Ammonium Bisulfite is an inorganic compound that exists as a colourless, pale-yellow solution with a slight sulfur odour. It is formed by the reaction of Ammonia and Sulfurous acid. This seemingly simple compound which is also known as Ammonium Hydrogen Sulfite acts as a powerful oxygen scavenger, a reducing agent and an effective preservative making it a very useful chemical for various applications across a wide range of industries. It is used in water treatment to remove chlorine and other oxidizing agents from water. It helps in neutralising the chlorine ensuring that the water is safe for further industrial use or to be discharged into the environment.