DIRECT AND ELECTRICAL-CONDUCTIVITY MEASUREMENTS OF THE LIQUID CONTENTS IN STEADY-STATE FOAMS

The liquid content in foam formed from n-pentanol solutions under steady-state conditions was determined by two independent methods: an electrical conductivity method and a direct method. The latter consists of the cutting-off of a chosen foam layer using a specially constructed column and weighing the solution obtained from the cut-off foam layer. The electrical conductivity method is based on measuring the electrical conductivities of the same layers of the foam and the bulk solution. The ratio of the conductivities is proportional to the liquid content in the foam layer. The accuracy of the electrical conductivity method depends on the value of the proportionality coefficient B. The values of B, obtained from the liquid content data obtained by the direct method were compared with the values calculated from semi-theoretical Lemlich and Maxwell relationships used in the electrical conductivity method. It was found that values of the coefficient B calculated from the Lemlich and Maxwell relationships were in reasonable, but not fully satisfactory, agreement with those obtained from measurements by the direct method. Nevertheless, the results obtained indicate that the more convenient electrical conductivity method can also be applied in investigations of steady-state foams,