reaction occurs ("slaking of lime"). The temperature can reach up to some . • Heat: Quicklime releases
thermal energy by the formation of the hydrate,
calcium hydroxide, by the following equation: :: (aq) (ΔHr = −63.7kJ/mol of CaO) : As it hydrates, an exothermic reaction results and the solid puffs up. The hydrate can be reconverted to quicklime by removing the water by heating it to redness to reverse the hydration reaction. One litre of water combines with approximately of quicklime to give calcium hydroxide plus 3.54
MJ of energy. This process can be used to provide a convenient portable source of heat, as for on-the-spot food warming in a
self-heating can, cooking, and heating water without open flames. Several companies sell cooking kits using this heating method. • It is a
food additive used as an acidity regulator, a flour treatment agent and a leavener. It has
E number E529. • Light: When quicklime is heated to , it emits an intense glow. This form of illumination is known as a
limelight, and was used broadly in theatrical productions before the invention of electric lighting. • Cement: Calcium oxide is a key ingredient for the process of making
cement. • As a cheap and widely available alkali. • Petroleum industry: Water detection pastes contain a mix of calcium oxide and
phenolphthalein. Should this paste come into contact with water in a fuel storage tank, the CaO reacts with the water to form calcium hydroxide. Calcium hydroxide has a high enough pH to turn the phenolphthalein a vivid purplish-pink color, thus indicating the presence of water. •
Chemical pulping: Calcium oxide is used to make
calcium hydroxide, which is used to regenerate
sodium hydroxide from
sodium carbonate in the chemical recovery at
kraft pulp mills. • Plaster: There is archeological evidence that
Pre-Pottery Neolithic B humans used limestone-based
plaster for flooring and other uses. Such
Lime-ash floor remained in use until the late nineteenth century. • Chemical or power production: Solid sprays or slurries of calcium oxide can be used to remove
sulfur dioxide from exhaust streams in a process called
flue-gas desulfurization. •
Carbon capture and storage: Calcium oxide can be used to capture carbon dioxide from flue gases in a process called
calcium looping. • Mining:
Compressed lime cartridges exploit the exothermic properties of quicklime to break rock. A
shot hole is drilled into the rock in the usual way and a sealed cartridge of quicklime is placed within and
tamped. A quantity of water is then injected into the cartridge and the resulting release of steam, together with the greater volume of the residual hydrated solid, breaks the rock apart. The method does not work if the rock is particularly hard. • Disposal of corpses: Historically, it was mistakenly thought that quicklime was efficacious in accelerating the decomposition of corpses. The application of quicklime can, in fact, promote preservation. Quicklime can aid in eradicating the stench of decomposition, which may have led people to the erroneous conclusion. • It has been determined that the durability of ancient Roman concrete is attributed in part to the use of quicklime as an ingredient. Combined with hot mixing, the quicklime creates macro-sized lime clasts with a characteristically brittle nano-particle architecture. As cracks form in the concrete, they preferentially pass through the structurally weaker lime clasts, fracturing them. When water enters these cracks it creates a calcium-saturated solution which can recrystallize as calcium carbonate, quickly filling the crack. • The thermochemical heat storage mechanism is greatly impacted by the
sintering of CaO and . It demonstrates that the storage materials become less reactive and denser at increasing temperatures. It also pinpoints particular sintering processes and variables influencing the efficiency of these materials in heat storage.
Weapon Quicklime is also thought to have been a component of
Greek fire. Upon contact with water, quicklime would increase its temperature above and ignite the fuel.
David Hume, in his
History of England, recounts that early in the reign of
Henry III, the English Navy destroyed an invading French fleet by blinding the enemy fleet with quicklime. Quicklime may have been used in medieval naval warfare – up to the use of "lime-mortars" to throw it at the enemy ships.
Substitutes Limestone is a substitute for lime in many applications, which include agriculture, fluxing, and sulfur removal. Limestone, which contains less reactive material, is slower to react and may have other disadvantages compared with lime, depending on the application; however, limestone is considerably less expensive than lime. Calcined gypsum is an alternative material in industrial plasters and mortars. Cement, cement kiln dust, fly ash, and lime kiln dust are potential substitutes for some construction uses of lime. Magnesium hydroxide is a substitute for lime in pH control, and magnesium oxide is a substitute for dolomitic lime as a flux in steelmaking. == Safety ==