The Salt Industry Commission was an organization created in 758, during the decline of Tang dynasty China, used to raise tax revenue from the state monopoly of the salt trade, or salt gabelle. The commission sold salt to private merchants at a price that included a low but cumulatively substantial tax, which was passed on by the merchants at the point of sale. This basic mechanism of an indirect tax collected by private merchants supervised by government officials endured to the mid-20th century. The salt tax enabled a weak government to sustain itself; the government need control only the few regions that produced salt.[1] Plans to end the government monopoly on salt by 2016 were announced in 2014.[2]
History
Following the An Lushan Rebellion (756–763) revenues from the land tax began to fall. The equal-field system that sustained the land tax was undermined by the aristocracy and Buddhist monasteries acquiring large tracts of land, decreasing the amount of land which was taxable.[3] To compensate the state found a new mechanism for the taxation of salt. In 758, Chancellor Liu Yan created a Salt and Iron Commission. Liu had already proved his worth by using impressed labor to dredge the long silted-over canal connecting the Huai and Yellow rivers; this project lowered transport costs, relieved food shortages, and increased tax revenues with little government investment. The Huai river ran through Northern Jiangsu, the location of coastal salt marshes which were the major source of salt. Liu realized that if the government could control these areas, it could sell the salt at a monopoly price to merchants, who would pass the price difference on to their customers. This monopoly price was an indirect tax which was reliably collected in advance without having to control the areas where the salt was consumed.[1] The commission formed to oversee the new scheme was headed by the salt commissioner (yantie shi), a financial specialist, which was uncharacteristic of the Tang unspecialized political administration.[4]
Effects
Salt was to be sold only at regional offices by licensed producers, and then only to licensed merchants at marked up prices. The distribution by merchants ensured the effects of the policy penetrated into areas where the central government had limited authority.[4] The merchants then passed on the high cost of salt to consumers. Peasants were most affected as they spent a higher percentage of their incomes on basic food goods. By 779, taxation of salt quickly accounted for over half of government revenues.[4]
List of salt commissioners
 |
See also
References
- Ebrey, Patricia, et al. "East Asia: A Cultural, Social, and Political History to 1800" (Boston: Houghton Mifflin Company, 2009) p. 85.
https://en.wikipedia.org/wiki/Salt_Commission
https://en.wikipedia.org/wiki/Royal_Saltworks_at_Arc-et-Senans
Salt mining extracts natural salt deposits from underground. The mined salt is usually in the form of halite (commonly known as rock salt), and extracted from evaporite formations.[1]
History
Before the advent of the modern internal combustion engine and earth-moving equipment, mining salt was one of the most expensive and dangerous of operations because of rapid dehydration caused by constant contact with the salt (both in the mine passages and scattered in the air as salt dust) and of other problems caused by accidental excessive sodium intake. Salt is now plentiful, but until the Industrial Revolution, it was difficult to come by, and salt was often mined by slaves or prisoners. Life expectancy for the miners was low.
Ancient China was among the earliest civilizations in the world with cultivation and trade in mined salt.[2] They first discovered natural gas when they excavated rock salt. The Chinese writer, poet, and politician Zhang Hua of the Jin dynasty wrote in his book Bowuzhi how people in Zigong, Sichuan, excavated natural gas and used it to boil a rock salt solution.[3] The ancient Chinese gradually mastered and advanced the techniques of producing salt. Salt mining was an arduous task for them, as they faced geographical and technological constraints. Salt was extracted mainly from the sea, and salt works in the coastal areas in late imperial China equated to more than 80 percent of national production.[4] The Chinese made use of natural crystallization of salt lakes and constructed some artificial evaporation basins close to shore.[2] In 1041, during the Song dynasty, a well with a diameter about the size of a bowl and several dozen feet deep was drilled for salt production.[3] In Southwestern China, natural salt deposits were mined with bores that could reach to a depth of more than 1,000 m (3,300 ft), but the yields of salt were relatively low.[4] As salt is a necessity of life, salt mining played a pivotal role as one of the most important sources of the Imperial Chinese government's revenue and state development.[4]
Most modern salt mines are privately operated or operated by large multinational companies such as K+S, AkzoNobel, Cargill, and Compass Minerals.
Mining regions around the world
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Some notable salt mines include:
| Country | Site(s) |
|---|---|
| Austria | Hallstatt and Salzkammergut. |
| Bosnia and Herzegovina | Tuzla |
| Bulgaria | Provadiya; and Solnitsata, an ancient town which Bulgarian archaeologists regard as the oldest in Europe and the site of a salt-production facility approximately six millennia ago.[5] |
| Canada | Sifto Salt Mine[6] in Goderich, Ontario, which, at 1.5 miles (2.4 km) wide and 2 miles (3.2 km) long, is one of the largest salt mines in the world extending 7 km2 (2.7 sq mi).[7][8][need quotation to verify] |
| Colombia | Zipaquirá |
| England | The "-wich towns" of Cheshire and Worcestershire. |
| Ethiopia, Eritrea, Djibouti | Danakil Desert, where manual labor is used.[9] |
| Germany | Rheinberg, Berchtesgaden, Heilbronn |
| Republic of Ireland | Mountcharles |
| Italy | Racalmuto, Realmonte and Petralia Soprana[10] within the production sites managed by Italkali. |
| Morocco | Société de Sel de Mohammedia (Mohammedia Rock Salt company) near Casablanca |
| Northern Ireland | Kilroot, near Carrickfergus, more than a century old and containing passages whose combined length exceeds 25 km. |
| Pakistan | Khewra Salt Mines, the world's second largest salt-mining operation, spanning over 300 km. It was first discovered by a horse of Alexander the Great. The mine is still operation till today. |
| Poland | Wieliczka and Bochnia, both established in the mid-13th century and still operating, mostly as museums. Kłodawa Salt Mine. |
| Romania | Slănic (with Salina Veche, Europe's largest salt mine), Cacica, Ocnele Mari, Salina Turda, Târgu Ocna, Ocna Sibiului, Praid and Salina Ocna Dej. |
| Russia |
|
| Ukraine | Soledar Salt Mine in Soledar, Donetsk oblast. |
| United States |
|
Idiomatic use
In slang, the term salt mines, and especially the phrase back to the salt mines, refers ironically to one's workplace, or a dull or tedious task. This phrase originates from c. 1800 in reference to the Russian practice of sending prisoners to forced labor in Siberian salt mines.[15][16]
See also
- Salt mines
- General
References
Sifto Canada Inc. [...] (Goderich Mine)
- Houston, Natalie (2010-01-25). "The Salt Mines. Really??". The Chronicle of Higher Education Blogs: ProfHacker. Retrieved 2020-01-12.
External links
https://en.wikipedia.org/wiki/Salt_mining
Sea salt is salt that is produced by the evaporation of seawater. It is used as a seasoning in foods, cooking, cosmetics and for preserving food. It is also called bay salt,[1] solar salt,[2] or simply salt. Like mined rock salt, production of sea salt has been dated to prehistoric times.
Composition
Commercially available sea salts on the market today vary widely in their chemical composition. Although the principal component is sodium chloride, the remaining portion can range from less than 0.2 to 10% of other salts. These are mostly calcium, potassium, and magnesium salts of chloride and sulfate with substantially lesser amounts of many trace elements found in natural seawater. Though the composition of commercially available salt may vary, the ionic composition of natural saltwater is relatively constant.[3]
| Concentration of ion in sea water[3] | mg/l |
|---|---|
| Chloride | 18 980 |
| Sodium | 10 556 |
| Sulfate | 2 649 |
| Magnesium | 1 262 |
| Calcium | 400 |
| Potassium | 380 |
| Bicarbonate | 140 |
| Bromide | 65 |
| Borate | 26 |
| Strontium | 13 |
| Fluoride | 1 |
| Silicate | 1 |
| Iodide | <1 |
| Total dissolved solids (TDS) | 34 483 |
Historical production
.jpg)
Sea salt is mentioned in the Vinaya Pitaka, a Buddhist scripture compiled in the mid-5th century BC.[4] The principle of production is evaporation of the water from the sea brine. In warm and dry climates this may be accomplished entirely by using solar energy, but in other climates fuel sources have been used. Modern sea salt production is almost entirely found in Mediterranean and other warm, dry climates.[5]
Such places are today called salt works, instead of the older English word saltern. An ancient or medieval saltern was established where there was:
- Access to a market for the salt[6]
- A gently shelving coast, protected from exposure to the open sea
- An inexpensive and easily worked fuel supply, or preferably the sun
- Another trade, such as pastoral farming or tanning—which benefited from proximity to the saltern (by producing leather, salted meat, etc.) and provided the saltern with a local market
In this way, salt marsh, pasture (salting), and salt works (saltern) enhanced each other economically. This was the pattern during the Roman and medieval periods around The Wash, in eastern England.[6] There, the tide brought the brine, the extensive saltings provided the pasture, the fens and moors provided the peat fuel, and the sun sometimes shone.
The dilute brine of the sea was largely evaporated by the sun. In Roman areas, this was done using ceramic containers known as briquetage.[6] Workers scraped up the concentrated salt and mud slurry and washed it with clean sea water to settle impurities out of the now concentrated brine. They poured the brine into shallow pans (lightly baked from local marine clay) and set them on fist-sized clay pillars over a peat fire for final evaporation. Then they scraped out the dried salt and sold it.
In traditional salt production in the Visayas Islands of the Philippines, salt are made from coconut husks, driftwood, or other plant matter soaked in seawater for at least several months. These are burned into ash then seawater is run through the ashes on a filter. The resulting brine is then evaporated in containers. Coconut milk is sometimes added to the brine before evaporation. The practice is endangered due to competition with cheap industrially-produced commercial salt. Only two traditions survive to the present day: asín tibuok and túltul (or dúkdok).[7][8]
In the colonial New World, slaves were brought from Africa to rake salt on various islands in the West Indies, Bahamas and particularly Turks and Caicos Islands.
Today, salt labelled "sea salt" in the US might not have actually come from the sea, as long as it meets the FDA's purity requirements.[9] All mined salts were originally sea salts since they originated from a marine source at some point in the distant past, usually from an evaporating shallow sea.[citation needed]
Taste
Some gourmets believe sea salt tastes better and has a better texture than ordinary table salt.[10] In applications that retain sea salt's coarser texture, it can provide a different mouthfeel, and may change flavor due to its different rate of dissolution. The mineral content also affects the taste. The colors and variety of flavors are due to local clays and algae found in the waters the salt is harvested from. For example, some boutique salts from Korea and France are pinkish gray, some from India are black. Black and red salts from Hawaii may even have powdered black lava and baked red clay added in.[11] Some sea salt contains sulfates.[12] It may be difficult to distinguish sea salt from other salts, such as pink Himalayan salt, Maras salt from the ancient Inca hot springs, or rock salt (halite)[citation needed].
Black lava salt is a marketing term for sea salt harvested from various places around the world that has been blended and colored with activated charcoal. The salt is used as a decorative condiment to be shown at the table.[13]
Health
The nutritional value of sea salt and table salt are about the same as they are both primarily sodium chloride.[14][15] Table salt is more processed than sea salt to eliminate minerals and usually contains an additive such as silicon dioxide to prevent clumping.[14]
Iodine, an element essential for human health,[16] is present only in small amounts in sea salt.[17] Iodised salt is table salt mixed with a minute amount of various salts of the element iodine.
Studies have found some microplastic contamination in sea salt from the US, Europe and China.[18] Sea salt has also been shown to be contaminated by fungi that can cause food spoilage as well as some that may be mycotoxigenic.[19]
In traditional Korean cuisine, jugyeom (죽염, 竹鹽), which means "bamboo salt", is prepared by roasting salt at temperatures between 800 and 2000 °C[20] in a bamboo container plugged with mud at both ends. This product absorbs minerals from the bamboo and the mud, and is claimed to increase the anticlastogenic and antimutagenic properties of the fermented soybean paste known in Korea as doenjang.[21] However, these claims are not substantiated by high-quality studies.
See also
References
- Shahidi, Fereidoon; John Shi; Ho, Chi-Tang (2005). Asian functional foods. Boca Raton: CRC Press. p. 575. ISBN 978-0-8247-5855-4.
External links
Media related to Sea salt at Wikimedia Commons
https://en.wikipedia.org/wiki/Sea_salt
Fleur de sel ("flower of salt" in French; French pronunciation: [flœʁ də sɛl]) or flor de sal (also "flower of salt" in Portuguese, Spanish and Catalan) is a salt that forms as a thin, delicate crust on the surface of seawater as it evaporates. Fleur de sel has been collected since ancient times (it was mentioned by Pliny the Elder in his book Natural History), and was traditionally used as a purgative and salve. It is now used as a finishing salt to flavor and garnish food.[1] The name comes from the flower-like patterns of crystals in the salt crust.
Harvesting
One method of gathering sea salt is to draw seawater into marsh basins or salt pans and allow the water to evaporate, leaving behind the salt that was dissolved in it. As the water evaporates, most of the salt precipitates out on the bottom of the marsh or pan (and is later collected as ordinary sea salt), but some salt crystals float on the surface of the water, forming a delicate crust of intricate pyramidal crystals. This is fleur de sel. The delicacy requires that it be harvested by hand, so this is done with traditional methods using traditional tools. In France, the workers who collect fleur de sel are called paludiers, and they employ a wooden rake called a lousse à fleur[2] to gently rake it from the water. In Portugal, a butterfly-shaped sieve called a borboleta is used instead.[3] It is then put in special boxes so that it will dry in the sun, and to avoid disturbing the flakes as it is transported for packaging. Historically, the workers who harvested fleur de sel were women, because it was believed that as the salt crystals were so delicate, they needed to be collected by "the more delicate sex."[4] Because it is scraped from the salt marsh like cream from milk, fleur de sel has been called "the cream of the salt pans."[5] It is also called "the caviar of sea salts."[6]
Fleur de sel can be collected only when it is very sunny, dry, and with slow, steady winds.[3] Because of the nature of its formation, fleur de sel is produced in small quantities. At Guérande, France, each salt marsh produces only about one kilo (2.2 pounds) per day.[4] Because of this and the labor-intensive way in which it is harvested, fleur de sel is the most expensive of salts.[7]
This method of salt formation and collection results in salt crystals that are not uniform. The salt also has a much higher amount of moisture than common salt (up to 10%[8] compare to 0.5% for common salt[9]), allowing the crystals to stick together in snowflake-like forms. The moisture means that fleur de sel won't dissolve right away on your tongue, so the taste lingers. Also, since it is unrefined, it is not just sodium chloride. Other minerals, like calcium, and magnesium chloride, give it a more complex flavor. These chemicals make fleur de sel taste even saltier than salt,[10] and give it what has been described as the flavor of the sea. Trace mineral content depends upon the location at which it is harvested, so the flavor varies with point of origin.
Fleur de sel is rarely the pure white of table salt. It is often pale gray or off-white from clay from the salt marsh beds. Sometimes it has a faintly pink tinge from the presence of Dunaliella salina, a type of pink microalga commonly found in salt marshes.[11] However fleur de sel from Ria Formosa[5] in Portugal is white.
Uses
Only about 5% of salt is used for cooking,[12] but fleur de sel is used only to flavor food. It is not used in place of salt during the cooking process, instead, it is added just before serving, like a garnish, a "finishing salt," to boost the flavor of eggs, fish, meat, vegetables, chocolate, and caramel.[4]
Sources
Sea salt has been gathered around the world for millennia, but over the last thousand years, fleur de sel was only harvested in France. Elsewhere it was collected and discarded. As the market for specialty salts has grown, companies have begun to harvest fleur de sel for export wherever the geographic and meteorological conditions are favorable.
Europe
Traditional French fleur de sel is collected off the coast of Brittany, most notably in the town of Guérande (called Fleur de Sel de Guérande), but also in Noirmoutier, and Île de Ré.[13]
Greeks have harvested sea salt and fleur de sel (ανθος αλατιού) along the Mediterranean Sea coast, particularly the Mani Peninsula of Lakonia[14] and Missolonghi, from ancient times.[15]
Flor de sal is harvested in Portugal, mostly in the Aveiro District[16] and in the Algarve,[17][18] but also in the salt marshes of Castro Marim,[19] at the mouth of the Guadiana River that forms the border to Spain. Roman ruins near Ria Formosa specifically suggest that there has been a long history of sea salt production here. Before the invention of salt mining, Portugal's sea salt production helped to solidify its place as a world power.[17] However, when mechanical salt mining made salt inexpensive, demand for Portugal's sea salt dropped due to its expense. For centuries flor de sal was scraped away and either discarded or given to workers, as its presence disturbed the evaporation that was creating the sea salt underneath.[20] The process of harvesting flor de sal for sale was reintroduced in 1997 by Necton, with a grant to develop ways to capitalize Portugal's natural resources.[5] Necton's flor de sal is whiter than the fleur de sel from Guérande, and is said to have the more robust flavor of the Atlantic as opposed to Guérande's milder Biscay Bay flavor.[21] Due to Portugal's laws regarding the grading of salt, Necton's flor de sal is exported to France and marketed by companies who also market fleur de sel.[5]
Spain also produces high quality flor de sal in the Ebro Delta on the mainland[22] and the Salinas d'Es Trenc on the island of Majorca[23] and in the Salinas de la Trinidad in the Ebro Delta.[24] Majorca has a long history of salt production, dating to the Phoenicians and the Romans,[25] but flor de sel was mostly kept for local use until Katja Wöhr arrived from Switzerland in 2002 and convinced local officials to allow her to harvest it in Es Trenc.[26] She worked with British chef Marc Fosh to develop mixtures of flor de sal with herbs and spice blends added, such as orange, lemon, black olive, lavender, rosemary, dried rose petals, curry spices, and beetroot.[27][28]
Spain's Canary Islands are also a source of flor de sal. Saltworks have operated on La Palma and Lanzarote for centuries,[29] but the flor de sal that resulted was kept for the use of the workers until 2007, when the salt gained gourmet status. The culinary rediscovery of fleur de sel and other gourmet salts has saved small scale artisanal saltworks in the Canaries, which were in rapid decline.[30]
Americas
Canada now produces high quality fleur de sel from the Pacific Ocean off Vancouver Island.[31] The colder climate adds extra crunch and reduces the flakiness. Unlike traditional European fleur de sel, which crystallizes naturally in the sun, Canadian fleur de sel makers heat their seawater to force evaporation.[32]
Mexico has produced both sea salt and flor de sal since Aztec times from the Lagoon of Cuyutlán on the Pacific Coast. There is also a museum in Cuyutlán, dedicated to the history and technique of flor de sal production.[33]
Flor de sal is also harvested along the beaches of Celestun in Yucatan, Mexico where Mayans cultivated salt 1,500 years ago for its distribution throughout Mesoamerican trade routes extending to Guatemala, Central America and the Caribbean.[34]
Brazil started producing flor de sal in 2008 in the traditional salt-producing area of Macau, in the state of Rio Grande do Norte.[35] The salt kept for use in Brazil is iodized though, as required by the Brazilian law for all salt intended for human consumption, but that intended for export is not.[6] The main producer is ArtSal - Flor De Sal.[36]
Mineral composition
Because it is harvested naturally from the sea and is usually not refined, fleur de sel has more mineral complexity than common table salt. The following is a chemical analysis of Flos Salis, a flor de sal by Portuguese company Marisol:[19]
| Mineral | Quantity |
|---|---|
| Sodium chloride | 97% (in dry matter) |
| Moisture | 6.5% |
| Calcium | 0.1% |
| Magnesium | 0.4% |
| Potassium | 0.2% |
| Iron | 5 mg/kg |
| Insolubles | < 0.02% |
See also
References
- Rodrigues, R.M., Jr. (September 2008). "ArtSal Flor De Sal - Company producing the legitimate Flower of salt in Brazil since 2008". ArtSal - Flor de Sal (Fleur de Sel). 1 (1): 1–10. Archived from the original on 27 September 2020. Retrieved 31 January 2018.
External links
- The Wall Street Journal on the Camargue saltworks
- de sal/como.html Diagrams and explanations of a salt pan works, from D'Aveiro, a Portuguese salt manufacturer.
https://en.wikipedia.org/wiki/Fleur_de_sel
Iodised salt (also spelled iodized salt) is table salt mixed with a minute amount of various salts of the element iodine. The ingestion of iodine prevents iodine deficiency. Worldwide, iodine deficiency affects about two billion people and is the leading preventable cause of intellectual and developmental disabilities.[1][2] Deficiency also causes thyroid gland problems, including endemic goitre. In many countries, iodine deficiency is a major public health problem that can be cheaply addressed by purposely adding small amounts of iodine to the sodium chloride salt.
Iodine is a micronutrient and dietary mineral that is naturally present in the food supply in some regions, especially near sea coasts but is generally quite rare in the Earth's crust since iodine is a so-called heavy element, and abundance of chemical elements generally declines with greater atomic mass. Where natural levels of iodine in the soil are low and the iodine is not taken up by vegetables, iodine added to salt provides the small but essential amount of iodine needed by humans.
An opened package of table salt with iodide may rapidly lose its iodine content in high temperature and high relative humidity conditions through the process of oxidation and iodine sublimation.[3]
Chemistry, biochemistry and nutritional aspects
Four inorganic compounds are used as iodide sources, depending on the producer: potassium iodate, potassium iodide, sodium iodate, and sodium iodide. Any of these compounds supplies the body with its iodine required for the biosynthesis of thyroxine (T4) and triiodothyronine (T3) hormones by the thyroid gland. Animals also benefit from iodine supplements, and the hydrogen iodide derivative of ethylenediamine is the main supplement to livestock feed.[4]
Salt is an effective vehicle for distributing iodine to the public because it does not spoil and is consumed in more predictable amounts than most other commodities.[citation needed] For example, the concentration of iodine in salt has gradually increased p Switzerland: 3.75 mg/kg in 1952, 7.5 mg/kg in 1962, 15 mg/kg in 1980, 20 mg/kg in 1998, and 25 mg/kg in 2014.[5] These increases were found to improve iodine status in the general Swiss population.[6]
Salt that is iodized may slowly lose its iodine content by exposure to excess air over long periods.[7]
Production
Edible salt can be iodised by spraying it with a potassium iodate or potassium iodide solution. 57 grams of potassium iodate, costing about US$1.15 (in 2006), is required to iodise a ton (2,000 pounds) of salt.[1] Dextrose is added as a stabilizer to prevent potassium iodide from oxidizing and evaporating. Anti-caking agents such as calcium silicate are commonly added to table salt to prevent clumping.[8]
In public health initiatives
Worldwide, iodine deficiency affects two billion people and is the leading preventable cause of intellectual and developmental disabilities.[1][2] According to public health experts, iodisation of salt may be the world's simplest and most cost-effective measure available to improve health, only costing US$0.05 per person per year.[1] At the World Summit for Children in 1990, a goal was set to eliminate iodine deficiency by 2000. At that time, 25% of households consumed iodised salt, a proportion that increased to 66% by 2006.[1]
Salt producers are often, although not always, supportive of government initiatives to iodize edible salt supplies. Opposition to iodization comes from small salt producers who are concerned about the added expense, private makers of iodine pills, concerns about promoting salt intake, and unfounded rumors that iodization causes AIDS or other illnesses.[1]
The United States Food and Drug Administration recommends[9] 150 micrograms (0.15 mg) of iodine per day for adults.
Argentina
Since 8 May 1967 salt for human or animal use must be iodised, according to the Law 17,259.[10]
Syria
In the end of eighties of last century, a Syrian endocrinologist Samir Ouaess conducted a research on hypothyroidism and noticed that 90 percent of Syrians suffer from hypothyroidism, 50 percent suffer from health problems as a result of Thyroid deficiency, and 10 percent of students suffer from a decline in their academic level due to that problem. Dr. Ouaess linked these results with the fact that natural drinking water sources in Syria do not contain enough minerals. He presented the result of that study to the Syrian Ministry of Health. After that, adding iodine to salt became almost mandatory till 2021, when the Syrian government canceled the iodization of salt and as a result of economic problems related to economic sanctions.
Australia
Australian children were identified as being iodine deficient in a survey conducted between 2003 and 2004.[11] As a result of this study the Australian Government mandated that all bread with the exception of "organic" bread must use iodised salt.[12] There remains concern that this initiative is not sufficient for pregnant and lactating women.[13]
Brazil
Iodine Deficiency Disorders were detected as a major public health issue by Brazilian authorities in the 1950s when about 20% of the population had a goitre.[14] The National Agency for Sanitary Vigilance (ANVISA) is responsible for setting the mandatory iodine content of table salt. The Brazilian diet averages 12 g of table salt per day, more than twice the recommended value of 5 g a day. To avoid excess consumption of iodine, the iodizing of Brazilian table salt was reduced to 15–45 mg/kg in July 2013. Specialists criticized the move, saying that it would be better for the government to promote reduced salt intake, which would solve the iodine problem as well as reduce the incidence of high blood pressure.[15]
Canada
Salt sold to consumers in Canada for table and household use must be iodized with 0.01% potassium iodide. Sea salt and salt sold for other purposes, such as pickling, may be sold uniodized.[16]
China
Much of the Chinese population lives inland, far from sources of dietary iodine. In 1996, the Chinese Ministry of Public Health estimated that iodine deficiency was responsible for 10 million cases of intellectual developmental disorders in China.[17] Chinese governments have held a legal monopoly on salt production since 119 BCE and began iodizing salt in the 1960s, but market reforms in the 1980s led to widespread smuggling of non-iodized salt from private producers. In the inland province of Ningxia, only 20% of salt consumed was sold by the China National Salt Industry Corporation. The Chinese government responded by cracking down on smuggled salt, establishing salt police with 25,000 officers to enforce the salt monopoly. Consumption of iodized salt reached 90% of the Chinese population by 2000.[18]
India
India and all of its states ban the sale of non-iodized salt for human consumption. However, implementation and enforcement of this policy are imperfect; a 2009 survey found that 9% of households used non-iodized salt and that another 20% used insufficiently iodized salt.[19]
Iodised salt was introduced to India in the late 1950s. Public awareness was increased by special programs and initiatives, both governmental and nongovernmental. As of now, iodine deficiency is only present in a few isolated regions which are still unreachable. In India, some people use Himalayan rock salt. Rock salt however is low in iodine and should be consumed only when there are other iodine-rich foods in diet.[citation needed]
Iran
A national program with iodized salt started in 1992. A national survey of 1990 revealed the prevalence of iodine deficiency to be 20-80% in different parts of Iran indicating a major public health problem. Central provinces, far from the sea, had the highest prevalence of iodine deficiency. The national salt enrichment program had a great rapid success. Prevalence of goiter in Iran dropped dramatically. The national survey in 1996 reported 40% of boys and 50% of girls have goiter. The 3rd national survey in 2001 showed that the total goiter rate is 9.8%. In 2007, the 4th national survey was conducted 17 years after iodized salt consumption by Iranian households. In this study the total goiter rate was 5.7%.[2]</ref>
Concerns of iodine deficiency have raised over recent years due to consumption of non-iodized salts especially sea salt which is strongly suggested by traditional medicine workers in Iran. Many of whom have not any academic studies.
Kazakhstan
Kazakhstan, a country in Central Eurasia in which local food supplies seldom contain sufficient iodine, has drastically reduced iodine deficiency through salt iodization programs. Campaigns by the government and non-profit organizations to educate the public about the benefits of iodized salt began in the mid-1990s, with iodization of edible salt becoming legally mandatory in 2002.[1]
Nepal
The Salt Trading Corporation has been distributing Iodized Salt in Nepal since 1963.[20] 98% of the Population uses Iodized Salt. Utilising non-Iodised salt for human consumption is prohibited.[citation needed] Salt costs about US$0.27 a Kilo.[21]
Philippines
On December 20, 1995, Philippine President Fidel V. Ramos signed Republic Act 8172: An Act for Salt Iodization Nationwide (ASIN).[22]
Romania
According to the 568/2002 law signed by the Romanian parliament and republished in 2009, since 2002 iodized salt is distributed mandatory in the whole country. It is used mandatory on the market for household consumption, in bakeries, and for pregnant women. Iodised salt is optional though for animal consumption and the food industry, although widely used. The salt iodization process has to assure a minimum of 30mg iodine/kg of salt. [23][24]
South Africa
The South African government instructed that all salt for sale was to be iodised after December 12, 1995.[25][26]
United States
Iodized salt is not mandatory in the US but it is widely available.
In the U.S. in the early 20th century, goitres were especially prevalent in the region around the Great Lakes and the Pacific Northwest.[27] David Murray Cowie, a professor of paediatrics at the University of Michigan, led the U.S. to adopt the Swiss practice of adding sodium iodide or potassium iodide to table and cooking salt. On May 1, 1924, iodised salt was sold commercially in Michigan.[28] By the fall of 1924, Morton Salt Company began distributing iodised salt nationally.
A 2017 study found that the introduction of iodized salt in 1924 raised the IQ for the one-quarter of the population most deficient in iodine.[29] These findings "can explain roughly one decade's worth of the upward trend in IQ in the United States (the Flynn effect)".[29] The study also found "a large increase in thyroid-related deaths following the countrywide adoption of iodized salt, which affected mostly older individuals in localities with high prevalence of iodine deficiency".[29] A 2013 study found a gradual increase in average intelligence of 1 standard deviation, 15 points in iodine-deficient areas and 3.5 points nationally after the introduction of iodized salt.[30]
A 2018 paper found that the nationwide distribution of iodine-fortified salt increased incomes by 11%, labor force participation by 0.68 percentage points and full-time work by 0.9 percentage points. According to the study, "These impacts were largely driven by changes in the economic outcomes of young women. In later adulthood, both men and women had higher family incomes due to iodization."[31]
No-additive salts for canning and pickling
In contrast to table salt, which often contains iodide as well as anti-caking ingredients, special canning and pickling salt is made for producing the brine to be used in pickling vegetables and other foodstuffs. Contrary to popular belief, however, iodized salt affects neither color, taste, nor consistency of pickles.[32]
Fortification of salt with other elements
Double-fortified salt (DFS)
Salt can also be double-fortified with iron and iodine.[33] The iron is microencapsulated with stearin to prevent it from reacting with the iodine in the salt. By providing iron in addition to iodine in the convenient delivery vehicle of salt, it could serve as a sustainable approach to combating both iodine and iron deficiency disorders in areas where both deficiencies are prevalent.[34]
Adding iron to iodized salt is complicated by several chemical, technical, and organoleptic issues. Since a viable DFS premix became available for scale-up in 2001, a body of scientific literature has been emerging to support the DFS initiative including studies conducted in Ghana, India, Côte d'Ivoire, Kenya and Morocco.[35]
Fluoridated salt
In some countries, table salt is treated with potassium fluoride to enhance dental health.[36]
Diethylcarbamazine
In India and China, diethylcarbamazine has been added to salt to combat lymphatic filariasis.[37]
See also
- Basil Hetzel
- Enriched flour serves an analogous function to "enriched salt".
- History of salt
- Lugol's iodine
- Sea salt
- Water fluoridation, a similar public health intervention
- Food fortification
Notes
- [1] WHO: Unfulfilled potential: using diethylcarbamazine-fortified salt to eliminate lymphatic filariasis
References
- Markel Howard (1987). "When It Rains It Pours: Endemic Goiter, Iodized Salt, and David Murray Cowie MD". American Journal of Public Health. 77 (2): 219–229. doi:10.2105/AJPH.77.2.219. PMC 1646845. PMID 3541654.
- 21 CFR 101.9 (c)(8)(iv)
- Newton County – Encyclopedia of Arkansas
External links
| Authority control: National |
|---|
https://en.wikipedia.org/wiki/Iodised_salt
https://en.wikipedia.org/wiki/Iodised_salt
https://en.wikipedia.org/wiki/Salt_substitute
https://en.wikipedia.org/wiki/Potassium_chloride
https://en.wikipedia.org/wiki/Monosodium_glutamate
https://en.wikipedia.org/wiki/Cyclic_salt
https://en.wikipedia.org/wiki/Curing_salt
https://en.wikipedia.org/wiki/Celery_salt
https://en.wikipedia.org/wiki/Calcium_chloride
https://en.wikipedia.org/wiki/Bittern_(salt)
https://en.wikipedia.org/wiki/Alberger_process
https://en.wikipedia.org/wiki/Alaea_salt
https://en.wikipedia.org/wiki/Abraum_salts
https://en.wikipedia.org/wiki/Himalayan_salt
https://en.wikipedia.org/wiki/Potassium_nitrate
https://en.wikipedia.org/wiki/Sodium_chloride
https://en.wikipedia.org/wiki/Truffle#Culinary_use
https://en.wikipedia.org/wiki/Sodium_nitrate
Sel gris (pl. sels gris, "gray salt" in French) is a coarse granular sea salt popularized by the French. Sel gris comes from the same solar evaporation salt pans as fleur de sel but is harvested differently; it is allowed to come into contact with the bottom of the salt pan before being raked, hence its gray color. Sel gris is coarser than fleur de sel but is also a moist salt, typically containing 13 percent residual moisture.[1]
A salt evaporation pond is a shallow artificial salt pan designed to extract salts from sea water or other brines. The salt pans are shallow and expansive, allowing sunlight to penetrate and reach the seawater. Natural salt pans are formed through geological processes, where water evaporating, leaving behind salts deposits. Some salt evaporation ponds are only slightly modified from their natural version, such as the ponds on Great Inagua in the Bahamas, or the ponds in Jasiira, a few kilometres south of Mogadishu, where seawater is trapped and left to evaporate in the sun.
The seawater or brine is fed into large ponds and water is drawn out through natural evaporation which allows the salt to be subsequently harvested.
The ponds also provide a productive resting and feeding ground for many species of waterbirds, which may include endangered species.[1] The ponds are commonly separated by levees. Salt evaporation ponds may also be called salterns, salt works or salt pans.
https://en.wikipedia.org/wiki/Salt_evaporation_pond
| Water desalination
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| Methods |
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Solar desalination is a desalination technique powered by solar energy. The two common methods are direct (thermal) and indirect (photovoltaic).[1]
History
Solar distillation has been used for thousands of years. Early Greek mariners and Persian alchemists produced both freshwater and medicinal distillates. Solar stills were the first method used on a large scale to convert contaminated water into a potable form.[2]
In 1870 the first US patent was granted for a solar distillation device to Norman Wheeler and Walton Evans.[3] Two years later in Las Salinas, Chile, Swedish engineer Charles Wilson began building a solar distillation plant to supply freshwater to workers at a saltpeter and silver mine. It operated continuously for 40 years and distilled an average of 22.7 m3 of water a day using the effluent from mining operations as its feed water.[4]
Solar desalination in the United States began in the early 1950s when Congress passed the Conversion of Saline Water Act, which led to the establishment of the Office of Saline Water (OSW) in 1955. OSW's main function was to administer funds for desalination research and development projects.[5] One of five demonstration plants was located in Daytona Beach, Florida. Many of the projects were aimed at solving water scarcity issues in remote desert and coastal communities.[4] In the 1960s and 1970s several distillation plants were constructed on the Greek isles with capacities ranging from 2000 to 8500 m3/day.[2] In 1984 a plant was constructed in Abu-Dhabi with a capacity of 120 m3/day that is still in operation.[4] In Italy, an open source design called "the Eliodomestico" by Gabriele Diamanti was developed for personal costing $50.[6]
Of the estimated 22 million m3 daily freshwater produced through desalination worldwide, less than 1% uses solar energy.[2] The prevailing methods of desalination, MSF and RO, are energy-intensive and rely heavily on fossil fuels.[7] Because of inexpensive methods of freshwater delivery and abundant low-cost energy resources, solar distillation has been viewed as cost-prohibitive and impractical.[2] It is estimated that desalination plants powered by conventional fuels consume the equivalent of 203 million tons of fuel a year.[2]
Methods
In the direct (distillation) method, a solar collector is coupled with a distilling mechanism.[9] Solar stills of this type are described in survival guides, provided in marine survival kits, and employed in many small desalination and distillation plants. Water production is proportional to the area of the solar surface and solar incidence angle and has an average estimated value of 3–4 litres per square metre (0.074–0.098 US gal/sq ft).[2] Because of this proportionality and the relatively high cost of property and material for construction, distillation tends to favor plants with production capacities less than 200 m3/d (53,000 US gal/d).[2]
Indirect desalination employs a solar collection array, consisting of photovoltaic and/or fluid-based thermal collectors, and a separate conventional desalination plant.[9] Many arrangements have been analyzed, experimentally tested and deployed. Categories include multiple-effect humidification (MEH), multi-stage flash distillation (MSF), multiple-effect distillation (MED), multiple-effect boiling (MEB), humidification–dehumidification (HDH), reverse osmosis (RO), and freeze-effect distillation.[7]
Indirect solar desalination systems using photovoltaic (PV) panels and reverse osmosis (RO) have been in use since 2009. Output by 2013 reached 1,600 litres (420 US gal) per hour per system, and 200 litres (53 US gal) per day per square metre of PV panel.[10][11] Utirik Atoll in the Pacific Ocean has been supplied with fresh water this way since 2010.[12]
Indirect solar desalination by a form of humidification/dehumidification is in use in the seawater greenhouse.
Indirect
Large solar desalination plants typically use indirect methods.[13] Indirect solar desalination processes are categorized into single-phase processes (membrane based) and phase change processes (non-membrane based).[14] Single-phase desalination use photovoltaics to produce electricity that drive pumps.[15] Phase-change (or multi-phase) solar desalination is not membrane-based.[16]
Single-phase desalination processes include reverse osmosis and membrane distillation, where membranes filter water from contaminants.[14][16] As of 2014 reverse osmosis (RO) made up about 52% of indirect methods.[13][17][18] Pumps push salt water through RO modules at high pressure.[14][17] RO systems depend on pressure differences. A pressure of 55–65 bar is required to purify seawater. An average of 5 kWh/m3 of energy is typically required to run a large-scale RO plant.[17] Membrane distillation (MD) utilizes pressure difference from two sides of a microporous hydrophobic membrane.[17][19] Fresh water can be extracted through four MD methods: Direct Contact (DCMD), Air Gap (AGMD), Sweeping Gas (SGMD) and Vacuum (VMD).[17][19] An estimated water cost of $15/m3 and $18/m3 support medium-scale solar-MD plants.[17][20] Energy consumption ranges from 200 to 300 kWh/m3.[21]
Phase-change (or multi-phase) solar desalination[16][18][22] includes multi-stage flash, multi-effect distillation (MED), and thermal vapor compression (VC).[16] It is accomplished by using phase change materials (PCMs) to maximize latent heat storage and high temperatures.[23] MSF phase change temperatures range 80–120 °C, 40–100 °C for VC, and 50–90 °C for the MED method.[16][22] Multi-stage flash (MSF) requires seawater to travel through a series of vacuumed reactors held at successively lower pressures.[18] Heat is added to capture the latent heat of the vapor. As seawater flows through the reactors, steam is collected and is condensed to produce fresh water.[18] In Multi-effect distillation (MED), seawater flows through successively low pressure vessels and reuses latent heat to evaporate seawater for condensation.[18] MED desalination requires less energy than MSF due to higher efficiency in thermodynamic transfer rates.[18][22]
Direct
Direct methods use thermal energy to vaporize the seawater as part of a 2-phase separation. Such methods are relatively simple and require little space so they are normally used on small systems. However, they have a low production rate due to low operating temperature and pressure, so they are appropriate for systems that yield 200 m3/day.[24]
Single-effect
This uses the same process as rainfall. A transparent cover encloses a pan where saline water is placed. The latter traps solar energy, evaporating the seawater. The vapor condenses on the inner face of a sloping transparent cover, leaving behind salts, inorganic and organic components and microbes.
The direct method achieves values of 4-5 L/m2/day and efficiency of 30-40%.[25] Efficiency can be improved to 45% by using a double slope or an additional condenser.[26]
In a wick still, feed water flows slowly through a porous radiation-absorbing pad. This requires less water to be heated and is easier to change the angle towards the sun which saves time and achieves higher temperatures.
A diffusion still is composed of a hot storage tank coupled to a solar collector and the distillation unit. Heating is produced by the thermal diffusion between them.
Increasing the internal temperature using an external energy source can improve productivity.
Indirect multi-phase
Multi-stage flash distillation (MSF)
Multi-stage flash distillation is in widespread use. As of 2009, it accounted for roughly 45% of the world desalination capacity and 93% of thermal systems.[2]
In Margherita di Savoia, Italy a 50–60 m3/day MSF plant uses a salinity gradient solar pond. In El Paso, Texas a similar project produces 19 m3/day. In Kuwait a MSF facility uses parabolic trough collectors to provide solar thermal energy to produce 100 m3 of fresh water a day.[7] And in Northern China an experimental, automatic, unmanned operation uses 80 m2 of vacuum tube solar collectors coupled with a 1 kW wind turbine (to drive several small pumps) to produce 0.8 m3/day.[27]
MSF solar distillation has an output capacity of 6–60 L/m2/day versus the 3-4 L/m2/day standard output of a solar still.[7] MSF experience poor efficiency during start-up or low energy periods. Achieving highest efficiency requires controlled pressure drops across each stage and steady energy input. As a result, solar applications require some form of thermal energy storage to deal with cloud interference, varying solar patterns, nocturnal operation, and seasonal temperature changes. As thermal energy storage capacity increases a more continuous process can be achieved and production rates approach maximum efficiency.[28]
Freezing
Although it has only been used on demonstration projects, this indirect method based on crystallization of the saline water has the advantage of the low energy required. Since the latent heat of fusion of water is 6,01 kJ/mole and the latent heat of vaporization at 100 °C is 40,66 kJ/mole, it should be cheaper in terms of energy cost. Furthermore, the corrosion risk is lower too. There is however a disadvantage related with the difficulties of mechanically moving mixtures of ice and liquid. The process has not been commercialized yet due to cost and difficulties with refrigeration systems.
The most studied way of using this process is the refrigeration freezing. A refrigeration cycle is used to cool the water stream to form ice, and after that those crystals are separated and melted to obtain fresh water. There are some recent examples of this solar powered processes: the unit constructed in Saudi Arabia by Chicago Bridge and Iron Inc. in the late 1980s, which was shut down for its inefficiency.
Nevertheless, there is a recent study for the saline groundwater [29] concluding that a plant capable of producing 1 million gal/day would produce water at a cost of $1.30/1000 gallons. Being this true, it would be a cost-competitive device with the reverse osmosis ones.
Problems with thermal systems
Inherent design problems face thermal solar desalination projects. First, the system's efficiency is governed by competing heat and mass transfer rates during evaporation and condensation.[1]
Second, the heat of condensation is valuable because it takes large amounts of solar energy to evaporate water and generate saturated, vapor-laden hot air. This energy is, by definition, transferred to the condenser's surface during condensation. With most solar stills, this heat is emitted as waste heat.
Solutions
Heat recovery allows the same heat input to be reused, providing several times the water.[1]
One solution is to reduce the pressure within the reservoir. This can be accomplished using a vacuum pump, and significantly decreases the required heat energy. For example, water at a pressure of 0.1 atmospheres boils at 50 °C (122 °F) rather than 100 °C (212 °F).[30]
Solar humidification–dehumidification
The solar humidification–dehumidification (HDH) process (also called the multiple-effect humidification–dehumidification process, solar multistage condensation evaporation cycle (SMCEC) or multiple-effect humidification (MEH)[31] mimics the natural water cycle on a shorter time frame by distilling water. Thermal energy produces water vapor that is condensed in a separate chamber. In sophisticated systems, waste heat is minimized by collecting the heat from the condensing water vapor and pre-heating the incoming water source.[32]
Single-phase solar desalination
In indirect, or single phase, solar-powered desalination, two systems are combined: a solar energy collection system (e.g. photovoltaic panels) and a desalination system such as reverse osmosis (RO). The main single-phase processes, generally membrane processes, consist of RO and electrodialysis (ED). Single phase desalination is predominantly accomplished with photovoltaics that produce electricity to drive RO pumps. Over 15,000 desalination plants operate around the world. Nearly 70% use RO, yielding 44% of desalination.[33] Alternative methods that use solar thermal collection to provide mechanical energy to drive RO are in development.
Reverse osmosis
RO is the most common desalination process due to its efficiency compared to thermal desalination systems, despite the need for water pre-treatment.[34] Economic and reliability considerations are the main challenges to improving PV powered RO desalination systems. However, plummeting PV panel costs make solar-powered desalination more feasible.
Solar-powered RO desalination is common in demonstration plants due to the modularity and scalability of both PV and RO systems. An economic analysis[35] that explored an optimisation strategy[36] of PV-powered RO reported favorable results.
PV converts solar radiation into direct-current (DC) electricity, which powers the RO unit. The intermittent nature of sunlight and its variable intensity throughout the day complicates PV efficiency prediction and limits night-time desalination. Batteries can store solar energy for later use. Similarly, thermal energy storage systems ensure constant performance after sunset and on cloudy days.[37]
Batteries allow continuous operation. Studies have indicated that intermittent operations can increase biofouling.[38]
Batteries remain expensive and require ongoing maintenance. Also, storing and retrieving energy from the battery lowers efficiency.[38]
Reported average cost of RO desalination is US$0.56/m3. Using renewable energy, that cost could increase up to US$16/m3.[33] Although renewable energy costs are greater, their use is increasing.
Electrodialysis
Both electrodialysis (ED) and reverse electrodialysis (RED) use selective ion transport through ion exchange membranes (IEMs) due either to the influence of concentration difference (RED) or electrical potential (ED).
In ED, an electrical force is applied to the electrodes; the cations travel toward the cathode and anions travel toward the anode. The exchange membranes only allow the passage of its permeable type (cation or anion), hence with this arrangement, diluted and concentrated salt solutions are placed in the space between the membranes (channels). The configuration of this stack can be either horizontal or vertical. The feed water passes in parallel through all the cells, providing a continuous flow of permeate and brine. Although this is a well-known process electrodialysis is not commercially suited for seawater desalination, because it can be used only for brackish water (TDS < 1000 ppm).[33] Due to the complexity for modeling ion transport phenomena in the channels, performance could be affected, considering the non-ideal behavior presented by the exchange membranes.[39]
The basic ED process could be modified and turned into RED, in which the polarity of the electrodes changes periodically, reversing the flow through the membranes. This limits the deposition of colloidal substances, which makes this a self-cleaning process, almost eliminating the need for chemical pre-treatment, making it economically attractive for brackish water.[40]
The use ED systems began in 1954, while RED was developed in the 1970s. These processes are used in over 1100 plants worldwide. The main advantages of PV in desalination plants is due to its suitability for small-scale plants. One example is in Japan, on Oshima Island (Nagasaki), which has operated since 1986 with 390 PV panels producing 10 m3/day with dissolved solids (TDS) about 400 ppm.[40]
See also
References
- Al-Karaghouli, Ali; Renne, David; Kazmerski, Lawrence L. (February 2010). "Technical and economic assessment of photovoltaic-driven desalination systems". Renewable Energy. 35 (2): 323–328. doi:10.1016/j.renene.2009.05.018. ISSN 0960-1481.
External links
- Irving, Michael (2021-04-28). "Efficient solar desalination unit uses titanium-coated diaper material". New Atlas. Retrieved 2021-05-03.
https://en.wikipedia.org/wiki/Solar_desalination
https://en.wikipedia.org/wiki/Category:Water_technology
https://en.wikipedia.org/wiki/Category:Water_conservation
Saltwater soap, also called sailors' soap, is a potassium-based soap for use with seawater. Inexpensive common commercial soap will not lather or dissolve in seawater due to high levels of sodium chloride in the water. Similarly, common soap does not work as well as potassium-based soap in hard water where calcium replaces the sodium, making residual insoluble "scum" due to the insolubility of the soap residue. To be an effective cleaning agent, soap must be able to dissolve in water.[1][2][3][4][5][6][7]
Ordinary soap is a salt of a fatty acid.[8] Soaps are mainly used as surfactants for washing, bathing, and cleaning. Soaps for cleansing are made by treating vegetable or animal oils and fats with a strongly alkaline solution. Fats and oils are composed of triglycerides; three molecules of fatty acids are attached to a single molecule of glycerol.[9] The alkaline solution, which is often called lye (although the term "lye soap" refers almost exclusively to soaps made with sodium hydroxide), brings about a chemical reaction known as saponification. In this reaction, the triglyceride fats are first hydrolyzed into free fatty acids, and then these combine with the alkali to form crude soap: a combination of various soap salts, excess fat or alkali, water, and liberated glycerol (glycerin).[9]
Saltwater soaps are potassium salts rather than sodium salts. Both sodium and potassium are alkali metals. The relatively high concentration of salt (sodium chloride) in seawater lowers the solubility of soaps made with sodium hydroxide, due to the common ion effect, a form of salting out. Potassium soaps are more soluble in seawater than sodium soaps and so are more effective with seawater. In places that do not have freshwater or need to conserve it, cleaning can be done with the use of salt water and saltwater soap.
See also
- Elephant toothpaste
- Evaporator (marine)
- Feldspar
- Lithium soap
- Murphy Oil Soap
- Navy shower
- Potassium carbonate
- Potassium hydroxide
- Saponification value
References
- Cavitch, Susan Miller. The Natural Soap Book. Storey Publishing, 1994 ISBN 0-88266-888-9.
https://en.wikipedia.org/wiki/Saltwater_soap
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