These Campden Tablets are made from compressed Sodium Metabisulphite. Commonly used for treatment of wild yeast on fruit in winemaking. Also used for water treatment to help eliminate Chlorine and Chloramine from town water supplies.
The amount required for water treatment will vary depending on the amount of Chlorine or Chloramine in the water. Generally very small quantities are needed. Typically 1 Tablet per 100 litres of water to be treated.