﻿20 Molecular Constitution of Aqueous Solutions. 



in acids and o£ the OH ion in alkalies, it is shown that the 

 large exceptional ionic velocities assigned to these ions are 

 not their true velocities. Both of these ions cause H 2 to 

 dissociate into H and OH. At ordinary temperature each H 

 dissociates 192 H 2 0, and each OH 0'86 H 2 0. The ionic 

 velocity hitherto assigned to H is the sum of 2'92 times the 

 true velocity of H and 1*92 times that of OH. Similarly 

 the velocity hitherto assigned to OH is 1*86 times the true 

 velocity of OH and 0*86 times that of H. The true velocities 

 of H and OH conform to the law \B3K/i/= constant (where v 

 is valency), to which their hitherto accepted velocities make 

 them decided exceptions, and thus they confirm it. 



The departure of the specific heats of solutions from the 

 simple law of mixtures is traced to the change of (H 2 0) 3 into 

 (H 2 0) 2 by the solute. The thermal effect of the dissociation 

 of (H 2 0) 3 by rising temperature is modified by the presence 

 of the solute in such a way as to make the specific heat of 

 most solutions less than that given by the simple law of 

 mixtures. It is shown that (phC-^p^ — c / )/p B p 4 is of the 

 form ar/e—bp^. But here t of the negative ion does not 

 appear in arje 1 because (H 2 0) 2 is stable to rising temperature, 

 while (H 2 0) 3 is unstable. This is the fundamental fact in 

 the molecular constitution of water, and is confirmed by this 

 striking failure of the negative ion to produce an effect in 

 connexion with the term arje. The values of ar for the 

 positive ions obtained from the specific heats of solutions are 

 in a general way proportional to the values of t obtained 

 from the contraction of volume on solution. It is shown 

 that be [e is equivalent) for a compound is proportional to 

 the square of its heat of formation, a theory of this being 

 briefly sketched. The chief point in this theory is the con- 

 sideration of the intense electric field between a positive 

 and a negative ion which are near to one another without 

 being united. 



In the surface tensions of solutions the failure of the normal 

 law for mixtures is traced to the change of (H 2 0) 3 into (H 2 0) 2 

 by the solute. The amount of this change deduced from 

 surface tensions is comparable with that previously found ; 

 but the comparison is complicated by the entrance of unknowns 

 such as the solubility of solute in the surface film. 



Melbourne, April 1906. 



