COMPOUNDS OF SODIUM AND POTASSIUM 171 



factured from this material. Potassium sulphate occurs also 

 in the salt layers, andls~usecl directly as a fertilizer. 



Potassium Carbonate K 2 CO3, Preparation. The water 

 used in scouring wool leaves, when evaporated, the potassium 

 salts of organic acids. When the residue is roasted, potassium 

 carbonate remains. Wood ashes contain considerable amounts 

 of potassium carbonate, and were indeed originally the only 

 source of this compound. The sugar beet takes up exceptional 

 quantities of potassium and, after all the sugar has been removed 

 from the extract, potassium carbonate is obtained by evaporating 

 the liquid and calcining^ the residue. Much of the salt is also 

 manufactured direct from potassium chloride. 



Potassium carbonate is used in making soft soap and difficultly 

 fusible glass (p. 362). 



Potassium Bicarbonate KHCO 3 . When carbon dioxide is 

 led into potassium carbonate solution potassium bicarbonate 

 KHC0 3 is formed: 



C0 2 + H 2 <=> H 2 C0 3 + K 2 C0 3 =* 2KHC0 3 . 



The bicarbonate decomposes easily, especially when warmed, 

 reversing the above action (read the equation backwards). This 

 occurs even in the solution. Hence carbon dioxide can be forced 

 by pressure in large amounts into a warm solution of potassium 

 carbonate, and liberated again by pumping so as to create a 

 vacuum. This plan is used as a means of purifying carbon 

 dioxide (p. 334). The same quantity of potassium carbonate 

 can be used over and over again. 



Potassium Hydroxide KOH. This alkali is made like 

 sodium hydroxide. Either potassium carbonate is treated with 

 slaked lime, or potassium chloride solution is electrolyzed in a 

 Nelson cell (see p. 166). The solution is evaporated, and the 

 substance cast in slender sticks. 



t Co, 



