One of the by-products formed during the recovery of NH3 from Solvay process is :

The Solvay process is an industrial process used to produce sodium carbonate, also known as soda ash. The process converts ammonia and carbon dioxide into concentrated salt brine, which is then treated with calcium hydroxide to form a precipitate of calcium carbonate and ammonium chloride (NH4Cl). The calcium carbonate is filtered out, leaving behind the ammonium chloride. The result of this process is primarily sodium carbonate along with calcium hydroxide (Ca(OH)2), sodium hydrogen carbonate (NaHCO3) and ammonium chloride (NH4Cl).