Calcium hydroxide

Chemical compound

Calcium hydroxide, traditionally called slaked lime, is an inorganic compound with the chemical 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. It has many names including hydrated lime, caustic lime, builders' lime, slack lime, cal, or pickling lime. Calcium hydroxide is used in many applications, including food preparation, construction, and chemical processes.

Properties

Calcium hydroxide is a soft, white, powdery solid with a slightly bitter taste. It is sparingly soluble in water, with a solubility of about 1.5 g/L at 25 °C. The solution is called lime water, and it is a medium strength base that reacts with acids to form salts. The solubility decreases with increasing temperature, which is unusual for most salts.

Calcium hydroxide

Production

Calcium hydroxide is produced by mixing calcium oxide (CaO) with water in a process called slaking:

CaO + H₂O → Ca(OH)₂

This reaction is exothermic and releases heat. The resulting product is a fine white powder that is used in various applications.

Applications

Construction

In the construction industry, calcium hydroxide is used as a key ingredient in mortar and plaster. It is also used in the production of concrete and as a pH modifier in soil stabilization.

Food Industry

Calcium hydroxide is used in the food industry for processing corn into nixtamal, which is used to make tortillas and tamales. This process, known as nixtamalization, improves the nutritional value of the corn and enhances its flavor.

Nixtamalized corn, a process involving calcium hydroxide

Chemical Industry

In the chemical industry, calcium hydroxide is used as a pH regulator and as a source of calcium ions. It is also used in the production of calcium salts and as a flocculant in water and sewage treatment.

Other Uses

Calcium hydroxide is used in the leather industry for dehairing hides and in the paper industry for pulp production. It is also used in the sugar industry to purify raw sugar.

Safety

Calcium hydroxide is considered to be a low hazard material, but it can cause skin irritation and eye damage upon contact. It is important to handle it with care and use appropriate protective equipment.

Related pages

• Calcium oxide
• Lime (material)
• Nixtamalization
• Mortar (masonry)