Life and Chemistry 183 



the chlorine one way and the sodium the 

 other way, so that they can be removed at 

 an electrode and their place supplied by 

 freshly dissociated molecules of salt, thus 

 bringing about its permanent electro- 

 chemical decomposition, and enabling the 

 water to behave as an electrolytic conductor 

 directly a little salt or acid is dissolved 

 in it. 



The power of the water molecule to 

 associate itself with molecules of other 

 substances is illustrated by the well-known 

 fact that water is an almost universal solvent. 

 It is its residual affinity which enables it to 

 enter into weak chemical combination with 

 a large number of other substances, and thus 

 to dissolve those substances. The dissolving 

 power usually increases when the tempera- 

 ture is raised, possibly because the self- 

 contained or self-sufficient groupings of the 

 water molecules are then to some extent 

 broken up and the fragments enabled to 

 cling on to the foreign or introduced matter 

 instead of only to each other. The foreign 



