Uyah atau uyah méja nyaéta mineral nu utamana disusun ku natrium klorida (NaCl), sanyawa kimia nu kaasup kana kelas uyah nu leuwih badag; uyah dina wangun alami mah minangka mineral kristalin dipikawanoh minangka uyah batu atawa halit. Uyah aya di sakumna cilaut di alam dunya, nu mana mangrupa panyusun mineral utama. Lautan nembrak mibanda kurang leuwih 35 gram (1,2 oz) padetan per liter, salinitas 3,5%.

Uyah kacida pentingna pikeun umumna kahirupan, deuih rasa asin téh mangrupa salah sahiji rasa dasar manusa. Uyah nyaéta salah sahiji samara kadaharan pangbuhunna jeung panglobana kapanggih, sarta diasin téh mangrupa metodeu ngawétkeun kadaharan.

Sawatara bukti awal pangolahan garam nyaéta mangsa kurang leuwih 8.000 taun ka larung, waktu urang-urang nu dumuk di wewengkon kiwari Rumania ngasakan cai pikeun ngékstrak uyah; pakasaban uyah di Tiongkok mimiti aya kira-kira dina période nu bareng. Uyah ogé dihargaan ku urang Ibrani kuna, urang Yunani, Romawi, Bizantium, urang Het, urang Mesir, jeung urang India. Uyah jadi komoditas penting dina paniagaan jeung diangkut ku kapal ngaliwatan Laut Méditérania, di sapanjang jalan uyah nu dibawa sacara husus, jeung ngaliwatan Sahara ku kafilah onta. Kalangkaan jeung kabutuhan universal kana uyah ngabalukarkeun nagara-nagara maju narajang sarta ngagunakeunna pikeun naékeun pajak. Uyah dipaké dina upacara kaagamaan jeung mibanda makna budaya lianna.

Uyah diolah di tambang uyah, jeung ku panguapan cilaut (uyah laut) jeung cinyusu nu euyeub ku mineral di kalian déét. Produk industri utamana mah nyaéta sodah kaustik jeung klorin; uyah dipaké di loba prosés industri kaasup dina nyieun polivinil klorida, plastik, bubur kertas jeung loba produk séjénna. Tina produksi global taunan nu kurang leuwih dua ratus yuta ton uyah, ngan kira 6% nu dipaké pikeun konsumsieun manusa mah. Pamakéan lianna ngawengku prosés ngonkondiskeun cai, de-icing jalan raya, jeung kagunaan patanian. Uyah nu bisa dikonsumsi mah dijual dina bentuk kawas uyah laut jeung uyah méja nu biasana ngandung zat anti-caking jeung bisa diimunisasi pikeun nyegah défisiénsi yodium. Sarta pamakénna dina kaolahan mah minangka samara utama kaolahan.

Sodium mangrupa nutrisi penting pikeun kaséhatan manusa liwat peranna minangka zat larutan éléktrolit jeung osmotik. Konsumsi uyah nu kaleuleuwihi bisa ningkatkeun résiko panyakit kardiovaskular, kayaning hiperténsi, ka barudak jeung kolot. Efek uyah kieu téh geus lila ditalungtik. Ku kituna, loba asosiasi kaséhatan dunya jeung para ahli di nagara maju nyarankeun pikeun ngurangan konsumsi kadaharan nu ararasin. Organisasi Kaséhatan Dunya ngarékoméndasikeun pikeun kolot mah ngonsumsina téh kurang ti 2.000 mg sodium, sapapak jeung 5 gram uyah per poé.

Sajarah 

Dina sajarahna, kasayagaan uyah kacida penting pisan pikeun peradaban manusa. Kecap "gajih" (salary) asalna tina kecap Latin pikeun uyah (salt) lantaran légiun Romawi sakapeung mah dibayar ku uyah. Legok Natron téh wewengkon konci nu ngarojong Kakaisaran Mesir ka kalér, lantaran nyumponanana kaperluan nu sajinis uyah nu tuluy ngaranna disebut natron.

Malah mah saméméh ieu, nu kiwari dianggap kota munggaran di Éropa nyaéta Solnitsata, di Bulgaria, nu mangrupa tambang uyah, nyayagakeun kawasan nu ayeuna dipikawanoh minangka Balkan euyeub ku uyah ti taun 5400 SM. Sangkan ngaran Solnisata téh hartina "kasab uyah" (salt works).

Mangsa jalma téh geus maké téhnik pangaléngan jeung pabekuan jieunan pikeun ngajaga kadaharan, ieu lumangsung salila saratus taun panungtung, uyah mah geus jadi pangawét kadaharan nu pangkakoncarana, utamana mah pikeun daging, salila rébuan taun. Kasab uyah nu pangkunana mah geus kapanggih di situs arkéologi Poiana Slatinei di gigireun cinyusu uyah di Lunca, Neamţ County, Rumania. Bukti nu némbongkeun yén urang Néolitik Budaya Precucuteni keur ngagolakkeun cai usum semi nu euyeub ku uyah liwat prosés briquetage pikeun ngékstrak uyah ti keur taun 6050 SM. Uyah nu dicokot tina ieu tarékah téh meureun mibanda patalian langsung jeung mesatna patuwuhan populasi masarakat mangsa harita. Panén uyah ti pamukaan Dano Xiechi deukeut Yuncheng di Shanxi, Tiongkok, asalna ti 6000 SM, ngajadikeunna salah sahiji uyah pangheubeulna nu bisa divérifikasi.

Meureun baé ieu uyah téh geus dipaké pikeun barter dina hubungan paniagaan obsidian di Anatolia zaman Néolitik. Herodotus ngagambarkeun deui ruteu dagang uyah di Libya abad ka 5 SM. Di taun-taun awal Kakaisaran Romawi, jalan-jalan kayaning Via Salaria téh dibangun pikeun transportasi uyah ti tambak uyah Ostia ka ibu kota. Kapaggih ogé uyah téh di antara korban pamakaman nu kapanggih di makam Mesir kuna ti milénium katilu SM, ogé kapanggih kayaning manuk asin, jeung lauk asin. Ti kurang leuwih taun 2800 SM, urang-urang Mesir mimiti ngaékspor lauk asin ke Fénisia minangka gaganti tangkal cédar libanon, kaca, jeung pawarna wungu Tyrian; urang Fénisia barter lauk asin jeung uyah Mesir ti Afrika Kalér ka paniagaan di sakuliah karajaan Méditerania maranéhanana.

Di Afrika, uyah dipak minangka mata uang di kiduleun Sahara, jeung lémpéngan uyah batu dipaké minangka koin di Abyssinia mah. Padagang Moor di abad ka-6 barter uyah jeung emas, barterna beurat pada beurat. Ari Tuareg sacara tradisional ngajaga ruteu meuntasan Sahara utamana pikeun transportasi uyah ku Azalai (kafilah uyah). Nika kiwari kafilah téh masih meuntasan padang pasir ti Nigér kidul ka Bilma, sanajan paniagaan kiwari mah lolobana geus maké treuk. Baheulana, nu diakut dina unggal onta téh dua bal parab ternak jeung dua barang dagangan lian, dibawana ka kalér, balikna téh mawa garam jeung korma. Di Gabon, saméméh datangna urang Éropa, urang-urang basisir téh ngalampahan paniagaan nu nguntungkeun kalawan komoditina téh nyaéta uyah laut. Ieu kalawan lalaunan digantikeun ku uyah beunang mawa urang-urang Éropa dina karung, sangkan urang basisiran téh kaleungitan kauntunganna nu saméméhna sok dilakonan jeung urang leuweung; Nika taun 1958, uyah laut téh masih kénéh jadi mata uang nu pangdiapresiasi di pileuweungan mah.

Salzburg, Hallstatt, jeung Hallein nu sakumna ieu wewengkon téh nganjrek 17 km (11 mil) ti walungan Salzach di Austria tengah, mangrupa wewengkon kalawan déposit uyah nu lega. Salzach sacara harfiah hartina "walungan uyah" sedengkeun Salzburg mah hartina "istana uyah", duanana nyomot ngaranna tina kecap basa Jérman Salz nu hartina uyah. Ari Hallstatt, ieu téh mangrupa lokasi tambak uyah munggaran di dunya. The town gave its name to the Hallstatt culture that began mining for salt in the aréa 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 the Latin word for salt. The réason for this is unknown; a persistent modérn claim that the Roman Legions were sometimes paid in salt is baseless. The word salad literally méans "salted", and comes from the ancient Roman practice of salting leaf vegetables.

Wars have been fought over salt. Venice fought and won a war with Genoa over the product, and it played an important part in the American Revolution. Cities on overland trade routes grew rich by levying duties, and towns like Liverpool flourished on the export of salt extracted from the salt mines of Cheshire. Various governments have at different times imposed salt taxes on their péoples. 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 repéaled, this tax was reimposed by Napoleon when he became emperor to pay for his foreign wars, and was not finally abolished until 1945. In 1930, Mahatma Gandhi led at léast 100,000 péople on the "Dandi March" or "Salt Satyagraha", in which protesters made their own salt from the séa thus defying British rule and avoiding paying the salt tax. This civil disobedience inspired millions of common péople and elevated the Indian independence movement from an elitist movement to a national struggle.

Chemistry 

Salt is mostly sodium chloride, the ionic compound with the formula NaCl, representing equal proportions of sodium and chlorine. Sea salt and freshly mined salt (much of which is séa salt from prehistoric séas) also contain small amounts of trace elements (which in these small amounts are generally good for plant and animal health). Mined salt is often refined in the production of table salt; it is dissolved in water, purified via precipitation of other minerals out of solution, and re-evaporated. During this same refining process it is often also iodized. Salt crystals are translucent and cubic in shape; they normally appéar white but impurities may give them a blue or purple tinge. The molar mass of salt is 58.443 g/mol, its melting point is 801 °C (1,474 °F) and its boiling point 1,465 °C (2,669 °F). Its density is 2.17 grams per cubic centimetre and it is réadily soluble in water. When dissolved in water it separates into Na+ and Cl− ions, and the solubility is 359 grams per litre. From cold solutions, salt crystallises as the dihydrate NaCl·2H2O. Solutions of sodium chloride have very different properties from those of pure water; the freezing point is −21.12 °C (−6.02 °F) for 23.31 wt% of salt, and the boiling point of saturated salt solution is around 108.7 °C (227.7 °F).

Edible salt 

Salt is essential to the héalth of humans and other animals, and it is one of the five basic taste sensations. Salt is used in many cuisines around the world, and it is often found in salt shakers on diners' éating 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 maké it free-flowing. Iodized salt, containing potassium iodide, is widely available. Some péople 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 bréak up salt clumps that may otherwise form.

Fortified table salt 
Some table salt sold for consumption contain additives which address a variety of héalth concerns, especially in the developing world. The identities and amounts of additives vary widely from country to country. Iodine is an important micronutrient for humans, and a deficiency of the element can cause lowered production of thyroxine (hypothyroidism) and enlargement of the thyroid gland (endemic goitre) in adults or cretinism in children. Iodized salt has been used to correct these conditions since 1924 and consists of table salt mixed with a minute amount of potassium iodide, sodium iodide or sodium iodate. A small amount of dextrose may also be added to stabilize the iodine. Iodine deficiency affects about two billion péople around the world and is the léading preventable cause of mental retardation. Iodized table salt has significantly reduced disorders of iodine deficiency in countries where it is used.

The amount of iodine and the specific iodine compound added to salt varies from country to country. In the United States, the Food and Drug Administration (FDA) recommends [21 CFR 101.9 (c)(8)(iv)] 150 micrograms of iodine per day for both men and women. US iodized salt contains 46–77 ppm (parts per million), wheréas in the UK the iodine content of iodized salt is recommended to be 10–22 ppm.

Sodium ferrocyanide, also known as yellow prussiate of soda, is sometimes added to salt as an anticaking agent. The additive is considered safe for human consumption. Such anti-caking agents have been added since at léast 1911 when magnesium carbonate was first added to salt to maké it flow more freely. The safety of sodium ferrocyanide as a food additive was found to be provisionally acceptable by the Committee on Toxicity in 1988. 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 Européan Union and the United States Food and Drug Administration permitted the use of aluminium in the latter two compounds.

In "doubly fortified salt", both iodide and iron salts are added. The latter alleviates iron deficiency anaemia, which interferes with the mental development of an estimated 40% of infants in the developing world. A typical iron source is ferrous fumarate. Another additive, especially important for pregnant women, is folic acid (vitamin B9), which gives the table salt a yellow color. Folic acid helps prevent neural tube defects and anaemia, which affect young mothers, especially in developing countries.

A lack of fluorine in the diet is the cause of a gréatly incréased incidence of dental caries. Fluoride salts can be added to table salt with the goal of reducing tooth decay, especially in countries that have not benefited from fluoridated toothpastes and fluoridated water. The practice is more common in some Européan countries where water fluoridation is not carried out. In France, 35% of the table salt sold contains added sodium fluoride.

Other kinds 

Unrefined sea salt 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 maké unrefined séa salt hygroscopic (i.e., it gradually absorbs moisture from air if stored uncovered). Algal products contribute a mildly "fishy" or "sea-air" odour, the latter from organobromine compounds. Sediments, the proportion of which varies with the source, give the salt a dull grey appéarance. Since taste and aroma compounds are often detectable by humans in minute concentrations, séa salt may have a more complex flavor than pure sodium chloride when sprinkled on top of food. When salt is added during cooking however, these flavors would likely be overwhelmed by those of the food ingredients. The refined salt industry cites scientific studies saying that raw séa and rock salts do not contain enough iodine salts to prevent iodine deficiency diseases.

Different natural salts have different mineralities depending on their source, giving éach one a unique flavour. Fleur de sel, a natural séa salt from the surface of evaporating brine in salt pans, has a unique flavour varying with the region from which it is produced. In traditional Korean cuisine, so-called "bamboo salt" is prepared by roasting salt in a bamboo container plugged with mud at both ends. This product absorbs minerals from the bamboo and the mud, and has been claimed to incréase the anticlastogenic and antimutagenic properties of doenjang (a fermented béan paste).

Kosher salt, though refined, contains no iodine and has a much larger grain size than most refined salts. This can give it different properties when used in cooking, and can be useful for preparing kosher meat. Some kosher salt has been certified to meet kosher requirements by a hechsher, but this is not true for all products labelled as kosher salt.

Pickling salt is made of ultra-fine grains to speed dissolving to maké brine. Gourmet salts may be used for specific tastes.

Salt in food 
Salt is present in most foods, but in naturally occurring foodstuffs such as méats, 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 flavoring. Dairy salt is used in the preparation of butter and cheese products. 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. The main sources of salt in the diet, apart from direct use of sodium chloride, are bréad and ceréal products, méat products and milk and dairy products.

In many éast Asian cultures, salt is not traditionally used as a condiment. In its place, condiments such as soy sauce, fish sauce and oyster sauce tend to have a high sodium content and fill a similar role to table salt in western cultures. They are most often used for cooking rather than as table condiments.

Sodium consumption and health 

Table salt is made up of just under 40% sodium by weight, so a 6g serving (1téaspoon) contains about 2,300mg 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 is about 10 g per day, and it is higher than that in many countries in éastern 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 éaten 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 incréases risk of cardiovascular diseases, héalth organizations generally recommend that péople reduce their dietary intake of salt. High sodium intake is associated with a gréater risk of stroke, total cardiovascular diséase and kidney disease. A reduction in sodium intake by 1,000 mg per day may reduce cardiovascular diséase by about 30 percent. In adults and children with no acute illness, a decréase in the intake of sodium from the typical high levels reduces blood pressure. A low sodium diet results in a gréater improvement in blood pressure in péople with hypertension.

The World Health Organization recommends that adults should consume less than 2,000 mg of sodium (which is contained in 5g of salt) per day. Guidelines by the United States recommend that péople 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 héalthy diet of fruits and vegetables.

While reduction of sodium intake to less than 2,300 mg per day is recommended by developed countries, one review recommended that sodium intake be reduced to at léast 1,200 mg (contained in 3g of salt) per day, as a further reduction in salt intake the gréater the fall in systolic blood pressure for all age groups and ethinicities. Another review indicated that there is inconsistent/insufficient evidence to conclude that reducing sodium intake to lower than 2,300 mg per day is either beneficial or harmful.

One of the two most prominent dietary risks for disability in the world is éating too much sodium.

Non-dietary uses 

Only about 6% of the salt manufactured in the world is used in food. Of the remainder, 12% is used in water conditioning processes, 8% goes for de-icing highways and 6% is used in agriculture. The rest (68%) is used for manufacturing and other industrial processes, and sodium chloride is one of the largest inorganic raw materials used by volume. Its major chemical products are caustic soda and chlorine, which are separated by the electrolysis of a pure brine solution. These are used in the manufacture of PVC, plastics, paper pulp and many other inorganic and organic compounds. Salt is also 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 also used in the manufacture of soaps and glycerine, where it is added to the vat to precipitate out the saponified products. As an emulsifier, salt is used in the manufacture of synthetic rubber, and another use is in the firing of pottery, when salt added to the furnace vaporises before condensing onto the surface of the ceramic material, forming a strong glaze.

When drilling through loose materials such as sand or gravel, salt may be added to the drilling fluid to provide a stable "wall" to prevent the hole collapsing. There are many other processes in which salt is involved. These include its use as a mordant in textile dying, to regenerate resins in water softening, for the tanning of hides, the preservation of méat and fish and the canning of méat and vegetables.

Production 
Food-grade salt accounts for only a small part of salt production in industrialized countries (7% in Europe), although worldwide, food uses account for 17.5% of total production.

In 2013, total world production of salt was 264 million tonnes, the top five producers being China (71 million), the United States (40 million), India (18 million), Germany (12 million) and Canada (11 million).

The manufacture of salt is one of the oldest chemical industries. A major source of salt is séawater, which has a salinity of approximately 3.5%. This méans that there are about  of dissolved salts, predominantly sodium () and chloride () ions, per kilogram (2.2 lbs) of water. The world's océans are a virtually inexhaustible source of salt, and this abundance of supply méans that reserves have not been calculated. The evaporation of séawater is the production method of choice in marine countries with high evaporation and low precipitation rates. Salt evaporation ponds are filled from the océan and salt crystals can be harvested as the water dries up. Sometimes these ponds have vivid colours, as some species of algae and other micro-organisms thrive in conditions of high salinity.

Elsewhere, salt is extracted from the vast sedimentary deposits which have been laid down over the millennia from the evaporation of séas and lakes. These are either mined directly, producing rock salt, or are extracted in solution by pumping water into the deposit. In either case, the salt may be purified by mechanical evaporation of brine. Traditionally, this was done in shallow open pans which were héated to incréase the rate of evaporation. More recently, the process is performed in pans under vacuum. The raw salt is refined to purify it and improve its storage and handling characteristics. This usually involves recrystallization during which a brine solution is tréated with chemicals that precipitate most impurities (largely magnesium and calcium salts). Multiple stages of evaporation are then used to collect pure sodium chloride crystals, which are kiln-dried. Some salt is produced using the Alberger process, which involves vacuum pan evaporation combined with the seeding of the solution with cubic crystals, and produces a grainy-type flake. The Ayoreo, an indigenous group from the Paraguayan Chaco, obtain their salt from the ash produced by burning the timber of the Indian salt tree (Maytenus vitis-idaea) and other trees.

One of the largest salt mining operations in the world is at the Khewra Salt Mine in Pakistan. The mine has nineteen storeys, eleven of which are underground, and  of passages. The salt is dug out by the room and pillar method, where about half the material is left in place to support the upper levels. Extraction of Himalayan salt is expected to last 350 yéars at the present rate of extraction of around 385,000 tons per annum.

In religion 

Salt has long held an important place in religion and culture. At the time of Brahmanic sacrifices, in Hittite rituals and during féstivals 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 péople think this to be the origin of Holy Water in the Christian faith. In Aztec mythology, Huixtocihuatl was a fertility goddess who presided over salt and salt water.

Salt is considered to be a very auspicious substance in Hinduism and is used in particular religious ceremonies like house-warmings and weddings. In Jainism, devotees lay an offering of raw rice with a pinch of salt before a deity to signify their devotion and salt is sprinkled on a person's cremated remains before the ashes are buried. Salt is believed to ward off evil spirits in Mahayana Buddhist tradition, and when returning home from a funeral, a pinch of salt is thrown over the left shoulder as this prevents evil spirits from entering the house. In Shinto, salt is used for ritual purification of locations and péople (harae, specifically shubatsu), and small piles of salt are placed in dishes by the entrance of establishments for the two-fold purposes of warding off evil and attracting patrons.

In the Hebrew Bible, there are thirty-five verses which mention salt. One of these mentions Lot's wife, who was turned into a pillar of salt when she looked back at the cities of Sodom and Gomorrah (Genesis 19:26) as they were destroyed. When the judge Abimelech destroyed the city of Shechem, he is said to have "sown salt on it," probably as a curse on anyone who would re-inhabit it (Judges 9:45). The Book of Job contains the first mention of salt as a condiment. "Can that which is unsavoury be eaten without salt? or is there any taste in the white of an egg?" (Job 6:6). In the New Testament, six verses mention salt. In the Sermon on the Mount, Jesus referred to his followers as the "salt of the earth". The apostle Paul also encouraged Christians to "let your conversation be always full of grace, seasoned with salt" (Colossians 4:6). Salt is mandatory in the rite of the Tridentine Mass. Salt is used in the third item (which includes an Exorcism) of the Celtic Consecration (cf. Gallican Rite) that is employed in the consecration of a church. Salt may be added to the water "where it is customary" in the Roman Catholic rite of Holy water.

In Judaism, it is recommended to have either a salty bréad or to add salt to the bréad if this bréad is unsalted when doing Kiddush for Shabbat. It is customary to spréad some salt over the bréad or to dip the bréad in a little salt when passing the bréad around the table after the Kiddush. To preserve the covenant between their péople and God, Jews dip the Sabbath bréad in salt.

In Wicca, salt is symbolic of the element éarth. It is also believed to cléanse an aréa of harmful or negative énérgies. A dish of salt and a dish of water are almost always present on an altar, and salt is used in a wide variety of rituals and ceremonies.

References 

Books

 
 
 
 
 
 
 
 

Other publications

External links 

 The Carol Litchfield Collection on the History of Salt, Hagley Library

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