Emulsions, Microemulsions, and Lyotropic Liquid Crystals - Surface and Colloid Chemistry: Principles and Applications - page 178

table 9.4
hlb Group numbers

Group Group number

hydrophilic

-SO 4 Na 39

-COOH 21

-COONa 19

Sulfonate 11

Ester 7

-OH 2

lipophilic

-CH 0.5

-CH 2 0.5

-CH 3 0.5

-CH 2 CH 2 O 0.33

could be found from animal testing, which determines the amount of a substance
that causes 50% (or more) of the test animals to die (lethal dosage; LD 50 ). For this
reason, food emulsions are subject to very strict controls (Friberg, 1976).

9.2.2 m e T h o d S of f e m u l S I o n f o r m a T I o n
If one shakes oil and water, the oil breaks up into drops. However, they will quickly
coalesce and return to the original state of two different phases. The longer one
shakes, more drops reduce in size. In other words, the energy put into the system
makes the drops smaller in size.
Emulsions are made based on different procedures. One is the use of mechani-
cal agitation. Other methods are also used. The emulsion technology is very much
a state-of-the-art type of industry (Sjoblom et al., 2008; Friberg, 1976; Holmberg,
2002; Birdi, 2002). Therefore, there exists a vast literature about methods used for
any specific emulsion. In a simple case, an emulsion may be based on three neces-
sary ingredients: water, oil, and emulsifier. In other words, one needs to determine
in which weight proportions one need to mix these substances in order to obtain an
emulsion (at a given temperature) to be stable (or maximum stability). This may be
more conveniently carried out in a phase study in the triangle. The micellar region
exists on the water-surfactant line (Figure 9.2).
Near the surfactant region the crystalline or lamellar phase is found. This is the
region one finds in hand soaps. The ordinary hand soap is mainly the salt of fatty
acid (coconut oil fatty acids or mixtures [85%] plus water [15%] and some salts.
X-ray analyses have shown that the crystalline structure consists of a layer of soap
separated by a water layer (with salts). The hand soap is produced by extruding under
high pressure. This process aligns the lamellar crystalline structure lengthwise. If
the degree of expansion versus temperature is measured, the expansion will be found