Calcium hydroxide traditionally called slaked lime, is an inorganic chemical with the chemical formula Ca(OH)2. It is a white powder and is obtained when calcium oxide is mixed with water. When mixed with water, a small proportion of it dissolves, forming a solution known as limewater, the rest remaining as a suspension called milk of lime (see below 'how to make Limewater'). In buon fresco painting limewater is used as the colour solvent to apply on fresh plaster. Limewater is widely used by marine aquarists and is a primary supplement of calcium and alkalinity for reef aquariums. Milk of lime is better known as limewash or whitewash.
Uses for Calcium Hydroxide:
- Used in the manufacture of mortar, render, plaster and whitewash.
- As a flocculant in water and sewage treatment.
- As a chemical alkali
- Lime improves, modifies and stabilises clay soils.
- Lime dries wet soils
- As a disinfectant
- Manufacture of dry mix paints.
How to make limewater
Put 1 tablespoon of calcium hydroxide in a clean glass jar, up to 5 litres in size. (Limewater is a saturated solution, which means there will be some extra chemical that doesn't dissolve. A tablespoon will result in a fully saturated solution whether you use a 5L jar or a smaller one.) Fill the jar with distilled or tap water. Shake the jar vigorously for 1-2 minutes, then let it stand for 24 hours. Being careful not to stir up the sediment, pour the clearer solution off the top of the jar through a clean coffee filter or filter paper. Repeat the filtering step if necessary to obtain a clear limewater solution. Store in a clean jar or bottle.
Properties of calcium hydroxide:
Other names: Slaked lime, Milk of lime, Calcium(II) hydroxide, Calcium dihydroxide, Pickling lime, Building lime, Fat lime, Chemical lime, Finishing lime, Mason’s lime
CAS No: 1305-62-0
EC No: 215-137-3
Appearance: white powder
Molar Mass: 74.09 g/mol
Density: 2.21 g/cm
Melting Point: 580oC
PLEASE NOTE: This product is not for human or animal consumption.