136 METALS AND THEIR COMBINATIONS. 



manufacturing potash is very limited, and is rapidly decreasing, as, 

 fortunately, an almost unlimited supply of soluble potassium salts is 

 furnished by the salt-mines of Stassfurt, Germany, where large quan- 

 tities of potassium chloride (combined or mixed with the chlorides 

 and sulphates of sodium, magnesium, calcium, and other salts) are 

 found, from which the carbonate and other salts are manufactured. 



/ Potassium hydroxide. Potassium hydrate, Potassa, KOH=56 

 (^Caustic potash), may be Attained by the action of the metal on water : 



+ H 2 O = H + KOH. 

 The usilal process for making potassium hydroxide is to boil together 

 a dilute solution of potassium carbonate or bicarbonate and calcium 



hydroxide : 



K 2 CO 3 + Ca(OH) 2 == CaCO 3 -f 2KOH. 



Experiment 16. Add gradually 5 grammes of calcium hydroxide (slaked 

 lime) to a boiling solution of about 5 grammes of potassium carbonate in 50 

 c.c. of water, and continue to boil until the conversion of potassium carbonate 

 into hydroxide is complete. This can be shown by filtering off a few drops of 

 the liquid, and supersaturating with dilute hydrochloric acid, which should not 

 cause effervescence. Set aside to cool, and when all solids have subsided, pour 

 off the clear solution of potassium hydroxide, which may be used for Experi- 

 ment 17. What quantities of K 2 CO 3 and Ca(OH) 2 are required to make one liter 

 of a 5 per cent, solution of potassium hydroxide ? 



Potassium hydroxide is a white, hard, highly deliquescent sub- 

 stance, soluble in 0.5 part of water and 2 parts of alcohol ; it fuses 

 at a low red heat, forming an oily liquid, which may be poured into 

 (suitable moulds to form pencils ; at a strong red heat it is slowly 

 Volatilized without decomposition ; it is strongly alkaline and a 

 powerful base, readily combining with all acids ; itrajjidl^jlsairoys 

 organicjiggiies,, and when taken internally acts as a powerful corrosive, 

 and most likely otherwise as a poison 



Antidotes : dilute acids, vinegar, to form salts ; or fat, oil, or milk, 

 to form soap. 



Liquor potassce is a 5 per cent, solution of potassium hydroxide 

 in water. 



Potassa with lime is a mixture of equal parts of potassium hydroxide 

 and calcium oxide. 



Potassium oxide, K 2 O. This compound can be obtained either 

 by burning potassium in air and subsequent heating of the product 

 to a high temperature, or by fusing together potassium hydroxide 

 and metallic potassium : 



2KOH + 2K = 2K 2 + 2H 



