Soda liquid waste is produced in Solvay Process. It creates a very big problem for nature. Therefore, the intent of this article is for removal of calcium from soda liquid waste containing calcium chloride. The soda liquid waste was obtained from Mersin Soda Joint Stock Company in Turkey. The soda liquid waste was reacted with chlorine and sulfur dioxide gases. The calcium in waste water was precipitated as gypsum (CaSO4 center dot 2H(2)O). The parameters affected on the precipitation were the chlorine gas feeding rate, the sulfur dioxide gas feeding rate, reaction time, and stirring speed; and then, the best conditions were determined. 2(n) factorial experimental design and ortogonal central composite design methods were used for the optimization of experiments. The effective parameters on the precipitation was observed. The effective parameters were the chlorine gas feeding rate, the sulfur dioxide gas feeding rate, and the reaction time. The optimum conditions were obtained to precipitate maximum calcium. These conditions were: the chlorine gas feeding rate, 1.55 L.min.(-1); the sulfur dioxide gas feeding rate, 1.55 L.min.(-1); the reaction time, 10 min; the stirring speed, 400 rpm; and room temperature, 20 degrees C. Under these optimum conditions, the percentage of precipitating calcium in the form of gypsum was 94.44%.