An industrial method of making sodium carbonate from calcium carbonate and sodium chloride. The calcium carbonate is first heated to give calcium oxide and carbon dioxide, which is bubbled into a solution of sodium chloride in ammonia. Sodium hydrogencarbonate is precipitated:H2O+CO2(g)+NaCl(aq)+NH3(aq) → NaHCO3(s)+NH4Cl(aq) The sodium hydrogencarbonate is heated to give sodium carbonate and carbon dioxide. The ammonium chloride is heated with calcium oxide (from the first stage) to regenerate the ammonia. The process was patented in 1861 by the Belgian chemist Ernest Solvay (1838–1922).
H2O+CO2(g)+NaCl(aq)+NH3(aq) → NaHCO3(s)+NH4Cl(aq)