Calcium hydroxide, also known as slaked lime, is an inorganic compound with the chemical formula Ca(OH)2. It is a white powder or colorless crystal formed when calcium oxide (lime or quicklime) is mixed, or slaked, with water. It is relatively inexpensive and is a versatile base used in many applications.
Properties:
- Chemical Formula: Ca(OH)2
- Molar Mass: 74.093 g/mol
- Appearance: White powder or colorless crystals
- Odor: Odorless
- Density: 2.211 g/cm3
- Melting Point: Decomposes at 580 °C (1,076 °F; 853 K)
- Solubility: Slightly soluble in water (the solution is known as limewater), solubility decreases with increasing temperature. Soluble in glycerol and acids. Insoluble in alcohol.
- Basicity: A strong base.
Preparation:
Calcium hydroxide is primarily produced by the hydration of calcium oxide (quicklime) with water:
CaO + H2O → Ca(OH)2
This reaction is exothermic and produces a large amount of heat.
Uses:
- Construction: Used in mortar, plaster, and cement. It improves the workability of mortars and plasters, and contributes to the setting and hardening process.
- Agriculture: Used to treat acidic soils and neutralize acidity. It also provides a source of calcium for plants.
- Wastewater Treatment: Used to neutralize acidic wastewater and precipitate heavy metals.
- Food Industry: Used as a food additive, in the production of pickles, and in the nixtamalization of corn.
- Chemical Industry: Used in the production of other chemicals, such as calcium stearate.
- Dentistry: Used in root canal treatments as an antimicrobial agent.
- Leather Tanning: Used in the liming process to remove hair from hides.
- Paper Manufacturing: Used in the production of paper pulp.
Safety:
Calcium hydroxide is caustic and can cause skin and eye irritation. Inhalation of dust can irritate the respiratory system. Appropriate personal protective equipment, such as gloves, goggles, and a dust mask, should be worn when handling this compound.