Sal común: Diferenzas entre revisións
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Liña 31:
{{AP|Cloruro de sodio}}
O sal é na súa maioría [[cloruro de sodio]], un [[composto químico]] de [[fórmula química|fórmula]] NaCl, que presenta unha proporción igual de [[sodio]] e [[cloro]]. O [[sal mairño]] e o sal recentemente minado tamén coneñen trazas doutros elementos. O sal extraído das minas adoita refinarse durante a produción do sal comestible, disolvéndose en [[auga]], purificándose por medio dun [[precipitado (química)|precipitado]] e dunha re-evaporación. Durante este mesmo proceso de refinamento adoita [[iodo|iodarse]]. Os cristais de sal son translúcidos e de forma [[cubo|cúbica]]. Teñen unha cor branca, pero poden ter impurezas que lles dan unha tintura azul ou púrpura. A [[masa molar]] do sal é 58,443 g/mol, o seu [[punto de fusión]] é 801 °C e o seu [[punto de ebulición]] é 1465 °C. A súa [[densidade]] é 2,17 gramos/cm<sup>3</sup> e é soluble á auga. Cando se disolve na auga sepárase en [[ión]]s Na<sup>+</sup> e Cl<sup>−</sup>, e a súa solubilidade é de 359 g/l.<ref name="EB"/> Partindo de solucións frías, o sal cristaliza en forma de dihidrato NaCl·2H<sub>2</sub>O. As solucións de cloruro de sodio teñen propiedades moi diferentes das da auga pura. O [[punto de conxelación]] é de −21,12 °C por 23,31 de [[fracción de masa]] de sal, e o punto de fusión dunha solución saturada de sal é duns 108,7 °C.<ref name=u1>{{cita libro|apelidos1=Elvers|nome1=B.|apelidos2=''et al.''|ano=1991|título=Ullmann's Encyclopedia of Industrial Chemistry|edición=5ª|volume=A24|editorial=Wiley|p=319|ISBN=978-3-527-20124-2}}</ref>
==Produción==▼
<!-- ▼
Food grade salt accounts for only a small part of salt production in [[Developed country|industrialized countries]] (7% in Europe),<ref>{{cite web | url=http://eusalt.com/salt-uses | title=Salt Uses | publisher=European Salt Producers' Association | accessdate=5 May 2015}}</ref> although worldwide, food uses account for 17.5% of total production.<ref>{{cite web | url=http://www.roskill.com/reports/salt | title=Roskill Information Services | publisher=Roskill.com | date=30 March 2011 | accessdate=7 July 2011}}</ref>▼
In 2013, total world production of salt was 264 million [[tonne]]s, the top five producers being China (71 million), the United States (40 million), India (18 million), Germany (12 million) and Canada (11 million).<ref>{{cite web | url=http://minerals.usgs.gov/minerals/pubs/commodity/salt/mcs-2014-salt.pdf | title=Salt | publisher=US Geological Survey, Mineral Commodity Summaries | date=February 2014 | accessdate=8 June 2016}}</ref>▼
{{multiple image|total_width=300|direction=vertical▼
| image1 = Bo Kluea 01.jpg▼
| width1 = 2500▼
| height1 = 1737▼
| caption1 = [[Brine]] from [[salt wells]] is boiled to produce salt at [[Bo Kluea District|Bo Kluea]], [[Nan Province]], Thailand▼
| image2 = Piles of Salt Salar de Uyuni Bolivia Luca Galuzzi 2006 a.jpg▼
| width2 = 2000▼
| height2 = 1320▼
| caption2 = Salt mounds in [[Salar de Uyuni]], Bolivia▼
}}▼
The manufacture of salt is one of the oldest chemical industries.<ref>{{cite web | url=http://www.salt.org.il/arch.html | title=Salt made the world go round | work=Salt.org.il | date=1 September 1997 | accessdate=7 July 2011}}</ref> A major source of salt is seawater, which has a [[salinity]] of approximately 3.5%. This means that there are about {{convert|35|g|oz}} of [[sea salt|dissolved salts]], predominantly [[sodium]] ({{chem|Na||+}}) and [[chloride]] ({{chem|Cl||-}}) [[ions]], per kilogram (2.2 lbs) of water.{{sfn|Millero|Feistel|Wright|McDougall|2008}} The world's oceans are a virtually inexhaustible source of salt, and this abundance of supply means that reserves have not been calculated.<ref name=IHS/> The evaporation of seawater is the production method of choice in marine countries with high evaporation and low precipitation rates. [[Salt evaporation pond]]s are filled from the ocean and salt crystals can be harvested as the water dries up. Sometimes these ponds have vivid colours, as some species of algae and other micro-organisms thrive in conditions of high salinity.<ref>{{cite web | url = http://visibleearth.nasa.gov/view.php?id=2631 | title = Salt Ponds, South San Francisco Bay |work= NASA Visible Earth |publisher=NASA |accessdate=5 May 2015}}</ref>▼
Elsewhere, salt is extracted from the vast sedimentary deposits which have been laid down over the millennia from the evaporation of seas and lakes. These are either [[salt mine|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 [[Open pan salt making|shallow open pans]] which were heated to increase the rate of evaporation. More recently, the process is performed in pans under [[vacuum]].{{sfn|Kostick|2011}} 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 treated 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.<ref>[http://web.archive.org/web/20090409144219/http://www.saltsense.co.uk/aboutsalt-prod02.htm About salt: Production]. The Salt Manufacturers Association</ref> 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.<ref>{{cite web |url=http://www.britannica.com/EBchecked/topic/12642/Alberger-process |title=Alberger process |work=Manufacture of salt: Uses of artificial heat |publisher=Encyclopædia Britannica online |accessdate=9 October 2013}}</ref> The [[Ayoreo people|Ayoreo]], an indigenous group from the Paraguayan [[Gran Chaco people|Chaco]], obtain their salt from the ash produced by burning the timber of the Indian salt tree (''Maytenus vitis-idaea'') and other trees.{{sfn|Schmeda-Hirschmann|1994}}▼
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 {{convert|400|km|abbr=on}} of passages. The salt is dug out by the [[room and pillar]] method, where about half the material is left in place to support the upper levels. Extraction of [[Himalayan salt]] is expected to last 350 years at the present rate of extraction of around 385,000 tons per annum.<ref name="The Seattle Times">{{cite news |last=Pennington |first=Matthew |title=Pakistan salt mined old-fashioned way mine|url=http://seattletimes.nwsource.com/html/nationworld/2002159747_saltmine25.html |accessdate=11 October 2013 |newspaper=The Seattle Times |date=25 January 2005}}</ref> -->▼
==Papel na alimentación==
Liña 65 ⟶ 88:
==Usos non alimentarios==
So un 6% do sal manufacturado no mundo utilízase como alimento. O 12% emprégase en procesos de acondicionamento de augas, o 8% para o desxeo de [[autoestrada]]s e o 6% na [[agricultura]]. O 68% restante utilízase en procesos de manufacturas e procesos industriais<ref>{{cite web |url=http://www.maldonsalt.co.uk/About-Salt-The-many-uses-of-Salt.html |title=The many uses of salt |publisher=Maldon Salt Company |accessdate=10 October 2013}}</ref> principalmente en forma de cloruro de sodio. O uso máis habitual é na produción de [[sosa cáustica]] e [[cloro]], separados por [[electrólise]] dunha solución pura de sal. A súa vez estes produtos empréganse na manufactura de [[policloruro de vinilo]], [[plástico]]s, [[celulosa]] e outros compostos orgánicos e inorgánicos. O sal utilízase tamén coma [[Fundición (industria)|fundente]] na produción de [[aluminio]], na manufactura de [[xabón]]s, [[glicerina]] e [[caucho sintético]] entre outros.<ref name=WASG>{{cite web |url=http://www.wasalt.com.au/SaltUses.html |title=Salt uses |publisher=WA Salt Group |accessdate=10 de outubro de 2013 |archiveurl= https://web.archive.org/web/20131011054052/http://www.wasalt.com.au/SaltUses.html |archivedate= 11 de outubro de 2013 }}</ref> A maiores destes usos o sal está involucrado noutros procesos, incluíndo o seu uso coma mordente na tintura de [[textil|textís]], na rexeneración de [[resina]]s, no [[curtido]] de peles, na preservación de carne e pescado e no [[envasado]] de carne e vexetais.<ref name=WASG/><ref name=IHS>{{cite web |url=http://www.ihs.com/products/chemical/planning/ceh/sodium-chloride.aspx |title=Sodium chloride |date=1 de decembro de 2008 |publisher=IHS Chemical |accessdate=12 de marzo de 2013}}</ref><ref>{{Cite web |last=Kostick |first=Dennis S. |url=http://minerals.usgs.gov/minerals/pubs/commodity/salt/myb1-2010-salt.pdf |title=Salt |date=1 November 2011 |work=2010 Minerals Yearbook |publisher=U.S. Geological Survey |accessdate=12 de marzo de 2013}}</ref>
▲==Produción==
▲<!--
▲Food grade salt accounts for only a small part of salt production in [[Developed country|industrialized countries]] (7% in Europe),<ref>{{cite web | url=http://eusalt.com/salt-uses | title=Salt Uses | publisher=European Salt Producers' Association | accessdate=5 May 2015}}</ref> although worldwide, food uses account for 17.5% of total production.<ref>{{cite web | url=http://www.roskill.com/reports/salt | title=Roskill Information Services | publisher=Roskill.com | date=30 March 2011 | accessdate=7 July 2011}}</ref>
▲In 2013, total world production of salt was 264 million [[tonne]]s, the top five producers being China (71 million), the United States (40 million), India (18 million), Germany (12 million) and Canada (11 million).<ref>{{cite web | url=http://minerals.usgs.gov/minerals/pubs/commodity/salt/mcs-2014-salt.pdf | title=Salt | publisher=US Geological Survey, Mineral Commodity Summaries | date=February 2014 | accessdate=8 June 2016}}</ref>
▲{{multiple image|total_width=300|direction=vertical
▲| image1 = Bo Kluea 01.jpg
▲| width1 = 2500
▲| height1 = 1737
▲| caption1 = [[Brine]] from [[salt wells]] is boiled to produce salt at [[Bo Kluea District|Bo Kluea]], [[Nan Province]], Thailand
▲| image2 = Piles of Salt Salar de Uyuni Bolivia Luca Galuzzi 2006 a.jpg
▲| width2 = 2000
▲| height2 = 1320
▲| caption2 = Salt mounds in [[Salar de Uyuni]], Bolivia
▲}}
▲The manufacture of salt is one of the oldest chemical industries.<ref>{{cite web | url=http://www.salt.org.il/arch.html | title=Salt made the world go round | work=Salt.org.il | date=1 September 1997 | accessdate=7 July 2011}}</ref> A major source of salt is seawater, which has a [[salinity]] of approximately 3.5%. This means that there are about {{convert|35|g|oz}} of [[sea salt|dissolved salts]], predominantly [[sodium]] ({{chem|Na||+}}) and [[chloride]] ({{chem|Cl||-}}) [[ions]], per kilogram (2.2 lbs) of water.{{sfn|Millero|Feistel|Wright|McDougall|2008}} The world's oceans are a virtually inexhaustible source of salt, and this abundance of supply means that reserves have not been calculated.<ref name=IHS/> The evaporation of seawater is the production method of choice in marine countries with high evaporation and low precipitation rates. [[Salt evaporation pond]]s are filled from the ocean and salt crystals can be harvested as the water dries up. Sometimes these ponds have vivid colours, as some species of algae and other micro-organisms thrive in conditions of high salinity.<ref>{{cite web | url = http://visibleearth.nasa.gov/view.php?id=2631 | title = Salt Ponds, South San Francisco Bay |work= NASA Visible Earth |publisher=NASA |accessdate=5 May 2015}}</ref>
▲Elsewhere, salt is extracted from the vast sedimentary deposits which have been laid down over the millennia from the evaporation of seas and lakes. These are either [[salt mine|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 [[Open pan salt making|shallow open pans]] which were heated to increase the rate of evaporation. More recently, the process is performed in pans under [[vacuum]].{{sfn|Kostick|2011}} 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 treated 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.<ref>[http://web.archive.org/web/20090409144219/http://www.saltsense.co.uk/aboutsalt-prod02.htm About salt: Production]. The Salt Manufacturers Association</ref> 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.<ref>{{cite web |url=http://www.britannica.com/EBchecked/topic/12642/Alberger-process |title=Alberger process |work=Manufacture of salt: Uses of artificial heat |publisher=Encyclopædia Britannica online |accessdate=9 October 2013}}</ref> The [[Ayoreo people|Ayoreo]], an indigenous group from the Paraguayan [[Gran Chaco people|Chaco]], obtain their salt from the ash produced by burning the timber of the Indian salt tree (''Maytenus vitis-idaea'') and other trees.{{sfn|Schmeda-Hirschmann|1994}}
▲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 {{convert|400|km|abbr=on}} of passages. The salt is dug out by the [[room and pillar]] method, where about half the material is left in place to support the upper levels. Extraction of [[Himalayan salt]] is expected to last 350 years at the present rate of extraction of around 385,000 tons per annum.<ref name="The Seattle Times">{{cite news |last=Pennington |first=Matthew |title=Pakistan salt mined old-fashioned way mine|url=http://seattletimes.nwsource.com/html/nationworld/2002159747_saltmine25.html |accessdate=11 October 2013 |newspaper=The Seattle Times |date=25 January 2005}}</ref> -->
==Papel na relixión==
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