One of the main chemicals used in water treatment process are aluminum sulphate used as coagulant thus forming clean water. Aluminum sulfate [Al2(SO4)3] or alum is one of the chemicals that are required both in industry and water treatment companies. This research objective was to study the operating conditions of the process of making solid aluminum sulfate of kaolin and sulfuric acid to see the effect of temperature, time, ratio of sulfuric acid and kaolin, sulfuric acid concentration, the rotation speed of the stirrer and the particle size of solid aluminum sulfate to be generated in order to obtain optimum operating variables process and optimal conversion value. In this research, the process of mixing the sulfuric acid and kaolin, aluminum sulfate paste subsequently extracted with distilled water that has been heated to obtain aluminum sulfate. Fixed variables in this study was the weight and particle size kaolin each 25 grams and 250μm, the condition of the extraction process at a temperature of 100 ° ...