Calcium hydroxide is a chemical compound with the chemical formula Ca(OH)₂. It is a colorless crystal or white powder, is created when calcium oxide (called lime or quicklime, but unrelated to the citrus fruit (lime)) is slaked with water. A traditional name for calcium hydroxide is slaked lime. It is also called hydrated lime.

If heated, calcium hydroxide decomposes into calcium oxide and water. It is soluble in water and the solution, called lime water, is a medium strong base reacting violently with acids and attacking many metals in presence of water. A suspension of fine calcium hydroxide particles in water is called lime water (or milk of lime), and is widely used in chemical processing.

Calcium hydroxide is mainly used as a form of lime, in water and sewage treatment and improvement of acid soils. Its strong basic properties also give it varied uses, including the tanning of leather.

It is also used as whitewash, mortar, and plaster.

More uses are in:

As a reagent it is used:

• in the tanning industry for neutralization of a superfluous acid;
• in a petroleum-refining industry by manufacture of additives to oils (alkilsalicatic, sulphatic, fenatic);
• in the chemical industry for manufacture of a calcium stearate;
• for neutralization of sour environments, in particular the sewage dumped in reservoirs;
• in the food-processing industry for processing water (by manufacture alcoholic and soft drinks);
• in agro chemistry for processing sour soil;
• for clearing a brine of carbonates of calcium and magnesium by manufacture of salt for food and

pharmacopoeia;

As filler it is used:

• in the petrochemical industry by manufacture solid oil various marks;
• at manufacturing of brakes pads;
• at manufacturing of ebonite;
• for preparation of dry mixes for painting and decorating;
• at manufacturing mixes for protection of agricultural crops from pest (bordeaux a mix);
• at manufacturing a drug "Polikar" for decay fighting (with musty fungus, with rotten stuff) of

vegetables and fruits at their long storage;

An overdose of calcium hydroxide includes many dangerous symptoms, including difficulty breathing, gastrointestinal bleeding, hypotension, and a severe change in blood pH, which is damaging to the internal organs.