  We propose an improved viscosity model accounting for experiments of
emulsions of two immiscible liquids at arbitrary volume fractions and low shear
rates. The model is based on a recursive-differential method formulated in
terms of the appropriate scaling variable which emerges from an analysis of
excluded volume effects in the system. This variable, called the effective
filling fraction, incorporates the geometrical information of the system which
determines the maximum packing and reduces to the bare filling fraction for
infinitely diluted emulsions. The agreement of our model for the viscosity with
experiments is remarkable for all the range of volume fractions and viscosity
ratio.
