Limekilns seem to have come into regular use about the 18th century. The larger stones were used for building but the smaller were burnt to produce lime which was a useful commodity in various ways: it could be spread on the fields, for building purposes or for lime-washing buildings. It was regarded as cleansing and was used not only on farm buildings but often on factories after 1800.
The stone had varying degrees of hardness and therefore took varying times to burn; chalk took about 24 hours and limestone about 60 hours, but the harder stone produced the better product. All kinds of fuel were used in the kilns, wood, coal, turf or other organic products.
The element is a constituent of lime (see calcium oxide calcium oxide, chemical compound, CaO, a colorless, cubic crystalline or white amorphous substance.
), chloride of lime (bleaching powder), mortar mortar, in building, mixture of lime or cement with sand and water, used as a bedding and adhesive between adjacent pieces of stone, brick, or other material in masonry construction.
Lime mortar, a common variety, consists usually of one volume of well-slaked lime to three or four volumes of sand, thoroughly mixed with sufficient water to make a uniform paste easily handled on a trowel.
It is prepared by heating calcium carbonate (e.g., limestone) in a special limekiln to about 500°C to 600°C, decomposing it into the oxide and carbon dioxide.
Calcium oxide is widely used in industry, e.g., in making porcelain and glass; in purifying sugar; in preparing bleaching powder, calcium carbide, and calcium cyanamide; in water softeners; and in mortars and cements.
In agriculture it is used for treating acidic soils (liming).
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