HYDROGEN 



21 



inserting heated elements as we did oxygen, we find that 

 while it is colorless, odorless, and tasteless like oxygen, it 

 has not the power of that element to combine with these 

 other elements or produce combustion. This residual 

 gas which is so lacking in chemical afFmity is an element 

 called nitrogen. Like sulphur, however, its lack of affinity 

 is due rather to lack of the right conditions for combina- 

 tion than to absence of that power. In nature, nitrogen 

 occurs very abundantly in combination with other ele- 

 ments, and some of its compounds form important parts 

 of our body material, notably muscle or flesh. Owing to 

 the weakness of its affinity for most elements its compounds 



are apt to break up readily, and on 

 that account are spoken of as un- 

 stable compounds. Most of our 

 explosives, such as gunpowder and 

 <f ^ nitroglycerine, owe their explosive 



power to the fact that they are 

 unstable compounds of nitrogen. 



j^0.4_^, apparatus for obtaining hydrogen and oxygen with the aid of an electric 

 current. B^ method of collecting the gases. 



Hydrogen. — (See Exs. X. and XI.). If we allow an 

 electric current to pass through water (Fig. 4, A ) which 

 has had a little acid added to it to make it a conductor 



