Deutsch: Calciumhydroxid / Español: Hidróxido de Calcio / Português: Hidróxido de Cálcio / Français: Hydroxyde de Calcium / Italiano: Idrossido di Calcio

Calcium hydroxide, known chemically as Ca(OH)₂, is a white powdery substance obtained by mixing calcium oxide (lime) with water, a process known as slaking. In the industrial context, calcium hydroxide plays a versatile role due to its alkaline properties, serving as a key ingredient in many processes and products across various industries.


Calcium hydroxide is characterized by its high solubility in water, which decreases with increasing temperature, and its ability to form suspensions known as lime milk. Its alkaline nature makes it effective for pH control and chemical reactions requiring a basic environment. It is also known for its bactericidal properties.

Application Areas

  • Water Treatment: Used for softening water, neutralizing acidic waste streams, and as a flocculant in sewage treatment.
  • Construction: Integral to making mortars and plasters, providing durability and enhancing workability. Calcium hydroxide reacts with carbon dioxide in the air to form calcium carbonate, a process that improves the strength and stability of the material.
  • Food Industry: Approved as a food additive (E526), calcium hydroxide is used in the processing of drinking water, sugar, and corn, and in the manufacture of pickles and other canned foods to maintain firmness.
  • Agriculture: Used to prepare agricultural lime, which adjusts soil pH levels, improving soil quality and crop yields.
  • Chemical Manufacturing: A component in the production of other chemicals, including calcium hypochlorite, a bleaching agent, and calcium stearate, an additive in plastics.
  • Environmental Applications: Employed in flue gas treatment for the removal of sulfur dioxide from exhaust emissions.

Well-Known Examples

  • In the construction of historical buildings, calcium hydroxide has been used for centuries in mortars and plasters, contributing to their long-term durability.
  • In water treatment facilities, it is used to adjust the pH of water, making it safer for consumption.

Treatment and Risks

Handling calcium hydroxide requires precautions as it can cause skin and respiratory irritation upon contact. In the industrial setting, appropriate safety measures, including the use of personal protective equipment (PPE), are necessary to protect workers. Environmental considerations also guide its use and disposal, particularly in water treatment processes, to prevent harm to aquatic life.

Similar Terms or Synonyms

  • Slaked lime
  • Hydrated lime
  • Lime water (when in solution)
  • Builders' lime


Calcium hydroxide is a highly versatile compound utilized in a wide range of industrial applications, from construction and water treatment to food processing and environmental protection. Its alkaline properties and reactivity make it a valuable resource in numerous chemical and manufacturing processes.


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