LIMES.
Rich Limes. The common fat or rich are those obtained by calcining pure or very nearly pure carbonate of lime. In slaking they augment to from two to three and a half times that of the original mass. They will not harden under water, or even in damp places excluded from contact with the air. In the air they harden by the gradual formation of carbonate of lime, due to the absorption of car bonic acid gas.
The pastes of fat lime shrink in hardening to such a degree that they cannot -be employed for mortar without a large dose of sand.
Poor Limes. The poor or meagre limes generally contain silica, alumina, magnesia, oxide of iron, sometimes oxide of. man ganese, and in some cases traces of the alkalies, in relative propor tions which vary considerably in different localities. In slaking they proceed sluggiThly, as compared with the rich limes—the action only commences after an interval of from a few minutes to more than an hour after they are wetted; less water is required for the process, and it is attended with less heat and increase of volume than in the case of fat limes.
hydraulic Limes. The hydraulic limes, including the three subdivisions, viz., slightly hydraulic, hydraulic, and eminently hydrau lic, are those containing after calcination sufficient of such foreign constituents as combine chemically with lime and water to confer an appreciable power of setting or hardening under water without the access of air. They slake still slower than the meagre limes, and with but a small augmentation of rarely exceeding 30 per cent of the original bulk.
Lime is shipped either in bulk or in barrels. If in bulk, it is impossible to preserve it for any considerable length of time. A barrel of lime usually weighs about 230 lb. net, and will make about three tenths of a cubic yard of stiff paste. A bushel weighs 75 lb.