Whiting is a fine carbonate of lime, made in some places by grinding soft chalk in a mill, separating the finer particles by washing them over in water, letting the water settle, and making up the sediment into loaves, which are exposed to the air to dry. There are numerous manufactories beside the river Thames, where whiting is thus prepared, the loaves being exposed on shelves in lofty sheds, which form, as it were, the vertical external walls of the buildings. In some places whiting is made from lime by slaking it with a little water, then grinding it in a mill with water, exposing the lime water to the air for some time to absorb the carbonic acid from the atmosphere, washing over the sediment, making it into loaves, and drying them. When made into small loaves it is called Spanish white; and if in small drops, prepared chalk ; the creta preparata of the apothecaries. It is principally used as a white paint, either alone, or mixed with white lead ; the inferior priced white lead has a large proportion of whiting mixed with it. Spanish white and prepared chalk are likewise exten sively used to saturate acids in liquids in various chemical and manufacturing operations.
Lime with water form a paste of but little cohesion; for common mortar is mixed with rough sand to give it firmness; but the mortar for the outermost covering of in4om work, is mixed with hair to give it cohesion without lessen ing its capability of receiving a smooth surface. As lime absorbs carbonic acid gas as well as water from -the atmosphere, it should be made into mortar before it has imbibed any, considerable portion of it, otherwise it will be of little value. It is by the absorption of carbonic acid that mortar acquires hardness, its lime being slowly converted again into the state of limestone; but the hardness will not be perfect unless undisturbed from its commencement; when this cir cumstance is observed it soon acquires a Moderate degree of hardness, but ages are probably required for it to attain its maximum. The silex or sand mixed with lime operates by hastening its crystallization. Lime, though infuaible alone, promotes the fusion of all the other earths, and is extensively used in smelting iron ores ; it serves as a flux to the alumine and silex which the ores of that metal contain.
Marl, which is of so much value in agriculture, consists of a mixture of lime and clay, and it is the calcareous part of its composition to which its value is owing; if the quantity of lime in it do not exceed 30 per cent. it is worth
less. Every good awl contains a portion of carbonate of lime, which mate rially!useists m retaining the moisture necessary to active vegetation. Limestone contenting mush magnesia is unfit to afford lime for the farmer's use ; it may be known from good limestone by its being much longer in dissolving in acids. Lime is used by the soap manufacturer to render his soda caustic: it enters into the composition of glass, which it renders less liable to attract moisture, and less brittle than it would otherwise be. It is employed in the manufacture of glue to prevent its becoming flexible by the ready absorption of moisture. It is used by the tanner to facilitate the removal of the ban from skins. It is used by the sugar refiner to absorb the acid, which would prevent the sugar from crystallizing. A solution of lime is employed to cleanse feathers from their mime] oil, and render them sweet and fit for use. Acids dissolve pure lime with effervescence, but heat is evolved during the solution. Water impregnated with carbonic add will dissolve a much larger quantity of it than before ; and when deprived of this acid by exposure to the air, the lime it held in solution is precipitated ; hence the formation of stalactites and incrustations found in caverns. The crystals of the solutions of lime in acids form what are called spars. The beautiful spar called fluor spar, or Derbyshire spar, is a fluate of hire, that is, a combination of lime and tbe fluonc acid. Combined with muriatic acid, large quantities of lime are held in solution by the waters of the ocean. Combined with sulphuric acid lime forms • gypsum, when cal cined by a moderate heat, is called plaster of Paris. Combined with the oxymunatic acid, or chlorine, it forms chloride of lime, the famous salt used in BLEACHING, (which see.) Combined with phosphoric acid, lime forms the solid parts of the bones of all animals. The shells of testaceous animals consist chiefly of carbonate of lime cemented by a small portion of animal glue; while those of crustaceous animals always contain more or less of phosphate of lime, which approximates them to the nature of bone.