Hydrated Lime, or calcium hydroxide is also recognized among a host of other identifiers including caustic lime, builders’ lime, slack lime, cal, or pickling lime. It is an inorganic compound that is a non-flammable, odorless, colorless white crystal or powder.
Although hydrated lime is relatively insoluble in water, at ambient temperature the inorganic compound dissolves in pure water to produce an alkaline solution with a pH of about 12.4. Aqueous solutions of hydrated lime are called limewater; medium strength bases that react with acids that can attack some metals such as aluminum while protecting other metals from corrosion such as iron and steel by passivation of their surfaces. Hydrated lime adopts a polymeric structure, as do all metal hydroxides. It is produced commercially by treating lime with water.
Besides being a significant flocculant in water and sewage treatment, hydrated lime is also used in the preparation of ammonia gas, and is used in the paper industry where it is part of the causticizing step in the Kraft process for making pulp.
Because of its low toxicity and mildness of its basic properties, slaked lime is widely used in the food industry in everything from clarifying raw juice form sugarcane through carbonatation to pickling cucumbers and other foods.