kalkmilch

Kalkmilch, also known as milk of lime, is an aqueous suspension of calcium hydroxide (Ca(OH)2) in water. It appears milky due to undissolved particles, in contrast to limewater, which is a clearer saturated solution of calcium hydroxide. Kalkmilch is commonly used in traditional whitewashing and as a component in various lime-based applications.

Chemistry and preparation

Calcium hydroxide is produced by slaking quicklime (CaO) with water, releasing heat and giving a suspension of Ca(OH)2 in water. Kalkmilch is typically a moderately concentrated suspension; only a portion of the solid dissolves to form a shallowly saturated solution, while the rest remains as fine suspended particles. The pH of kalkmilch is highly alkaline, reflecting the presence of hydroxide ions.

Applications

One traditional use is limewash in construction, where Kalkmilch is applied to walls to create a breathable white coating that protects and beautifies historic and rural buildings. In laboratory and field contexts, limewater (the clearer Ca(OH)2 solution) is used to detect carbon dioxide, as CO2 causes the suspension to precipitate calcium carbonate and turn cloudy. Kalkmilch can also be used in agricultural practices as a source of calcium for soil liming, helping to raise soil pH in acidic soils, and in some industrial processes that require a caustic, alkaline reagent.

Safety and storage

Calcium hydroxide is caustic and can cause skin and eye irritation. Prolonged exposure should be avoided, and handling should include appropriate protective equipment. Kalkmilch should be stored in a tightly closed container in a cool, dry place, away from acids or moisture that could alter its composition. Regular mixing helps maintain the suspension and prevent settling.