Hard water requires more soap and detergent for laundering, cleaning and bathing because suds do not form as well in hard water. The reaction between soap and hard water results in a greasy, curd-like deposit which makes fabrics feel harsh and leaves water spots on dishes and utensils. Mineral scale builds up in hot water appliances and industrial boilers, reducing energy efficiency and shortening appliance and equipment life. Water softeners use cation exchange resin to exchange sodium for calcium and magnesium. As supply water flows through the resin bed, the exchange takes place and the water becomes soft.
Salt is used to manufacture chlorine and caustic soda.
In paper making, caustic soda is used to process wood fibers and chlorine is used to bleach the pulp. Sodium chlorate, also made from salt, is replacing chlorine as the primary chemical for bleaching pulp. Other Industries .