THE ELEMENTS OF PLANT FOOD 



the crayon, so that the crayon may be lowered into a 

 jar. Place a piece of sulphur the size of a pea in the 

 cup, touch it with a piece of hot iron so that it begins 

 to burn in the air. Lower it into n 



a jar of oxygen and note the beau- 

 tiful blue flame. 



Reaction : S + O 2 = SO2 



Fray out the end of a picture 

 cord wire, heat the frayed end to 

 redness, dip it quickly into flour 

 of sulphur, and then into a jar of 

 O. The sulphur sticking to the 

 cord starts the combustion of the 



FIG. 2, Sulphur burning 

 in Oxygen. 



iron and the oxygen continues it so that the entire cord 

 may be burned, producing very brilliant scintillations. 



A little water should be in the 

 jar to prevent the burning glob- 

 ules of iron from melting or 

 cracking the glass jar. 



Reaction : 3 Fe + 2 O 2 = Fe 3 O 4 



The experiments just de- 

 scribed illustrate the effects of 

 oxygen when unmixed with ni- 

 trogen, but oxygen is also a con- 

 stantly active agent in all the 

 processes of life and decay when found diluted with N 

 in air. 



Since the action is on vegetable or animal matter 

 composed principally of carbon and hydrogen, the prod- 

 ucts of the oxidation are largely carbon dioxide (CO 2 ) 

 and water (H 2 0). 



M. & H. AG. 2 



FIG. 3. 



Wire burning in 

 Oxygen. 



