Calcium hydroxide, also called slaked lime, Ca(OH)2, is obtained by the action of water on calcium oxide. When mixed with water, a small proportion of it dissolves, forming a solution known as limewater, the rest remaining as a suspension called milk of lime. Calcium hydroxide is used as an industrial alkali and as a constituent of mortars, plasters, and cement. It is used in the kraft paper process and as a flocculant in sewage treatment.