Poly Aluminium Chloride (PAC) is a chemical compound used primarily for water treatment and purification. It is an inorganic polymer coagulant derived from aluminum chloride. PAC is known for its effectiveness in removing suspended solids, organic matter, and colloidal particles from water, making it clearer and safer for various applications such as drinking water treatment, wastewater treatment, and industrial processes. It is available in liquid form and as a solid powder, and its dosage and application depend on specific water quality parameters and treatment objectives.