Slaked lime

Slaked Lime

Slaked lime, also known as calcium hydroxide, is a chemical compound with the formula Ca(OH)₂. It is a colorless crystal or white powder and is obtained when calcium oxide (quicklime) is mixed, or "slaked" with water. Slaked lime is an important industrial chemical and is used in a variety of applications, including construction, water treatment, and food preparation.

Properties

Slaked lime is a soft, white, crystalline powder. It is slightly soluble in water, forming a solution known as lime water. The solubility of calcium hydroxide decreases with increasing temperature. It is a strong base and reacts with acids to form calcium salts. The chemical reaction for the formation of slaked lime is:

\[ \text{CaO} + \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 \]

Production

Slaked lime is produced by adding water to quicklime (calcium oxide). The process is exothermic and releases a significant amount of heat. The reaction is carefully controlled to ensure that the correct amount of water is added to produce the desired form of calcium hydroxide.

Uses

Construction

In construction, slaked lime is used to make lime mortar and lime plaster. It is valued for its ability to set and harden under water, making it ideal for use in damp environments. Lime mortar is used in the restoration of historic buildings because it is more flexible and breathable than modern cement-based mortars.

Water Treatment

Slaked lime is used in water treatment to adjust pH levels and to remove impurities. It is effective in softening water by removing carbonate hardness. It also helps in the removal of heavy metals and other contaminants.

Food Preparation

In food preparation, slaked lime is used in the process of nixtamalization, where it is used to treat corn. This process improves the nutritional value of corn and enhances its flavor. It is also used in the preparation of pickles and other preserved foods.

Safety

Calcium hydroxide is a strong base and can cause skin irritation and chemical burns. It should be handled with care, using appropriate personal protective equipment such as gloves and goggles. Inhalation of dust can cause respiratory irritation.

Also see

• Calcium oxide
• Lime mortar
• Water treatment
• Nixtamalization