22 



CHEMICAL COMPOSITION OF LIVING MATTER 



of the current, we find that the current has the power to 

 separate the water into two gases. One of the gases is 

 twice as great in volume as the other and shows very 

 different properties. If we collect these gases (Fig. 4, B) 

 and examine them we find that oxygen is the smaller vol- 

 ume. The other gas is colorless, odorless, and tasteless, 

 hke the first, but when we introduce a lighted splinter into 

 it, it takes fire with an explosion and burns with a very 

 hot colorless flame. If, instead of using water and the 

 electric current, we pour sulphui-ic acid upon zinc (Fig. 5) 



the zinc will cause the acid 

 to split and set free large 

 quantities of this same 

 substance which we may 

 collect and examine more 

 carefully.. Such an exami- 

 nation ■will show that not 

 only does this substance 

 burn, but that when it 

 does burn it forms water. 

 This peculiar gas is a chem- 

 ical element called hydro- 

 gen and since burning is 

 simply the result of the combining of an element with 

 oxygen, we must conclude that water is not an element 

 but a compound of hydrogen and oxygen. The explosive 

 force with which this combination takes place shows that 

 the affinity of hydrogen for oxygen is very strong. Hydro- 

 gen has a strong affiijity for many other elements beside 

 oxygen, especially for the element carbon; and its com- 

 pounds with this element form a very large part of living 

 matter. Aside from being one of the most active of 



Fig, 5 — Apparatus arranged for obtain- 

 ing hydrogen from zinc and sulphuric 

 acid. 



