Editing Sodium carbonate (section)

===Solvay process===
{{Main|Solvay process}}

In 1861, the [[Belgium|Belgian]] industrial chemist [[Ernest Solvay]] developed a method for making sodium carbonate by first reacting [[sodium chloride]], [[ammonia]], water, and carbon dioxide to generate [[sodium bicarbonate]] and [[ammonium chloride]]:<ref name=Ullmann/>

{{block indent|NaCl + NH<sub>3</sub> + CO<sub>2</sub> + H<sub>2</sub>O → NaHCO<sub>3</sub> + NH<sub>4</sub>Cl}}

The resulting sodium bicarbonate was then converted to sodium carbonate by heating it, releasing water and carbon dioxide:

{{block indent|2NaHCO<sub>3</sub> → Na<sub>2</sub>CO<sub>3</sub> + H<sub>2</sub>O + CO<sub>2</sub>}}

Meanwhile, the ammonia was regenerated from the ammonium chloride byproduct by treating it with the lime ([[calcium oxide]]) left over from carbon dioxide generation:

{{block indent|2NH<sub>4</sub>Cl + CaO → 2NH<sub>3</sub> + CaCl<sub>2</sub> + H<sub>2</sub>O}}

The Solvay process recycles its ammonia. It consumes only brine and limestone, and [[calcium chloride]] is its only waste product. The process is substantially more economical than the Leblanc process, which generates two waste products, [[calcium sulfide]] and [[hydrogen chloride]]. The Solvay process quickly came to dominate sodium carbonate production worldwide. By 1900, 90% of sodium carbonate was produced by the Solvay process, and the last Leblanc process plant closed in the early 1920s.<ref name=Ullmann/>

The second step of the Solvay process, heating sodium bicarbonate, is used on a small scale by home cooks and in restaurants to make sodium carbonate for culinary purposes (including [[pretzels]] and [[alkali noodles]]). The method is appealing to such users because sodium bicarbonate is widely sold as baking soda, and the temperatures required ({{convert|250|F|C}} to {{convert|300|F|C}}) to convert baking soda to sodium carbonate are readily achieved in conventional kitchen [[oven]]s.<ref name="McGee"/>