Products
Calcium hydroxide is available in pharmacies and drugstores. It is also called slaked lime or slaked lime.
Structure and properties
Calcium hydroxide (Ca(OH)2, Mr = 74.1 g/mol) exists as a white, fine, and odorless powder that is practically insoluble in water. It is a base with a pKb(1) of 1.37 that reacts with hydrochloric acid, for example:
- Ca(OH)2 (calcium hydroxide) + 2 HCl (hydrochloric acid) CaCl2 (calcium chloride) + 2 H2O (water)
In this process, unlike carbonates, no carbon dioxide is released. Calcium hydroxide can be produced from calcium oxide with water. This reaction is strongly exothermic:
- CaO (calcium oxide) + H2O (water) Ca(OH)2 (calcium hydroxide)
Effects
Calcium hydroxide has basic, corrosive, antiseptic and antifungal properties.
Fields of application
Fields of application include (selection):
- In the food industry as an acidity regulator.
- In dentistry.
- In the quicklime of anesthetic equipment.
- Formerly like magnesium hydroxide for stomach burns and acid regurgitation. In many countries, there are no drugs on the market.
- Used to paint trees against frost and animal frass.
For chemistry experiments in the classroom (detection of carbon dioxide): if carbon dioxide is introduced into an aqueous solution of calcium hydroxide, for example in the form of breathing air, a precipitate of calcium carbonate (lime) is formed:
- Ca(OH)2 (calcium hydroxide) + CO2 (carbon dioxide) CaCO3 (calcium carbonate) + H2O (water)
The formation of calcium carbonate is a consequence of carbonic acid and its dissociation to hydrogen carbonate and carbonate in aqueous solution.
Adverse effects
Calcium hydroxide may cause respiratory irritation and skin irritation and severe eye damage if used improperly. The appropriate precautions in the safety data sheet must be observed (e.g. wearing gloves, safety glasses and protective clothing).
