262 OXIDES. 



other metals, or upon glass, and prevent 

 the experimenter's success. 



Q. Which of the METALS ham the GREATEST 

 affinity to OXYGEN ? 



A. Those called potassium and 

 sodium. 



Potassium and sodium derive their names from 

 potash and soda. Potassa is the oxide of potassium ; 

 and soda is the oxide of sodium. 



Q. How is the affinity of potassium and sodium 

 for oxygen sheum ? 



A. They decompose water the moment 

 they are brought into contact with it. 



Q. What effect has POTASSIUM on WATER ? 



A. It catches fire the moment it is 

 thrown into water, and burns with a 

 vivid flame, which is still further 

 increased by the combustion of hydrogen 

 separated from the water. 



(N. B . Water is composed of oxygen and hydrogen ; 

 and potassium separates the two gases.) 



Q. What effect has SODIUM on WATER ? 



A. It does not take fire as potassium 

 does, but undergoes very rapid oxidation. 



Q. Is the FURR of KETTLES an oxide ? 



A. No; the furr (or deposit of 

 boiling water) is a precipitate of lime 



