Chapter 2
an organic liquid as W∕O. For W∕O emulsions, water is considered the dispersed
or internal phase, and oil is the continuous or external phase, and conversely for
the O∕W type. Multiple emulsions such as O∕W∕O or W∕O∕W emulsions are also
present in some cases.
2.2. Properties Ofemulsions
2.2.1. Drop size distribution
A population of emulsions is described by emulsion drop size distribution.
The corresponding drop size distribution is a statistical inventory of the
disaggregation of the dispersed phase. Drop size distribution can be expressed
as frequency distribution curves or cumulative curves.
Among various drop size distributions, log-normal distribution function
describes well drop sizes in emulsions [3]. Studies on solid grinding [4] and
emulsification with turbulent stirring [5] show that breakup sequences of drops lead
to such distribution.
[ln(rf)-ln(⅜)]2
p(rf)= ɪ e 2°'∙ [2.1]
y∣2πdσg
Here d is the drop diameter, dg is the geometric mean drop size and σg is the
geometric standard deviation of the distribution.
In some other cases, lognormal distribution is not observed. The drop size