114 PHYSICAL SCIENCE 



ions are free from each other, and move in- 

 dependently of each other through the Hquid 

 under an electric force : free from union with 

 each other, let us observe, not necessarily free 

 from combination, chemical or other, with the 

 solvent. As already indicated, the dissociation 

 theory does not depend on any particular view 

 as to the nature of solution in general. 



For aqueous solutions, then, the evidence 

 in favour of the dissociation hypothesis is very 

 strong, and it can safely be used as a working 

 hypothesis to co-ordinate the known phenomena, 

 and to guide future research. For solutions in 

 other solvents, less evidence is yet available ; 

 though for solutions of certain salts in alcohol, 

 the laws of the electrolysis seem to be similar 

 to those of aqueous solutions and to indicate 

 a similar theory. In fused salts, which also 

 conduct electricity and suffer chemical decom- 

 position at the electrodes, the conditions are 

 perhaps different, and we must wait for further 

 light before we can profitably theorise about the 

 nature of the conduction process. 



« 



Besides explaining the electrical and osmotic 

 properties of solutions, the dissociation theory, 

 in the domain of chemistry, has proved one of 

 the most fruitful generalisations that has ever 

 been formulated. Solutions of salts and acids, 

 electrolytes in fact, are the solutions which 

 exhibit chemical activity In the highest degree. 

 In them, the ions alone are concerned in chemical 

 action, and so clearly is this the case, that, as 

 soon as the subject is examined, the ordinary 

 chemical tests for the presence of salts are seen 



