PAC (Poly aluminium Chloride) referred to as PAC. Usually referred to as Basic or a coagulant such as aluminum chloride, which is between ALCL3 and AL (OH) 3 between a water-soluble inorganic polymers, chemistry the general formula: [Al2(OH)n Cl6-n]m where m on behalf of polymerization degree, n said that the neutral level of PAC products. The color yellow or light yellow, dark brown, dark gray resin-like solid. The product has a strong bridge adsorption performance, during the hydrolysis process, accompanied by cohesion occurs, adsorption and precipitation and other physical chemical processes