68 o 
Haynes.—Diphasic Liquid Systems 
the possibility of a diffusion potential in oils—criticism was directed to the 
fact that he regards it as negligible throughout his systems. 
In the previous paper criticism was mainly directed to those systems 
which contain free acid in the oil phase. It is felt that sufficient emphasis 
was not laid upon the fact that all Dr. Beutner’s measurements of solubility 
depend upon changes of conductivity in oils saturated with water, and that 
where chlorides or salts of other mineral acid react with organic acid present 
in the oil phase, much of the increased conductivity may be due to increase 
in the concentration of hydrogen ions. For this reason it is unlikely that 
Dr. Beutner’s measurements afford any true indication of the concentrations 
of sodium ions in the £ oil ’ phase. At boundaries where the sodium salt of 
an organic acid is present this difficulty does not arise, and Dr. Beutner’s 
assumption that the change of conductivity is principally due to increase of 
sodium ions may well be justified. Since sodium ions are present in large 
excess, the interphasic potential will be determined by the solubility of the 
sodium salt; the writer’s previous criticisms on this point are therefore not 
valid. In reversible conditions the interphasic potential will be measured by 
the distribution of the sodium ion, since this is common to the two phases ; 
therefore, given reversibility, the formula holds good at this boundary ; but 
it is hardly admissible to regard such systems as reversible, and diffusion 
potentials probably contribute to the total E.M.F. 
In the original criticism it was suggested that the E.M.F. of reversible 
systems of the type 
KC 1 
Acid KC 1 
oil C 2 
may be due to a difference of hydrogen-ion concentration on either side of 
an oil phase in which hydrogen-ion concentration is constant. Dr. Beutner 
attempts to disprove this suggestion by comparing the E.M.F. of the system 
salicylic acid 
saturated solution 
oil saturated with 
salicylic acid 
salicylic acid 
KC 1 
with the pH values of the two aqueous solutions. He has, however, left out 
of consideration the fact that the equilibrium 
KCl + C 6 H 4 (OH)COOH ^ C 6 H 4 (OH)COOK + HCl 
will be disturbed by the introduction of the oil phase, which will not only 
act as a reserve of acid but will also tend to dissolve undissociated potassium 
salicylate. On both accounts the equilibrium will be displaced to the 
right, and it is probable that a very considerable increase of hydrogen- 
ion concentration will result. This, however, cannot account for the whole 
difference of potential observed in the above system, and a consideration of 
this system has drawn attention to the fact—the importance of which has 
been overlooked both by Dr. Beutner and the present writer—that potassium 
