Calcium Hydroxide

Calcium Hydroxide

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Calcium Hydroxide

Calcium hydroxide occurs as a white or almost white, crystalline or granular powder. It has a bitter, alkaline taste. Calcium hydroxide readily absorbs carbon dioxide to form calcium carbonate.

Nonproprietary Names

  • BP: Calcium Hydroxide
  • JP: Calcium Hydroxide
  • PhEur: Calcium Hydroxide
  • USP: Calcium Hydroxide


Calcium hydrate; calcii hydroxidum; E526; hydrated lime; slaked lime.

Chemical Name and CAS Registry Number: Calcium hydroxide [1305-62-0]

Empirical Formula and Molecular Weight: Ca(OH)2 74.1

Functional Category: Alkalizing agent; astringent; therapeutic agent.

Applications in Pharmaceutical Formulation or Technology

Calcium hydroxide is a strong alkali and is used as a pharmaceutical pH adjuster/buffer and antacid in topical medicinal ointments, creams, lotions, and suspensions, often as an aqueous solution (lime water). It forms calcium soaps of fatty acids, which produce water-in-oil emulsions (calamine liniment), and it is also used as a topical astringent.


Calcium hydroxide is a common cosmetic ingredient in hairstraightening and hair-removal products, and in shaving preparations. In dentistry, it is used as a filling agent and in dental pastes to encourage deposition of secondary dentine. Calcium hydroxide was traditionally used as an escharotic in Vienna Paste.

Method of Manufacture
: Calcium hydroxide is manufactured by adding water to calcium oxide, a process called slaking.

Related Substances: Potassium hydroxide; sodium hydroxide

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