COULTER COUNTING AND LIGHT-DIFFRACTION ANALYSIS APPLIED TO CHARACTERIZATION OF OIL-WATER EMULSIONS

Coulter counting and light diffraction techniques were successfully ap plied to the characterisation of the droplet concentration and size di stribution in camphene-water and cyclohexane-water emulsions. Both of these techniques required a dilution of the emulsion prior to analysis , and it was found that the destabilizing effect on the droplets of su ch dilution could be overcome by performing the analyses at temperatur es below the melting point of the oil phase. The storage stability of the camphene-water samples al 60 degrees C was reasonably good with a 5-20% change in the investigated parameters over a 24 h period. At roo m temperature camphene-water samples left to stand undisturbed were un affected after 24 h, while continuous mixing of the emulsion on a roll er board brought about a rapid amalgamation of the particles into larg er aggregates. This fusion process was fully described only with the l ight diffraction analysis due to the broader measuring range of this t echnique. However; analysing emulsions with a droplet size range cover ed by both techniques gave identical results. (C) 1997 Elsevier Scienc e B.V.