THE ELEMENTS OF PLANT FOOD 51 



Potassium Sulphate (K 2 SO 4 ). - - This is prepared 

 from some of the Stassfurt salts and furnishes a large 

 percentage of potassium in the compound. It is 

 especially valuable as a fertilizer because it can be 

 applied in places where potassium chloride (KC1) 

 cannot, the latter being destructive of vegetable life if 

 applied directly to the planto. 



Note. Vast amounts of potassium salts have been mined in the 

 Stassfurt salt mines in Germany. Many thousand tons of these salts 

 are shipped annually to all parts of the world. The Stassfurt mines 

 were first mined for rock salt and the potassium salts were regarded as 

 troublesome impurities. The great value of these salts was soon found 

 out, and supplying them to the world has become one of the greatest 

 industries of Germany. 



Potassium hydroxide (KOH), caustic potash, is a 

 white solid usually sold in the form of sticks about 

 the size of a lead pencil. The sticks are kept in closed 

 bottles, as the hydroxide attracts the moisture in the 

 air and CO 2 slowly changes it to K 2 COs (potassium 

 carbonate). Potassium hydroxide is one of the 

 strongest alkalies known. It quickly destroys both 

 animal and vegetable substances, and hence should 

 not be touched with bare hands. It unites with grease 

 to form soft soap. 



Kainit. Kainit is a low grade of potassium salt 

 mined in Germany. It is used as a fertilizer very 

 extensively. Although it contains but a small amount 

 of potash compared with other potassium fertilizers, it 

 is considered valuable because of its action in ren- 

 dering available nitrogen compounds in the soil. It 

 consists of potassium sulphate and magnesium chlo- 

 ride. 



