Calcium hydroxide, traditionally called slaked lime, is an inorganic compound with the chemical formula Ca(OH)2.

It is a colourless crystal or white powder and is obtained when calcium oxide (called lime or quicklime) is mixed, or "slaked" with water.

It has many names including Reef Kalkwasser, hydrated lime, builders lime, slack lime, cal, or pickling lime. It is of low toxicity and finds many applications.

• A flocculant, in water and sewage treatment and improvement of acid soils
• An ingredient in whitewash, mortar, and plaster
• An alkali used as a lye substitute in no-lye hair relaxers
• For reef aquarium hobby for adding bio-available calcium in solution for calcium-using animals such as algae, snails, hard tube worms, and corals (often referred to as Kalkwasser mix), and also to increase the alkalinity of the water

Assay (Ca(OH): >95%
M.F.: Ca(OH)₂
M.W.: 74.09 g/mol
Carbon Dioxide (CO2): <1%
Silica (SiO₂): <1%
Aluminium Oxide (Al₂O₃): <0.20%
Iron Oxide (Fe₂O₃): <0.10%
Sulphur (S): <0.025%
Free Moisture: 0.75%
Arsenic (As): <2.5ppm
Flourine (F): <110ppm
Lead (Pb): <5ppm
Cadmium (Ca): <1ppm
Mercury (Hg): <0.10
Nickel (Ni): <10ppm
Manganese (Mn): <250ppm
Loss on ignistion: 2.8%
BET SSA (m2g): 14-18
Bulk Density: 450-520 kg/m3
Mean Particle Size D50 (um): 7-9

Cas Number: 1305-62-0

Einecs Number: 215-137-3

HS Code / Commodity Code: 2825908590

Hazard Phrases: H315,H318,H335

Prec Phrases: P261,P280,P305+P351+P338