^64 



life, when in this highly caustic state, is at the same 

 time extremely useful to the agriculturist, in assisting to 

 destroy not only noxious weeds, but in ridding the soil 

 of the larvse and eggs of various destructive insects, which 

 would otherwise prey upon the crop. 



But perhaps its most important office, as Quick Lime, 

 is to release the potash, locked up, as it were, in the soil, 

 by rendering it soluble, and indirectly acting upon the 

 silica, so necessary for the healthy and luxuriant growth 

 of the cereal plants, Liebig, in treating upon this subject, 

 says — " In order to form a proper conception of the action 

 of Lime on soils, we must remember the processes employed 

 by chemists to effect the speedy decomposition of a mineral, 

 and to render soluble its ingredients. In order to dissolve 

 finely pulverised felspar in an acid, it would be necessary 

 to expose it to continued digestion for weeks, or even months. 

 But when the felspar is mixed with Lime, and is exposed 

 to a moderately strong heat, the Lime enters into chemical 

 combination with the constituents of the felspar. A part 

 of the alkali (potash) imprisoned in the felspar is now set 

 at liberty, and its simple treatment with acid, in the cold, 

 now suffices to dissolve the Lime, and other constituents 

 of the mineral. The silica is dissolved by the acid to such 

 an extent, that the whole assumes the consistence of a 

 transparent jelly. Most of the silicates of alumina, when 

 mixed with Slaked Lime, and kept in continued contact 

 in a moist state, behave in a similar manner to felspar 

 when heated with Lime. When a mixture of common 

 clay and water is added to the milk of Lime, and they are 

 left in contact for several months, it is found that the 

 mixture gelatinizes on the addition of an acid. The clay 

 is broken up by the union of certain of its constituents 

 with Lime, and most of the alkalis contained in it are 

 set at liberty. These experiments have explained the action 



