Molecular formula Al2Cl(OH)5 CAS No.: 1327-41-9 Polyaluminium chlorides are synthetic polymers dissolved in water. They react to form insoluble aluminium poly-hydroxides which precipitate in big volumetric flocs.The flocs absorb suspended pollutants in the water which are precipitated with the PAC and can together be easily removed. Polyaluminium chloride (PAC) is increasingly used for water treatment. Against the conventional use of aluminium sulphate (alum) it is showing distinct advantages.PAC can be used as a flocculant for all types of water treatment treatment, drinking water, industrial waste water, urban waste water and in the paper industry.