POTASH COMPOUNDS. 109 



science. This metal can be kept only in some liquid which 

 contains no oxygen, hence it is immersed for keeping in 

 pure turpentine, or in naphtha, which are compounds of 

 carbon and hydrogen. When exposed to the air it is quick- 

 ly oxidized ; when it is thrown upon water, it floats and ab- 

 sorbs oxygen from this fluid, so rapidly that it takes fire 

 and burns. A curious experiment in this direction may 

 be made by placing a small piece of the metal upon ice, 

 when it at once inflames by combining with the oxygen of 

 the ice. Hydrogen gas is of course liberated in the decom- 

 position of the water. The oxide of potassium thus formed 

 is caustic potash, and weighs one-fifth more than the potas- 

 sium; the increase being due to the oxygen combined. 



CHLORIDE OF POTASSIUM, is very useful as a fertilizer, 

 furnishing to plants not only potash, but chlorine. It ex- 

 ists in sea water along with common salt ; it is found mixed 

 with salt in the salt mines and is extracted in large quan- 

 tities from the salt mines of Germany, from whence it is. 

 brought as "muriate" (chloride) of potash to this country 

 and sold as German potash salts. It consists of potassium 

 combined with chlorine. It can be easily produced by dis- 

 solving pearl ash in hydro-chloric acid, until effervescence 

 ceases and evaporating to dryness. It is extensively used 

 in the manufacture of alum which is a double sulphate of 

 alumina and potash. This salt of potash is found in the 

 ash of nearly all plants, and in large quantities in sea weeds;, 

 salt marsh grasses ; and sedges. 



SULPHATE OF POTASH, consists of potash and sulphuric 

 acid and is a most useful and cheap form from which pot- 

 ash may be furnished to the crops. It may be formed by 

 dissolving the carbonate of potash in sulphuric acid until 

 gas (carbonic acid) is no longer given off, and evaporating 

 the solution. It exists in considerable quantities in wood 

 ashes, and in the ashes of plants; and forms 18 per cent, of 

 the weight of common alum. This salt has been found to 

 act beneficially upon clovers; peas; beans ; cabbages ; tur- 

 nips ; rape and other plants : all of which will be found,, 

 on reference to the preceding tables to contain both potash. 



