108 LIME. 



•whilst the remainder are not bases : that is to say, 

 they seem to have no affinity for acids, and cannot 

 combine with them to form salts. The most import- 

 ant of the earths "which are bases, are called lime, 

 magnesia, and alumine ; the two former are called 

 alkaline earths, to distinguish them from the last, as 

 they possess the property of reddening vegetable 

 colors, though in a far less powerful manner than 

 the alkalies, whilst alumine does not. Silica is not a 

 base. 



226. Lime, in its pure condition, is a highly caustic 

 whitish-gray solid substance, slightly soluble in water, 

 but far less so than the alkalies are. It has a very 

 strong attraction for acids, being even able to decom- 

 pose the salts of the alkalies, in consequence of the 

 superior attraction which it has for the acids contained 

 in them ; and it is for this reason that it is customary 

 to mix quicklime with wood-ash, which contains com- 

 paratively little free potash, as the greater part is 

 combined with carbonic acid (200), when it is desired 

 to make a very strong caustic ley : the quicklime de- 

 composes the carbonate of potash, combines with the 

 carbonic acid, and becomes converted into carbonate 

 of lime ; whilst the potash, being no longer com- 

 bined with an acid, is able to exert its caustic powers. 

 Lime is the oxide of a metal called Calcium (202). 



227. In consequence of its strong affinity for acids, 

 lime never occurs native in a pure and simple state, 

 but always in combination with some acid ; the most 

 common compounds of lime are the carbonate, and 



