Editing Chloralkali process (section)

===Membrane cell===
The most common chloralkali process involves the electrolysis of [[aqueous]] [[sodium chloride]] (a [[brine]]) in a [[Sodium hydroxide#Production|membrane cell]]. A membrane, such as [[Nafion#Chlor-alkali production cell membrane|Nafion]], Flemion or Aciplex, is used to prevent the reaction between the chlorine and hydroxide ions.

[[Image:Chloralkali_membrane.svg|thumb|center|upright=3|Basic membrane cell used in the [[electrolysis]] of brine. At the anode ('''A'''), chloride (Cl<sup>−</sup>) is oxidized to chlorine. The ion-selective membrane ('''B''') allows the counterion Na+ to freely flow across, but prevents anions such as hydroxide (OH<sup>−</sup>) and chloride from diffusing across. At the cathode ('''C'''), water is reduced to hydroxide and hydrogen gas. The net process is the electrolysis of an aqueous solution of NaCl into industrially useful products sodium hydroxide (NaOH) and chlorine gas.]]

Saturated brine is passed into the first chamber of the cell. Due to the higher concentration of chloride ions in the brine, the [[chloride]] ions are [[redox|oxidised]] at the [[anode]], losing electrons to become [[chlorine]] gas ('''A''' in figure):
:2Cl<sup>−</sup> → {{chem|Cl|2}} + 2[[electron|e<sup>−</sup>]]

At the [[cathode]], positive [[hydrogen ion]]s pulled from water molecules are [[redox|reduced]] by the electrons provided by the electrolytic current, to hydrogen gas, releasing [[hydroxide]] ions into the solution ('''C''' in figure):
:2{{chem|H|2|O}} + 2e<sup>−</sup> → H<sub>2</sub> + 2OH<sup>−</sup>

The ion-permeable [[ion-exchange membrane]] at the center of the cell allows only the [[sodium]] ions (Na<sup>+</sup>) to pass to the second chamber where they react with the hydroxide ions to produce [[caustic soda]] (NaOH) ('''B''' in figure):<ref name = Du/> 

Na<sup>+</sup> + OH<sup>−</sup> → NaOH

The overall reaction for the electrolysis of brine is thus:
:2NaCl + 2{{chem|H|2|O}} → {{chem|Cl|2}} + {{chem|H|2}} + 2NaOH