ELECTROLYTIC DISSOCIATION 39 



the heat of neutralization in dilute solutions should be the 

 same for all sorts of strong acids and bases, and should, in 

 fact, equal that produced by the reaction H+OH, a very 

 familiar fact. Mixtures of such salts should not be accom- 

 panied by a heat effect, which explains the phenomenon of 

 thermo-neutrality. But a weak base or a weak acid introduces 

 the positive or negative heat of dissociation pertaining to it; 

 consequently the thermal effect of neutralization must vary 

 from that of H+OH, but this variation must decrease with 

 the increase of temperature. If a stronger and a weaker acid 

 are together mixed with a base, it is only the weaker anion which 

 really unites with the metal to a limited extent, while the 

 stronger anion keeps the relatively greater amount of metal 

 in electrolytic dissociation, their neutralization being charac- 

 terized by the union of their former conjugates H+OH. It is 

 noticeable that electrolytic dissociation is to be sharply 

 separated from the hydrolysis of sugars and of very weak 

 salts like ammonium acetate, in which the reaction belongs 

 rather to the class of non-electrolytes, although electro- 

 lytes are involved. 



A final point with regard to chemical equilibrium is this, 

 that when equilibrium has been reached in a solution con- 

 taining a number of electrolytes, each one of these is in a 

 state of dissociation, which depends upon the equilibrium 

 of osmotic pressure between the non-dissociated molecules 

 and all the free ions of the kinds which compose it. A dis- 

 tribution of metals and acids as it is usually assumed in older 

 views is therefore rendered out of question, because a free 

 ion belongs neither to one compound nor to another, it 

 merely counterbalances that free ion of opposite charge near- 

 est which it happens for the moment to be. 



Having sketched Arrhenius' hypothesis, with some of its 

 logical consequences, the task of judging it must be left to 



