224 Prof. L. Knhlenberg on the 



of the theory of electrolytic dissociation who question whether 

 there is electrolytic dissociation in the case of fused salts, 

 are ready to consider that the fact that the determination 

 of the so-called degree of electrolytic dissociation of pure 

 water by conductivity and electromotive-force measurements 

 leads to approximately the same result, constitutes an argu- 

 ment in favour of the theory in question. 



The theory of electrolytic dissociation and the van't Hoff 

 theory of solutions have done much toward stimulating in- 

 quiry ; but the discovery of many new facts has made them 

 entirely untenable. I do not share the opinion that these 

 hypotheses may be retained in a somewhat modified form. 

 The observed facts that speak against them are by far too 

 numerous ; and furthermore, any theory of solution which 

 holds strictly only for infinitely dilute solutions cannot be 

 expected to maintain itself, for in reality it does not apply at 

 all to any solutions with which we work in practice. 



I have thus briefly rehearsed the reasons why the theories 

 of Arrhenius and van't Hoff are untenable, to me a task far 

 from agreeable, inasmuch as during my student days and for 

 several years afterwards I was quite enthusiastic over these 

 hypotheses, and it was while seeking to establish new ex- 

 perimental facts to further support the theories that contra- 

 dictory phenomena were continually observed. 



I should not like to close these pages without indicating 

 the direction which in my opinion further investigations on 

 solutions must take. All treatises on physics and chemistry 

 seek to draw a sharp distinction between the processes of 

 solution and chemical action ; the former is commonly de- 

 scribed as purely physical in character, the latter as more 

 deep seated and as caused by a specific attraction termed 

 chemical affinity. It is well known that some substances 

 react chemically (using that term in its usual sense) with 

 each other, and again others do not ; and that the rate of 

 interaction and the final condition of equilibrium reached are 

 subject to influences of temperature especially, but also to 

 pressure and concentration. The same may be stated of the 

 process of solution. Some substances dissolve each other, 

 others do not ; and again, the process, like that of chemical 

 action, is subject to influences of temperature, pressure, and 

 concentration. Energy changes, such as thermal changes, 

 electrical changes, expansions and contractions, and evolu- 

 tions of light, are known to accompany the processes of 

 solution as well as those of chemical action. With the ex- 

 ception of the mass, the properties of chemical compounds 

 are never exactly equal to the sum of the properties of the 



