Sal común: Diferenzas entre revisións
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Liña 33:
==Produción==
[[Ficheiro:Bo Kluea 01.jpg|thumb|Produción de sal en [[Bo Kluea]], [[Tailandia]]]]
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O sal destinado para a alimentación representa só unha pequena parte da produción de sal nos países industrializados (un 7% en Europa),<ref>{{cite web | url=http://eusalt.com/salt-uses | title=Salt Uses | publisher=European Salt Producers' Association | accessdate=5 de maio de 2015}}</ref> aínda que no conxunto global a produción para alimentación é dun 17,5% do total.<ref>{{cite web | url=http://www.roskill.com/reports/salt | title=Roskill Information Services | publisher=Roskill.com | date=30 de marzo de 2011 | accessdate=7 de xullo de 2011}}</ref> No ano 2013 a produción mundial total foi de 264 millóns de toneladas. Os cinco principais produtores foron [[China]] (71 millóns), os [[Estados Unidos]] (40 millóns), [[India]] (18 millóns), [[Alemaña]] (12 millóns) e [[Canadá]] (11 millóns).<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=2014 | accessdate=8 de xuño de 2016}}</ref>
▲| image2 = Piles of Salt Salar de Uyuni Bolivia Luca Galuzzi 2006 a.jpg
A manufactura do sal é unha das industrias químicas máis antigas.<ref>{{cite web | url=http://www.salt.org.il/arch.html | title=Salt made the world go round | work=Salt.org.il | date=1 de setembro de 1997 | accessdate=7 de xullo de 2011}}</ref> Unha das principais fontes de sal é a [[auga mariña]], que posúe unha [[salinidade]] dun 3,5%. Isto significa que hai uns 35 g de [[sal mariño|sales disoltas]], predominantemente [[ión]]s de [[sodio]] ({{chem|Na||+}}) e [[cloro]] ({{chem|Cl||-}}), por quilogramo de auga.<ref>{{Cite journal | last1 = Millero | first1 = F. J. | last2 = Feistel | first2 = R. | last3 = Wright | first3 = D. G. | last4 = McDougall | first4 = T. J. | title = The composition of Standard Seawater and the definition of the Reference-Composition Salinity Scale | doi = 10.1016/j.dsr.2007.10.001 | journal = Deep Sea Research Part I: Oceanographic Research Papers | volume = 55 | pages = 50 | year = 2008 }}</ref> Os [[océano]]s representan unha fonte virtualmente inesgotable de sal, e por mor desta abundancia de subministración non se ten calculado con exactitude o número de reservas dispoñible.<ref name=IHS/> A [[evaporación]] de auga mariña é o método de produción máis habitual nos países costeiros con baixos niveis de [[Precipitación (meteoroloxía)|precipitacións]].<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>
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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}}
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