salts ( acid salts ), magnesium oxide , silicon dioxide , calcium silicate , sodium aluminosilicate and calcium aluminosilicate . Both the European Union and the United States Food and Drug Administration permitted the use of aluminium in

7326-622: The German word Salz , salt. Hallstatt was the site of the world's first salt mine . The town gave its name to the Hallstatt culture that began mining for salt in the area in about 800 BC. Around 400 BC, the townsfolk, who had previously used pickaxes and shovels , began open pan salt making . During the first millennium BC, Celtic communities grew rich trading salt and salted meat to Ancient Greece and Ancient Rome in exchange for wine and other luxuries. The word salary comes from

7437-692: The Latin word for salt. The reason for this is unknown; a persistent modern claim that the Roman Legions were sometimes paid in salt is baseless. The word salad literally means "salted", and comes from the ancient Roman practice of salting leaf vegetables . Wars have been fought over salt. Venice won a war with Genoa over the product, and it played a role in the American Revolution . Cities on overland trade routes grew rich by levying duties , and towns like Liverpool flourished on

7548-722: The University of Notre Dame . Nieuwland's research was focused on acetylene chemistry and during the course of his work he produced divinyl acetylene, a jelly that firms into an elastic compound similar to rubber when passed over sulfur dichloride . After DuPont purchased the patent rights from the university, Wallace Carothers of DuPont took over commercial development of Nieuwland's discovery in collaboration with Nieuwland himself and DuPont chemists Arnold Collins , Ira Williams and James Kirby. Collins focused on monovinyl acetylene and allowed it to react with hydrogen chloride gas, manufacturing chloroprene . DuPont first marketed

7659-413: The dihydrate NaCl·2H 2 O. Solutions of sodium chloride have very different properties from those of pure water; the freezing point is −21.12 °C (−6.02 °F) for 23.31 wt% of salt, and the boiling point of saturated salt solution is around 108.7 °C (227.7 °F). Salt is essential to the health of humans and other animals, and it is one of the five basic taste sensations . Salt

7770-826: The obsidian trade in Anatolia in the Neolithic Era . Salt was included among funeral offerings found in ancient Egyptian tombs from the third millennium BC, as were salted birds, and salt fish. From about 2800 BC, the Egyptians began exporting salt fish to the Phoenicians in return for Lebanon cedar , glass, and the dye Tyrian purple ; the Phoenicians traded Egyptian salted fish and salt from North Africa throughout their Mediterranean trade empire. Herodotus described salt trading routes across Libya back in

7881-454: The tanning of hides, the preservation of meat and fish and the canning of meat and vegetables. 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 tonnes , the top six producers being China (68 million),

7992-665: 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 Tuareg have traditionally maintained routes across the Sahara especially for the transportation of salt by Azalai (salt caravans). The caravans still cross

8103-460: The UK the recommended iodine content of iodized salt is 10–22 ppm. Sodium ferrocyanide , yellow prussiate 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

8214-490: 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 35 g (1.2 oz) of dissolved salts , predominantly sodium ( Na ) and chloride ( Cl ) ions , per kilogram (2.2 lbs) of water. The world's oceans are

8325-429: The annual global production of around three hundred million tonnes , only a small percentage is used for human consumption. Other uses include water conditioning processes, de-icing highways, and agricultural use. Edible salt is sold in forms such as sea salt and table salt, the latter of which usually contains an anti-caking agent and may be iodised to prevent iodine deficiency . As well as its use in cooking and at

8436-692: The ash produced by burning the timber of the Indian salt tree ( Maytenus vitis-idaea ) and other trees. The largest mine operated by underground workings in the world is the Sifto mine, located mostly 550 meters below Lake Huron, in Goderich, Ontario (Canada). About seven million tons of salt are extracted from it annually. The Khewra Salt Mine in Pakistan has nineteen storeys, eleven of which are underground, and 400 km (250 mi) of passages. The salt

8547-671: The availability of salt has been pivotal to civilization. What is now thought to have been the first city in Europe is Solnitsata , in Bulgaria , which was a salt mine, providing the area now known as the Balkans with salt since 5400 BC. Salt was 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

8658-400: The coast natives lost their previous profits; as of the late 1950s, sea salt was still the currency best appreciated in the interior. Salzburg , Hallstatt , and Hallein lie within 17 km (11 mi) of each other on the river Salzach in central Austria in an area with extensive salt deposits. Salzach means "salt river" while Salzburg means "salt castle", both taking their names from

8769-413: The compound in 1931 under the trade name DuPrene, but its commercial possibilities were limited by the original manufacturing process, which left the product with a foul odor. A new process was developed, which eliminated the odor-causing byproducts and halved production costs, and the company began selling the material to manufacturers of finished end-products. To prevent shoddy manufacturers from harming

8880-444: The desert from southern Niger to Bilma , although much of the trade now takes place by truck. Each camel takes two bales of fodder and two of trade goods northwards and returns laden with salt pillars and dates. In Gabon, before the arrival of Europeans, the coast people carried on a remunerative trade with those of the interior by the medium of sea salt. This was gradually displaced by the salt that Europeans brought in sacks, so that

8991-581: The export of salt extracted from the salt mines of Cheshire . Various governments have at different times imposed salt taxes on their peoples. The voyages of Christopher Columbus are said to have been financed from salt production in southern Spain, and the oppressive salt tax in France was one of the causes of the French Revolution . After being repealed, this tax was reimposed by Napoleon when he became emperor to pay for his foreign wars , and

9102-598: The fire. Since at least medieval times, people have used salt as a cleansing agent rubbed on household surfaces. It is also used in many brands of shampoo , toothpaste, and popularly to de-ice driveways and patches of ice. Sodium chloride crystals have a transmittance of at least 90% (through 1 mm) for infrared light having wavelengths in the range 0.2– 18  μm . They were used in optical components such as windows and lenses, where few non-absorbing alternatives existed in that spectral range. While inexpensive, NaCl crystals are soft and hygroscopic – when exposed to

9213-478: 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 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 " bamboo salt "

9324-496: The formula [Na(H 2 O) 8 ], with the Na–O distance of 250  pm . The chloride ions are also strongly solvated, each being surrounded by an average of six molecules of water. Solutions of sodium chloride have very different properties from pure water. The eutectic point is −21.12 °C (−6.02 °F) for 23.31% mass fraction of salt, and the boiling point of saturated salt solution is near 108.7 °C (227.7 °F). The pH of

9435-435: 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 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

9546-447: The gritting vehicles despite being stockpiled prior to use. In recent years this additive has also been used in table salt. Other additives had been used in road salt to reduce the total costs. For example, in the US, a byproduct carbohydrate solution from sugar-beet processing was mixed with rock salt and adhered to road surfaces about 40% better than loose rock salt alone. Because it stayed on

9657-427: The hardness. These resins are generated and regenerated using sodium chloride. The second major application of salt is for deicing and anti-icing of roads, both in grit bins and spread by winter service vehicles . In anticipation of snowfall, roads are optimally "anti-iced" with brine (concentrated solution of salt in water), which prevents bonding between the snow-ice and the road surface. This procedure obviates

9768-690: The heavy use of salt after the snowfall. For de-icing, mixtures of brine and salt are used, sometimes with additional agents such as calcium chloride and/or magnesium chloride . The use of salt or brine becomes ineffective below −10 °C (14 °F). Salt for de-icing in the United Kingdom predominantly comes from a single mine in Winsford in Cheshire . Prior to distribution it is mixed with <100 ppm of sodium ferrocyanide as an anticaking agent , which enables rock salt to flow freely out of

9879-468: The initial stage of crystal nucleation of sodium chloride. The Thermal conductivity of sodium chloride as a function of temperature has a maximum of 2.03 W/(cm K) at 8 K (−265.15 °C; −445.27 °F) and decreases to 0.069 at 314 K (41 °C; 106 °F). It also decreases with doping . From cold (sub-freezing) solutions, salt crystallises with water of hydration as hydrohalite (the dihydrate NaCl·2 H 2 O ). In 2023, it

9990-651: The iodine. Iodine deficiency affects about two billion people around the world and is the leading preventable cause of intellectual disabilities . 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 Food and Drug Administration (FDA) recommends 150 micrograms of iodine per day for both men and women. US iodized salt contains 46–77 ppm (parts per million), whereas in

10101-412: The latter two compounds. In "doubly fortified salt", both iodide and iron salts are added. The latter alleviates iron deficiency anaemia , which interferes with the mental development of an estimated 40% of infants in the developing world. A typical iron source is ferrous fumarate . Another additive, especially important for pregnant women, is folic acid (vitamin B 9 ), which gives the table salt

10212-442: The left shoulder as this prevents evil spirits from entering the house. In Shinto , Shio ( 塩 , lit. "salt" ) is used for ritual purification of locations and people ( harae , specifically shubatsu ), and small piles of salt are placed in dishes by entrances to wardi off evil and to attract patrons. Neoprene Neoprene is produced by free-radical polymerization of chloroprene . In commercial production, this polymer

10323-411: The mechanical response of neoprene. Exposure to acetone and heat have been shown to degrade the tensile strength and ultimate elongation of neoprene, likely due to a loss of plasticizers as well as an increase in crosslinking during heat exposure. The response of neoprene to thermal aging depends not just on the highest temperature it is exposed to, but also on the exact temperature-time profile; this

10434-446: The product's reputation, the trademark DuPrene was restricted to apply only to the material sold by DuPont. Since the company itself did not manufacture any DuPrene-containing end products, the trademark was dropped in 1937 and replaced with a generic name, neoprene, in an attempt "to signify that the material is an ingredient, not a finished consumer product". DuPont then worked extensively to generate demand for its product, implementing

10545-408: The production of many chemicals, which consume most of the world's production. It is the starting point for the chloralkali process , the industrial process to produce chlorine and sodium hydroxide , according to the chemical equation This electrolysis is conducted in either a mercury cell, a diaphragm cell, or a membrane cell. Each of those uses a different method to separate the chlorine from

10656-582: The road longer, the treatment did not have to be repeated several times, saving time and money. In the technical terms of physical chemistry, the minimum freezing point of a water-salt mixture is −21.12 °C (−6.02 °F) for 23.31 wt% of salt. Freezing near this concentration is however so slow that the eutectic point of −22.4 °C (−8.3 °F) can be reached with about 25 wt% of salt. Road salt ends up in fresh-water bodies and could harm aquatic plants and animals by disrupting their osmoregulation ability. The omnipresence of salt in coastal areas poses

10767-503: The sea, 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 -based methods are also employed. The raw salt

10878-440: The sodium hydroxide. Other technologies are under development due to the high energy consumption of the electrolysis, whereby small improvements in the efficiency can have large economic paybacks. Some applications of chlorine include PVC thermoplastics production, disinfectants, and solvents. Sodium hydroxide is extensively used in many different industries enabling production of paper, soap, and aluminium etc. Sodium chloride

10989-727: 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 seal an agreement ceremonially, 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

11100-515: The spring rains and thaws usually dilute the concentrations of sodium in the area where salt was applied. A 2009 study found that approximately 70% of the road salt being applied in the Minneapolis-St Paul metro area is retained in the local watershed. Some agencies are substituting beer , molasses , and beet juice instead of road salt. Airlines utilize more glycol and sugar rather than salt-based solutions for deicing . Salt

11211-491: The surface of Xiechi Lake near Yuncheng in Shanxi , China, dates back to at least 6000 BC, making it one of the oldest verifiable saltworks. There is more salt in animal tissues, such as meat, blood, and milk, than in plant tissues. Nomads who subsist on their flocks and herds do not eat salt with their food, but agriculturalists, feeding mainly on cereals and vegetable matter, need to supplement their diet with salt. With

11322-623: The table, salt is present in many processed foods. Sodium is an essential element for human health via its role as an electrolyte and osmotic solute . However, excessive salt consumption increases the risk of cardiovascular diseases such as hypertension . Such health effects of salt have long been studied. Accordingly, numerous world health associations and experts in developed countries recommend reducing consumption of popular salty foods. The World Health Organization recommends that adults consume less than 2,000 mg of sodium, equivalent to 5 grams of salt, per day. All through history,

11433-455: The taste perception of food, including otherwise unpalatable food. Salting , brining , and pickling are ancient and important methods of food preservation . Some of the earliest evidence of salt processing dates to around 6000 BC, when people living in the area of present-day Romania boiled spring water to extract salts; a salt works in China dates to approximately the same period. Salt

11544-538: The time of Brahmanic sacrifices, in Hittite rituals and during festivals held by 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 Judaism , it is recommended to have either

11655-465: The vertices of a regular octahedron . In the language of close-packing , the larger chloride ions (167 pm in size) are arranged in a cubic array whereas the smaller sodium ions (116 pm) fill all the cubic gaps (octahedral voids) between them. This same basic structure is found in many other compounds and is commonly known as the NaCl structure or rock salt crystal structure. It can be represented as

11766-487: The water in ambient air, they gradually cover with "frost". This limits application of NaCl to dry environments, vacuum-sealed areas, or short-term uses such as prototyping. Materials that are mechanically stronger and less sensitive to moisture, such as zinc selenide and chalcogenide glasses , more widely used than NaCl. In solid sodium chloride, each ion is surrounded by six ions of the opposite charge as expected on electrostatic grounds. The surrounding ions are located at

11877-555: Was salting the earth : scattering salt around in a defeated city to prevent plant growth. The Bible tells the story of King Abimelech who was ordered by God to do this at Shechem , and various texts claim that the Roman general Scipio Aemilianus Africanus ploughed over and sowed the city of Carthage with salt after it was defeated in the Third Punic War (146 BC). Salt may have been used for barter in connection with

11988-482: Was discovered that under pressure, sodium chloride can form the hydrates NaCl·8.5H 2 O and NaCl·13H 2 O. The attraction between the Na and Cl ions in the solid is so strong that only highly polar solvents like water dissolve NaCl well. When dissolved in water, the sodium chloride framework disintegrates as the Na and Cl ions become surrounded by polar water molecules. These solutions consist of metal aquo complex with

12099-493: Was identified by some health experts as an effective material to use for home made face masks. Some commercial face mask manufacturers that use neoprene have claimed 99.9% filtration for particles as small as 0.1 microns. The size of coronavirus is identified to be on average 0.125 microns. Neoprene is used for Halloween masks and masks used for face protection, to make waterproof automotive seat covers, in liquid and sheet-applied elastomeric roof membranes or flashings, and in

12210-460: Was not finally abolished until 1946. In 1930, Mahatma Gandhi led a crowd of 100,000 protestors on the "Dandi March" or " Salt Satyagraha ", during which they made their own salt from the sea as a demonstration of their opposition to the colonial salt tax . This act of civil disobedience inspired numerous Indians and transformed the Indian independence movement into a national struggle. Salt

12321-482: Was prized by the ancient Hebrews , Greeks , Romans , Byzantines , Hittites , Egyptians , and Indians . Salt became an important article of trade and was transported by boat across the Mediterranean Sea , along specially built salt roads , and across the Sahara on camel caravans . The scarcity and universal need for salt have led nations to go to war over it and use it to raise tax revenues. Salt

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