The addition of CaCl2 to the emulsion significantly
altered the extent of droplet aggregation. When the
CaCl2 concentration was increased from 0 to 1 mM the
pH at which the droplets aggregated shifted to higher
values (Fig. 3). This is because the isoelectric point of
the emulsion droplets shifted to higher pH (Fig. 1),
presumably because of binding of Ca2+ ions at very low
calcium chloride concentrations. As the CaCl2 concentration was increased above 1mM the range of pH
values above the isoelectric point over which the emulsions became unstable grew wider. At 20 mM CaCl2 the emulsions were unstable to aggregation at all pH values
above the isoelectric point.