Calcium Hydroxide (traditionally called Slaked Lime) is an inorganic compound with the chemical formula Ca(OH)2. It is also known as Caustic Lime, Builders’ Lime, Cal and Picking Lime.
CaO + H2O ⟶ Ca(OH)2
Calcium Hydroxide is produced by treating lime with water.
| IUPAC name | Calcium hydroxide |
| Other names | Slaked lime, Milk of lime, Calcium hydroxide, Pickling lime, Hydrated lime, Portlandite, Calcium hydrate, Calcium dihydroxide |
| Chemical formula | Ca(OH)2 |
| Molar mass | 74.093 g/mol |
| Appearance | White powder |
| Odor | Odorless |
| Density | 2.211 g/cm3, solid |
| Melting point | 580°C (1,076°F; 853 K) (loses water, decomposes) |
| Solubility in water |
1.89 g/L (0°C)
1.73 g/L (20°C)
0.66 g/L (100°C)
(retrograde solubility) i.e., unusually decreasing with T |
| Solubility product (Ksp) | 5.02×10−6 |
| Solubility | Soluble in glycerol and acids. Insoluble in ethanol. |
| Acidity (pKa) | 12.63 (first OH−), 11.57 (second OH−) |
| Magnetic susceptibility (χ) | −22.0·10−6 cm3/mol |
| Refractive index (nD) | 1.574 |
| Crystal structure | Hexagonal, hP3 |
| Space group | P3¯m1 No. 164 |
| Lattice constant | a = 0.35853 nm, c = 0.4895 nm |
Unprotected exposure to Ca(OH)2 can cause severe skin irritation, chemical burns, blindness, lung damage or rashes.
Did you know?
Lime is among the oldest and most vital materials used by humans.
Most ancient languages have a word for calcium oxide. In Latin it is calx, from which the name of the element calcium is taken.