58 



ELEMENTS OF GENERAL SCIENCE 



FIG. 35. Decomposition 

 of water 



By use of an electric current 

 passed through the water in 

 the tubes the water is de- 

 composed into the hydrogen 

 and oxygen of which it is 

 composed. The upper clear 

 region in the right-hand 

 tube contains hydrogen, and 

 the upper part of the left- 

 hand tube contains oxygen. 

 The volume of hydrogen is 

 twice that of the oxygen 



If we had done so, it would doubtless 

 have been extinguished. Furthermore, 

 if a gas flame is used instead of a candle 

 flame, and every precaution is taken to 

 make sure there is no water vapor either 

 in the gas or in the air, the same result 

 follows. Since this water was produced 

 from substances other than water, it is 

 important for us to know what changes 

 and what substances have produced it. 

 The best way to find what substances 

 compose water is to find what results 

 when water is decomposed. It is not 

 easy to determine what the component 

 parts are, and we shall have to use 

 experiments directly related to that 

 problem. These experiments require 

 the use of an electric current, and in 

 the use of that current many interest- 

 ing problems arise, but we shall give 

 our attention at this time only to those 

 which help us to understand the com- 

 position of water. 



59. The composition of water. When 

 we put the ends of two platinum wires 

 in water and pass a current of elec- 

 tricity through the water between the 

 wires, it is noticed that bubbles of gas 

 arise from both wires. By suitable 

 apparatus it is possible to collect these 

 bubbles until there is enough gas to 

 allow us to examine it (fig. 35). It 

 will be noticed that the volume of gas 

 that may be collected from one wire is 

 about double that collected from the 



