Editing Brine (section)

==Composition and purification==
Brine consists of concentrated solution of Na<sup>+</sup> and Cl<sup>−</sup> ions.   Other cations found in various brines include K<sup>+</sup>, Mg<sup>2+</sup>, Ca<sup>2+</sup>, and Sr<sup>2+</sup>.  The latter three are problematic because they form scale and they react with soaps.  Aside from chloride, brines sometimes contain Br<sup>−</sup> and I<sup>−</sup> and, most problematically, sulfate {{chem|SO|4|2−}}.  Purification steps often include the addition of calcium oxide to precipitate solid [[magnesium hydroxide]] together with gypsum (CaSO<sub>4</sub>), which can be removed by filtration.  Further purification is achieved by [[Fractional crystallization (chemistry)|fractional crystallization]].  The resulting purified salt is called '''evaporated salt''' or '''vacuum salt'''.<ref name=Ullmann>{{Ullmann |doi=10.1002/14356007.a24_317.pub4|title=Sodium Chloride|year=2010|last1=Westphal|first1=Gisbert|last2=Kristen|first2=Gerhard|last3=Wegener|first3=Wilhelm|last4=Ambatiello|first4=Peter|last5=Geyer|first5=Helmut|last6=Epron|first6=Bernard|last7=Bonal|first7=Christian|last8=Steinhauser|first8=Georg|last9=Götzfried|first9=Franz|isbn=978-3527306732}}</ref>