Hydrated Lime Powder or Calcium hydroxide is an inorganic compound with the chemical formula Ca(OH)₂. Quick lime is usually a dry powder resulting from the controlled slaking of quicklime with water. The exothermic or released heat of reaction is captured and used to evaporate. It is highly caustic and can burn skin and eyes. It is used in cement and mortar, and it can kill a number of lawn-inhabiting parasites, such as fleas. Farmers often use it on outlying lands to protect animals from parasites that can sicken or kill them. If high concentrations of hydrated lime dust are inhaled, irritation to the respiratory tract will occur.