C02b 1/20 US. Cl. 210--58 15 Claims ABSTRACT OF THE DISCLOSURE Formation of hard adherent scale deposits of insoluble salts particularly carbonates and sulfates of metals such as calcium or other alkaline earth metals, and/or iron which may include particles of silt or silica, are inhibited, controlled or prevented on, or removed from (a) the walls of evaporators, cooling towers, heat exchangers,