Ammonia-soda Process

Also known as the Solvay Process.
An industrial method of making sodium carbonate from ammonium carbonate and sodium chloride. When carbon dioxide is passed into a nearly saturated solution of common salt containing ammonia, ammonium carbonate is formed and this tends to pass into ammonium hydrogencarbonate, which reacts with sodium chloride to form sodium hydrogencarbonate and ammonium chloride. Sodium hydrogencarbonate is sparingly soluble in a solution of sodium chloride or ammonium chloride, and mostly separates out as a solid which may be filtered off.

              2NH3   +   H2O   +   CO2   ==>   (NH4)2CO3
     (NH4)2CO3   +    H2O   +   CO2   ==>   2NH4HCO3
       NaCl   +   NH4HCO3  <==>  NaHCO3   +   NH4CL

Sodium hydrogencarbonate is then heated to give sodium carbonate and carbon dioxide.


       2NaHCO3   ==>   Na2CO3   +   CO2   +   H2O

The ammonium chloride is heated with calcium oxide to regenerate the ammonia.

In 1881 Ernest Solvay was the first to successfully use this process. 1872 was the first time that is was used on a large scale.


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