10 



'evenly as possible, will usually be sufficient. It is best to allow 

 the heap to stand a few days when it will probably be found that 

 the lumps have crumbled to a fine powder. If a few still remain, 

 they may be either raked out or separated by shoveling over a 

 sand screen. These remaining lumps may be treated with more 

 water or allowed to lie exposed to the weather in the open air 

 until slaked. 



Water-Slaked or Hydrated Lime. — When water is added to 

 caustic or burned lime, intense heat is evolved, due to its chemi- 

 cal union with the calcium oxide, calcium hydrate Ca(0H)2, 

 slaked or hydrated lime resulting. If just sufficient water is added 

 to completely hydrate the lime, a perfectly dry, fine powder will 

 be produced. One hundred pounds of quicklime takes substanti- 

 ally 32 pounds of water, resulting in 132 pounds of dry, slaked 

 lime. This material is an active form of lime not only readily neu- 

 tralizing free soil acids, but also performing all of the other desir- 

 able functions of lime in a most efficient manner. Some of the 

 commercial slaked limes contain an excess of water, i. e., more 

 than enough to combine with the lime. On the other hand, some 

 samples have shown that an insufficient amount of water was 

 used in the slaking process, quicklime still being present in the 

 mixture. 



Air-Slaked Lime. — When caustic lime is exposed to the air it 

 absorbs moisture and carbonic acid slowly, and gradually crumbles 

 to a fine condition. The composition of the material will vary 

 greatly depending upon the length of exposure and other condi- 

 tions. Air-slaked lime is usually classed as a more mild form of 

 lime than either the water-slaked or caustic lime. 



Lime Ashes. — This material is a mixture of ashes from the fuel 

 used in burning lime together with small pieces of lime which 

 fall from the kiln. Lime ashes vary in composition, depending 

 upon the nature of the fuel used in the kiln as well as upon the 

 length of exposure to the weather. All of the lime may be present 

 as carbonate or, if not exposed for too long a time, some of it 

 may be present either as slaked or in caustic form. If a good 

 quality of wood has been used for fuel, there will be some potash 

 and phosphoric acid present, which increases the value for agricul- 

 tural purposes. 



Wood Ashes. — The lime in wood ashes is largely present as 

 carbonate. One hundred pounds of calcium oxide from this 

 source is as valuable as the same amount from fine ground lime- 

 stone, marl or lime ashes. In addition to the lime, wood ashes 

 contain varying quantities of potash in form of carbonate, as 

 well as some phosphoric acid and magnesia, which add to the 

 value of the ashes as a fertilizer. 



