Sodium Chloride
<p ><a href="http://en.wikipedia.org/wiki/Refining" title="Refining" >Refined</a> salt, which is most widely used presently, is mainly sodium chloride. Food grade salt accounts for only a small part of salt production in <a href="http://en.wikipedia.org/wiki/Developed_country" title="Developed country" >industrialized countries</a> (3 percent in Europe)<sup id="cite_ref-18" class="reference" ><a href="http://en.wikipedia.org/wiki/Salt#cite_note-18" >[19]</a></sup>although worldwide, food uses account for 17.5 percent of salt production.<sup id="cite_ref-19" class="reference" ><a href="http://en.wikipedia.org/wiki/Salt#cite_note-19" >[20]</a></sup>
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The majority is sold for industrial use. Salt has great commercial value because it is a necessary ingredient in many manufacturing processes. A few common examples include: the production of pulp and paper, setting dyes in textiles and fabrics, and the making of soaps and detergents.</p>
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The manufacture and use of salt is one of the oldest chemical industries.<sup id="cite_ref-20" class="reference" ><a href="http://en.wikipedia.org/wiki/Salt#cite_note-20" >[21]</a></sup> Salt can be obtained by evaporation of <a href="http://en.wikipedia.org/wiki/Sea_water" title="Sea water" class="mw-redirect" >sea water</a>, usually in shallow basins warmed by <a href="http://en.wikipedia.org/wiki/Sunlight" title="Sunlight" >sunlight</a>;<sup id="cite_ref-21" class="reference" ><a href="http://en.wikipedia.org/wiki/Salt#cite_note-21" >[22]</a></sup> salt so obtained was formerly called bay salt, and is now often called sea salt or solar salt. Rock salt deposits are formed by the evaporation of ancient salt lakes,<sup id="cite_ref-22" class="reference" ><a href="http://en.wikipedia.org/wiki/Salt#cite_note-22" >[23]</a></sup>and may be <a href="http://en.wikipedia.org/wiki/Mining" title="Mining" >mined</a> conventionally or through the injection of water. Injected water dissolves the salt, and the<a href="http://en.wikipedia.org/wiki/Brine" title="Brine" >brine</a> solution can be pumped to the surface where the salt is collectedAfter the raw salt is obtained, it is refined to purify it and improve its storage and handling characteristics. </p>
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Purification usually involves recrystallization. In recrystallization, a brine solution is treated with chemicals that precipitate most impurities (largely magnesium and calcium salts).<sup id="cite_ref-23" class="reference" ><a href="http://en.wikipedia.org/wiki/Salt#cite_note-23" >[24]</a></sup> Multiple stages of evaporation are then used to collect pure sodium chloride crystals, which are<a href="http://en.wikipedia.org/wiki/Kiln" title="Kiln" >kiln</a>-dried.</p>