GALVANIC ELECTRICITY. 



105 



253. DECOMPOSITION OF WATER. If the 



Describe the .. . 



decomposition electrodes are immersed in water, as repre- 



of water. ^^ in the figur ^ the 



water is decomposed, and separated 

 into its elements. Bubbles of hydro- 

 gen collect on the negative electrode, 

 and bubbles of oxygen on the posi- 

 tive, and finally disengage themselves, 

 and rise through the water. 



254. It is to be observed that positive 



Why does hy- . , -1-1 



drogen appear hydrogen is liberated at the negative pole, 



as if the latter had a P ower analogous to 

 that of the magnet for iron, to draw the 

 hydrogen out of the water, in which it exists combined. 

 On the other hand, negative oxygen is liberated at the 

 positive pole, as though the latter had the same attrac- 

 tive power for oxygen. The above figure is given 

 solely for the purpose of illustration. The actual form 

 of apparatus for decomposing water, by the galvanic 

 current, is described in a subsequent paragraph. 



255. THEORY OF THE DECOMPOSITION OF 



Give the theo- . 



ry of the de- WATER. It is a remarkable circumstance, 

 %! sition f in the decomposition just described, that it 

 continues to occur even when the elec- 

 trodes are quite widely separated from each other. Now, 

 a molecule of water is extremely 

 small, and cannot occupy the space 

 between the electrodes, if they are 

 separated to any considerable ex- 

 tent. The space must be occu- 

 pied by many such particles, which, 

 5* 



