Interfacial Area Measurement Using a Radioisotope Technique

Abstract

<p> A radioactive technique to determine interfacial area between solid-liquid and liquid-liquid phases has been investigated. Plastic and liquid scintillators and β-particles from tritium solution were used for this purpose.</p> <p> The tritium β-particles have a very short range (about 5 μm in water), and the surface area of contact between the tritium bearing fluid and the scintillator bearing phase is expected to be proportional to the scintillation count rate, which in turn is proportional to the number of betas crossing the interface from a very thin region.</p> <p> To test this hypothesis, two phases were placed together in a cylindrical plexiglas container, which in turn was placed in an aluminum light-tight housing. The housing also enclosed the photo-multiplier tube (PMT). Pulses corresponding to scintillations due to β absorption were taken from the PMT and fed to a suitable electronic circuit. The count rate was obtained with a multi-channel analyser.</p> <p> It was found that the count rate is a linear function of interfacial area between the tritium bearing fluid and the scintillating material. Some deviation from linearity was however noticed at very low tritium concentration. The count rate remained the same for a given interfacial area regardless of orientation of the surface(s) with respect to the photocathode face.</p> <p> This appeared to confirm the hypothesis that interfacial area could be measured in systems of this type by measuring the scintillation count rate.</p>