A mobile gas-water interface in electrolyte solutions

The effect of a range of electrolytes on the mobility of the gas-aqueous solution interface has been investigated. By measuring the terminal rise velocity of small bubbles (diameter < 100 mu m, Re < 1) in electrolyte solutions devoid of surface active contaminants, we determined that they obey the Hadamard-Rybczynski model, corresponding to a mobile interface (slip boundary condition), in agreement with observations in pure water. In addition, there is no difference in the interfacial mobility between electrolytes that inhibit bubble coalescence relative to pure water and electrolytes that have no effect. This is strong evidence against the hypothesis that electrolytes inhibit bubble coalescence via immobilization of the interface in the absence of surface-active contaminants.