1. The effect of temperature on viscosity. The microwaves heat the
water, and heat is transferred from the water to the oil interfacial
layer. The increased temperature causes the oil viscosity to
decrease, which increases the settling velocity. The microwavepower applied to the emulsions was the same in each case;
however the water is heated selectively over the oil. If heat
transfer is neglected, an energy balance means that the lower
mass of water in the 95/5 emulsion will attain a higher temperature
than the larger mass of water in the 70/30 emulsion, but
the initial interfacial area is the same. The decrease in viscosity,
and hence increase in settling velocity, will therefore be more
marked in the lower water content emulsion.