A hot caustic substance, employed in the composition of mortar for buildings; by farmers, as a manure; by bleachers, tanners, sugar-bakers, soap-boilers, and iron-masters, in the preparation of various manufactures; and also in medicine. Quicklime is obtained from chalk, marble, limestone, oyster-shells, etc. by expelling from them, by means of heat, the carbonic acid and water with which they are combined. The quantity of quicklime obtained from a ton of limestone, if weighed when hot from the kiln, is on an average, according to the experiments of Bishop Watson, 11 cwt. 1 qr. 4 lb. By exposure to the air also, a ton of quicklime acquires daily the additional weight of about one twentieth part of itself, for the first five or six days after it is drawn; and therefore, the earlier it is used the better. Quicklime, to be reserved for chemical or medicinal uses, should be kept in bottles well stopped.