Emulsions, Microemulsions, and Lyotropic Liquid Crystals - Surface and Colloid Chemistry: Principles and Applications - page 179

Octanol

L2

L1

Water Potassium Caprate

(a)

Surfactant

Surfactant
Rich

Micellar

Emulsions

Water Oil

(b)

FIGure 9.2 (a) Different phase equilibria in a water-surfactant (emulsifier)-oil mixture
system (schematic). (b) Phase diagram for the system: K-caprate (PK) + water + n -octanol
(22°C). All compositions are given in weight %. (L1 = micellar phase; L2 = reverse micelle;
H1 = hexagonal LC phase [shaded]).

to be twice as much along the length than along the width. It is further seen that com-
plex structures are present in the other regions in the phases (Figure 9.2). It is seen
from the diagram that the process is strongly dependent on temperature; therefore,
such studies are carried out at different temperatures.
The actual procedure is as follows. A suitable number of test samples (more than
50) are prepared by mixing each component in varying weights to represent a com-
parable number of regions (around 50 samples). The test samples are mixed under
rotation in a thermostat over a few days to reach equilibrium. The samples are then
centrifuged and the phases are analyzed. From these analyses, the phase structures
are determined. They are then investigated using a suitable analytical method.
It is obvious that studies of multicomponent systems will lead to a very large num-
bers of phases. However, by analyzing a typical system, some trends can be found
that can be used as guidelines.
A historically well-investigated system consists of water, potassium caprate
(K-caprate), and n -octanol. The phases were determined as indicated in Figure 9.2a.