74 CHEMISTRY, GEOLOGY 



lime, and is no longer caustic, or hot. The 

 heat produced in the process of slaking is some- 

 times so great as to set fire to gunpowder placed 

 upon a dry portion of the mass, and a cold 

 baked pie, may be thoroughly heated by being 

 placed upon the slaking lime. Occasionally the 

 heat given off sets fire to the sod with which 

 heaps of lime are sometimes covered in the field. 



One ton of pure quick-lime, after slaking, 

 weighs twenty-five hundred pounds, the ton of 

 lime having absorbed and retained five hundred 

 weight of water. 



Quick-lime falls to powder gradually if ex- 

 posed to the atmosphere, because it absorbs the 

 water contained in the air. 



In addition to the water from the atmosphere, 

 quick-lime absorbs a portion of its carbonic acid, 

 and is again changed to the state of mild carbon- 

 ate. You may see this change effected, by pour- 

 ing a little clear lime-water into a tumbler-glass, 

 which will, in a short time, be covered with a 

 thin film of the carbonate of lime. 



Questions. What change has the quick-lime undergone .' 

 How much weight does a ton of lime gain in slaking ? Does 

 lime become slaked in any other mode ? Does the air effect 

 any other change in quick-lime ? 



