The preparation of the lime is done by first burning and then slaking, or by putting it directly on the land, in an unslaked condition, after its having been burned. Shells are sometimes ground, and used without burning; this is hardly advisable, as they cannot be made so fine as by burning and slaking. As was stated in the first section of this book, lime usually exists in nature, in the form of carbonate of lime, as limestone, chalk, or marble (being lime and carbonic acid combined), and when this is burned, the carbonic acid is thrown off, leaving the lime in a pure or caustic form. This is called burned lime, quick-lime, lime shells, hot lime, etc. If the proper quantity of water be poured on it, it is immediately taken up by the lime, which falls into a dry powder, called slaked lime. If quick-lime were left exposed to the weather, it would absorb moisture from the atmosphere, and become what is termed air slaked.
What is air slaking?
If slaked lime be exposed to the air, what change does it undergo?
What is the object of slaking lime?
How much carbonic acid is contained in a ton of carbonate of lime?
How much lime does a ton of slaked lime contain?
What is the most economical form for transportation?
When slaked lime (consisting of lime and water) is exposed to the atmosphere, it absorbs carbonic acid, and becomes carbonate of lime again; but it is now in the form of a very fine powder, and is much more useful than when in the stone.
If quick-lime is applied directly to the soil, it absorbs first moisture, and then carbonic acid, becoming finally a powdered carbonate of lime.
One ton of carbonate of lime contains 11¼ cwt. of lime; the remainder is carbonic acid. One ton of slaked lime contains about 15 cwt. of lime; the remainder is water.