A process is provided for recovering sodium bicarbonate and ammonium sulfate from a solution containing sodium sulfate derived from a process for removing sulfur contaminants out of a gas with sodium bicarbonate reagent. Sodium bicarbonate is precipitated and removed from the solution. Sodium sulfate or ammonium bicarbonate is added to the solution to form a second precipitate of sodium bicarbonate, which is removed from the solution. The solution is conditioned by either heating the solution to 95.degree. C. to liberate ammonia and carbon dioxide or by adding sulfuric acid to the solution to decompose any carbonates. The solution is cooled to a temperature between -2 to 2.degree. C. to form a third precipitate of sodium bicarbonate. Sulfuric acid is added to the solution to decompose any carbonate minerals, and purified ammonium sulfate solution is recovered.