[miller-kenrick] researches IN PHYSICAL CHEMISTRY 217 



results were carried out by placing electrodes in solutions where iodide 

 and iodine were in equilibrium with ferric and ferrous salts, or with 

 arsenic and arsenious acids. {Winter 1912-1913). 



No. 25. K. E. Burgess: — The toxicity of solutions conUiining 

 phenol and sodium benzoate. Using the stain method (referred to 

 under Mr. Eraser's name above) as a guide, Mr. Burgess studied the 

 effect of pure water, sodium benzoate solutions, and solutions con- 

 taining both phenol and sodium benzoate on micrococcus pyogenes. 

 His results furnish a satisfactory confirmation of the explanation 

 given above (see Laird) for the ''abnormal" effect of salts in very 

 dilute phenol solutions. {Winter 1912-1913). 



No. 26. N. J. Ireland: — The yiature of the cathodic silver deposit. 

 A series of microphotographs were made of the silver deposited from 

 silver nitrate solution, wath different current densities, concentrations, 

 temperatures, and rates of stirring. Preliminary determinations of 

 the "limiting current" made it possible to plan the experiments so that 

 each differed from the next in one respect only, e.g., either in con- 

 centration at the electrode, or in current density, not in both together, 

 as has been the case in previous work. {Winter 1912-1913). 



No. 27. Frank B. Kenrick and R. L. McGregor: — Thickness of 

 the surface layer in solutions of surface active substances. From the change 

 of the surface tension with the concentration of a dilute solution it is 

 possible to calculate, by Gibbs' equation, the ''surface accumulation" 

 of dissolved substance per unit area of surface. If the concentration 

 of the dissolved substance in the surface layer were known and if an 

 assumption were made as to the law according to which the concen- 

 tration changes in a direction normal to the surface, the order of 

 magnitude of the thickness of the surface layer could be calculated. 

 In order to obtain information as to the concentration of the surface 

 layer, some property of that layer must be measured, and the value 

 compared with the corresponding values for solutions of known con- 

 centration. 



Two properties suggested themselves as suitable for this purpose: — 

 {i) the surface tension of the liquids, {ii) the critical angle of reflection, 

 from which it was hoped the refractive index of the surface layer might 

 be obtained. A measurement of the surface tension of the liquiti by 

 one of the static methods gives the value of this property for the sur- 

 face layer of composition corresponding to equilibrium; while the de- 

 termination of the surface tension by the oscillating jet method gives 

 the value of this property when the composition of the surface ap- 

 proaches that of the body of the liquid, whose concentration is known. 

 It was hoped that a comparison would lead to an estimate of the con- 

 centi'ation of the surface layer. 



" Sec. Ill, 1913—14 



