SALTS OF POTASH. »» 



is left, which is the carbonate of potash separated 

 from most of the other matters which were contained 

 in the ashes, and when thus purified it is called pearl- 

 ash. 



201. Pure potash is readily obtained from its car- 

 bonate, by means of quicklime ; that substance has a 

 stronger affinity for carbonic acid than potash has, 

 and accordingly it decomposes the alkaline carbonate 

 and leaves the alkali in its pure state: when free 

 from any acid, it is found to be a very caustic solid 

 substance, which has a strong affinity for acids, and 

 is difficult to keep perfectly pure, as when exposed 

 to the air it rapidly acquires carbonic acid from it, 

 and becomes converted into the carbonate. 



202. Potash is not a simple substance ; like soda, 

 it is a compound of a metal and oxygen (190). By 

 the action of charcoal at a very high temperature it 

 may be decomposed, for at a white heat the affinity 

 of charcoal for oxygen is so great that it is even able 

 to take it from potassium, as the metal of potash is 

 termed. Potassium is of course never found in a 

 native state, for its affinity for oxygen is so great 

 that when exposed to the air it instantly absorbs a 

 quantity of that gas, and is soon converted into 

 potash. It may readily be proved that potash, soda, 

 and the earths are all compound bodies, and that they 

 consist of peculiar metals combined with oxygen ; but 

 as the affinity which they have for that element is 

 very great, and as they are never decomposed' under 

 ordinary circumstances, it is quite unnecessary to 



