AbstractThe paper deals with methods of neutralising acid from waste liquors and rinse water; the precipitation of chromium, copper, iron, etc.; the removal of cyanide in effluents; the construction of effluent treatment tanks of suitable acid-proof materials; the measurement of flow and pH recording apparatus; the removal and scrubbing of nitrous oxide fumes from bright dipping plants, figures for intake air velocity on extractors, and hard rubber as protective lining for tanks and fan casings; study of the recovery of waste pickle liquors from industrial pickling plants; description of plant for the crystallisation of ferrous sulphate.