In this process, finely divided gypsum is added to a solution of ammonium carbonate causing calcium carbonate precipitates as a solid, leaving ammonium sulfate in the solution: N H 4 2 C O 3 + CaSO 4 → N H 4 2 SO 4 + CaCO 3. After formation of the ammonium sulfate solution, manufacturing operations of each process are similar.