Calcium hydroxide
Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula Ca(OH). It is a colorless 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 hydrated lime, caustic lime, builders' lime, slack lime, cal, or pickling lime. Calcium hydroxide is used in many applications, including food preparation, where it has been identified as E number E526. Limewater is the common name for a saturated solution of calcium hydroxide.
Hydroxide
The mineral malachite is a typical example of a basic carbonate. The formula, CuCO(OH) shows that it is halfway between copper carbonate and copper hydroxide. Indeed, in the past the formula was written as CuCO·Cu(OH). The crystal structure is made up of copper, carbonate and hydroxide ions. The mineral atacamite is an example of a basic chloride. It has the formula, CuCl(OH). In this case the composition is nearer to that of the hydroxide than that of the chloride CuCl·3Cu(OH). Copper forms hydroxyphosphate (libethenite), arsenate (olivenite), sulfate (brochantite), and nitrate compounds. White lead is a basic lead carbonate, (PbCO)·Pb(OH), which has been used as a white pigment because of its opaque quality, though its use is now restricted because it can be a source for lead poisoning.