Lime

(lim.) [A. S.] (Chem.) The Oxide of Calcium, which, in the anhydrous state, is known as quick-lime, and is prepared by heating carbonate of lime (limestone or chalk) in kilns, the mineral being mixed with coal. The carbonic acid pa es off at a red heat, and lime is left behind; Form, CaO. Pure lime is a grayish-white porous ma , of sp. gr. 2-3 to 3.0; is infusible at the highest heat of a furnace; has very great affinity for water. When moistened, lime becomes very hot, a great deal of steam is evolved, and the ma soon crumbles to a dry white powder. This is called the slaking of lime. Lime containing many impurities, such as silicates, slakes slowly. The resulting compound known as hydrate of lime, or slaked lime (CaHO), is a soft white powder slightly soluble in water, and crystallizing from its aqueous solution in prisms; the whole of the water is driven n off at a red heat; the solution is alkaline to test-paper. Lime is a powerful base, and saturates acids, forming well-defined salts. Its uses in the arts are very numerous. It is also largely employed in the preparation of mortars and cements. As a manure, it has been for many centuries the chief substance employed for acting chemically upon the constituents of the soil, so as to render them more serviceable to the plant, modifying in a very important manner both the organic and mineral portions of the soil. Its action upon the former consists in promoting its decay, and the conversion of its elements into those forms, viz., carbonic acid, water, ammonia, and nitric acid, in which they maybe of service to the plant. Upon the inorganic constituents of the soil lime acts by a isting the decomposition of minerals, particularly of those which contain alkalies (such as feldspar), and thus converting them into soluble forms. (Bot.) See CITRUS. [s. 545]