We cannot obtain sodium carbonate directly by treating the (NH₄)₂CO₃ solution with NaCl, sodium chloride. In the Solvay process, carbon dioxide is passed through a concentrated solution of sodium chloride saturated with ammonia, which forms ammonium carbonate followed by ammonium hydrogen carbonate. Ammonium hydrogen carbonate crystals separate and they are heated to form sodium carbonate. NH₃ is recovered from the solution which contains NH₄Cl is heated and treated with Ca(OH)₂. The reaction of (NH₄)₂CO₃ with NaCl gives two products, Na₂CO₃ and NH₄Cl which are both soluble in water which does not shift the equilibrium to the right.

(NH₄)₂CO₃⇌ NH₄Cl + Na₂CO₃