Editing Reversible reaction (section)

== History ==

The concept of a reversible reaction was introduced by [[Claude Louis Berthollet]] in 1803, after he had observed the formation of [[sodium carbonate]] crystals at the edge of a [[salt lake]]<ref>[http://www.chem1.com/acad/webtext/chemeq/Eq-01.html#NAP How did Napoleon Bonaparte help discover reversible reactions?]. Chem<sub>1</sub> General Chemistry Virtual Textbook: Chemical Equilibrium Introduction: reactions that go both ways.</ref> (one of the [[natron]] lakes in Egypt, in [[limestone]]):

:2NaCl + CaCO<sub>3</sub> → Na<sub>2</sub>CO<sub>3</sub> + CaCl<sub>2</sub>

He recognized this as the reverse of the familiar reaction
: Na<sub>2</sub>CO<sub>3</sub> + CaCl<sub>2</sub>→ 2NaCl + CaCO<sub>3</sub>

Until then, [[chemical reaction]]s were thought to always proceed in one direction. Berthollet reasoned that the excess of [[salt]] in the lake helped push the "reverse" reaction towards the formation of sodium carbonate.<ref>Claude-Louis Berthollet,"Essai de statique chimique", Paris, 1803. [https://books.google.com/books?id=cKU5AAAAcAAJ&q=berthollet+essai (Google books)]</ref>

In 1864, [[Peter Waage]] and [[Cato Maximilian Guldberg]] formulated their [[law of mass action]] which quantified Berthollet's observation. Between 1884 and 1888, [[Henry Louis Le Chatelier|Le Chatelier]] and [[Karl Ferdinand Braun|Braun]] formulated [[Le Chatelier's principle]], which extended the same idea to a more general statement on the effects of factors other than concentration on the position of the equilibrium.