Calcium hydroxide occurs as a white or almost white, crystalline or granular powder

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