248 



LIME 



calcium oxide content only which is of value in neutralizing 

 acids. One hundred pounds of calcium carbonate contain 

 fifty-six pounds of calcium oxide, or to be more in accord 

 with the naturally occurring limestones, one hundred pounds 

 of 95 per cent, limestone contain fifty-three pounds of 

 calcium oxide. 



Fig. 61. — Lime kilns. Department of Experimental Agricultural Chem- 

 istry, Pennsylvania Station. 



(b) Calcium Oxide, called also Burnt Lime, Stone Lime, 

 Lump Lime, Rock Lime, Caustic Lime, and Quicklime, 

 CaO. — This is prepared from any of the forms of calcium 

 carbonate, although usually from limestone, by "burning," 

 either in specially built kilns (Fig. 61) or in piles in the field. 

 In either case the limestone is alternated with wood or coal 

 and the latter by burning produces sufficient heat to drive 

 off carbon dioxide from the limestone and leave calcium 

 oxide, thus : 



CaCOs + heat = CaO + C0 2 . 



If pure this form of lime is all valuable in neutralizing acids 

 and is the most concentrated form that can be obtained. 



