The adsorbability of dyestuffs at the oil-water interface, and the influence of inorganic electrolytes on it, were investigated by measuring electrocapillary curves. The oil phase was the solution of a surface inactive organic electrolyte in methylisobutylketone, and the aqueous phase contained various dyestuffs in addition to the inorganic electrolyte.
It was found that the interfacial tension decreased over the anodic or cathodic polarization range, depending upon whether the dyestuff was anionic or cationic. In addition, this decrease was strongly influenced by the kind and concentration of the electrolyte in the aqueous phase.
For the same kind of dyestuffs, the surface activity increased by decreasing “Inorganic-Organic Balance”, proposed by Fujita, and a linear relation held between the decrease in interfacial tension and this “Balance”, with the slope -3.5.
A linear relation held between the net interfacial excess concentration of dyestuff and the cubic root of the dyestuff concentration in the aqueous phase, which was in good agreement with Davies' deduction.
This adsorbability of dye at the oil-water interface was found to correspond to the amount of dye actually absorbed by 6 Nylon fibres.
