lime(redirected from air-slaked lime)
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lime, in botany
lime, in botany, small shrublike tree (Citrus aurantifolia) of the family Rutaceae (rue family), one of the citrus fruit trees, similar to the lemon but more spreading and irregular in growth. The true lime, a natural hybrid of the citron and papeda, is native to SE Asia and has been introduced into S Europe, the West Indies, Mexico, Florida, and California. Chief production is in tropical regions of the Old and New World; most true limes in American commerce, often known as Key or Mexican limes, come from Mexico or the West Indies. The lime is the most susceptible to frost injury of all citrus fruits, but some varieties do well in sandy or rocky soils usually unfavorable to citrus.
The bright green fruit is smaller than the lemon, more globular, more acid, and with a thinner rind. It has the vitamin value and other properties of the citrus fruits. The juice has long been known as a preventive against scurvy and is one of the main sources of citric acid.
The predominant lime in American cuisine is a larger, more mildly flavored, typically seedless cross, C. latifolia, between the true lime and citron, known as a Persian, Tahitian, or Bearss lime, and there are a number of other citrus fruits called limes. The name lime is also applied to the unrelated linden and sometimes to a species of tupelo, or sour gum, known also as the Ogeechee lime.
Limes are classified in the division Magnoliophyta, class Magnoliopsida, order Sapindales, family Rutaceae.
an arbitrary general term for the products of calcination and subsequent processing of limestone, chalk, and other carbonaceous rocks. The term is usually used for both unslaked lime, CaO, and the product of its reaction with water, slaked lime, Ca(OH)2. Lime is used extensively in construction, metallurgy, and the chemical industry; in the production of sugar, paper, and glass; in agriculture; and for water purification. Other forms of lime are soda lime and bleaching powder.
Building lime is a binder. It contains up to 95 percent CaO. It is produced by calcination of natural calcium and magnesium carbonates at 1100°-1300°C in shaft and rotary furnaces. Lime is one of the oldest binders. It was used in a mixture with sand and water as early as 3000–2500 B.C. to bind stones and bricks in various buildings, as well as for making plaster mortars and colored compounds. Under the action of carbon dioxide in the air, such a mixture gradually hardens through the formation of crystalline calcium carbonate and evaporation of water:
Ca(OH)2 + CO2 = CaCO3 + H2O
In modern construction, lime is used to make mortars and concretes, silica brick and artificial building stone, and blocks. Depending on its chemical composition, a distinction is made between air-hardening lime, which consists primarily of calcium and magnesium oxides, and hydraulic lime, which in addition contains a considerable quantity of silicon, aluminum, and iron oxides. Air-hardening lime makes possible the hardening of mortars and concretes and the retention of strength under air-dry conditions; hydraulic lime provides these properties in both air and water. In construction, a distinction is made between ball and powdered lime; the latter is divided into unslaked ground lime and hydrated lime (calcium hydroxide), which is produced by slaking (hydration) of calcium, magnesian, and dolomitic lime with a small amount of water. Treatment of unslaked lime with excess water gives lime paste. The most promising uses of lime are in the production of silica brick, autoclave silicate-concrete articles and structural members, and mixed lime-slag and lime-pozzolanic binders.