chemical addition(Chemical reaction in which one or more of the double bonds or triple bonds in an unsaturated compound is converted to a single bond by the addition of other atoms or groups)
softening(Reduction of the hardness of water by removing hardness-forming ions (chiefly calcium and magnesium) by precipitation or ion exchange, or sequestering them as by combining them with substances such as certain phosphates, that form soluble but non-ionized salts)