MANCKES. 145 



Aate 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 burn- 

 ed 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-lhne were 

 left exposed to the weather it would absorb moisture 

 from the atmosphere, and become what is termed 

 air-slaked. 



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, or even when finely 

 ground. 



If quick-lime is applied directlj- to the soil, it 

 absorbs first moisture, and then carbonic acid, becom- 

 ing finally a powdered carbonate of lime. 



One ton of carhonate of lime contains 11^ cwt. 

 of lime ; the remainder is carbonic acid. One ton 

 of slaked lime contains about 15 cwt. of lime ; the 

 remainder is water. 



Hence we see that lime should be bm-ned, and not 

 slaked, before being transported, as it would be un- 

 profitable to transport the large quantity of carbonic 

 acid and water contained in carbonate of lime and 

 slaked lime. The quick-lime may be slaked and 

 carbonated after reaching its destination, either be- 

 fore or after being applied to the land. 



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