LIME. 87 



The rest of the earths are insipid, and are scarce- 

 ly at all soluble in water, and have no action on 



vegetable colours. 



I.IME. 



Lime is one of the most abundant substances in 

 nature. It is the chief constituent in vast moun- 

 tains and rocks, and is very generally distributed, 

 mixed with other earths. Chalk, marble, calcare- 

 ous spar, and all those rocks called lim.e-stones, con- 

 sist of it. 



In these substances, however, the lime is not 

 pure or uncombined. It exists in them united to 

 carbonic acid, constituting carbonate of lime. 



To obtain pure lime, these stones are exposed 

 to a white heat, by which the carbonic acid is 

 driven off in the gaseous state. This is called the 

 huriiing of lime. The stone so treated is then 

 called quicIiHme; or, in chemical language, properly 

 lime. 



Quicklime, or pure lime, is white ; has a hot 

 acrid taste, and is caustic, or corrodes the skin. It 

 changes vegetable blues to green. 



Until the discovery of the bases of the alkalies by 

 Sir Humphry Davy, lime, as well as all the other 

 earths, was considered as an elementary substance ; 

 but it has been ascertained to be the oxide of a 

 metal to which the name of calcium has been given. 

 From the extreme difficulty, however, in reducing 

 lime to this state, the properties of calcium are but 

 little known. It is white and solid, resembling 

 silver, and soon returns to the state of oxide or 

 lime by attracting oxygen from the air. 



When water is thrown on quicklime just burnt, 

 it swells, bursts, and falls to powder; giving out, at 



G 4 



