100 CARBONATE OF POTASH. 



study the nature of potassium, sodium, &c., further 

 than to know that they are white silvery-looking 

 metals, which by combining with oxygen form potash 

 and soda. For all practical purposes we may think 

 of potash, soda, and the earths as elementary sub- 

 stances. 



203. Potash has a strong attraction for water ; so 

 that, when dry, pure potash is exposed to the air, it 

 very soon becomes moist, and in a short time has 

 attracted so much water from the air as to appear 

 changed into a liquid. This power of attracting 

 water from the air is common to most of the salts of 

 potash, as well as to many other saline compounds ; 

 it is termed deliquescence, and such salts are said to 

 be deliquescent. Pearlash, if left exposed to the air, 

 rapidly becomes moist, and finally runs into a liquid, 

 which is a very strong solution of that salt in water; 

 pearlash, therefore, must always be kept in a dry 

 place, and in well-closed vessels. 



204. In the same way, we often find that common 

 salt, when kept in a damp place, becomes very moist: 

 this is not occasioned by any attraction which the 

 salt itself has for the moisture in the air, but by 

 certain saline impurities usually contained in the 

 salt, which have this power in a high degree (252). 



205. Chloride of potassium may be formed by 

 heating the metal potassium in chlorine, or by acting 

 upon potash by muriatic acid (190) ; it is not a salt 

 of much interest; it has been occasionally recom- 

 mended as a manure (891). 



