CHAPTER IV. 

 Liming the Soil. 



There are two classes of chemical compounds each of which 

 has the power of neutralizing the characteristic properties of the 

 other. 



Lime when applied to the soil has the power as a basic 

 material to neutralize the effects of harmful acids. It is the nat- 

 ural basic material of the soil. 



It is found in abundance and is easily obtained in various 

 forms or compounds, such as limestone, quick lime and water- 

 slaked lime. It is a combination of four substances known as 

 calcium, magnesium, carbon and oxygen. 



Lime is burned from limestone. (Calcium carbonate). 



Quick Lime. 



If we burn 100 pounds of pure dry limestone there are 44 

 pounds of (CO 2 ) carbonic acid gas driven off by heat and there 

 remains 56 pounds of quick lime. 



Water-Slaked Lime. 



If to 56 pounds of quick lime we add 18 pounds of water, the 

 quick lime takes up the water and becomes 74 pounds of water- 

 slaked or hydrated lime (calcium hydrate). 



Air-Slaked Lime. 



Water-slaked lime exposed to the air for several months, 

 absorbs carbonic acid gas, which was driven off by burning the 

 limestone; this continues until it has returned to its original 

 weight of 100 pounds. This is then called air-slaked lime. 



In these different forms of lime such as quicklime, water- 

 slaked lime, and air-slaked lime, there remains the same amount 

 of calcium and magnesium as in the original 100 pounds of lime- 

 stone. 



(48) 



