Calcium hydroxide on a watch glass Calcium hydroxide; Ca(OH)2; Molar mass 74.093??/mol. Also known as Slaked lime, Milk of lime, Calcium II hydroxide, Pickling lime, Hydrated lime, Portlandite, Calcium hydrate, Calcium dihydroxide, cal, E526. It is an??norganic compound and is produced when quick lime or calcium oxide is slaked with water. As E526 it is used in food preparation but it is best known for its use in the building industry to make cement and plaster. Another important use is as a flocculant in sewage and water treatment which calcium hydroxide will remove small particles from. Other uses include raising the pH of water, production of ammonia gas and in paper production.