Capillarity and Surface Forces (Liquids) - Surface and Colloid Chemistry: Principles and Applications - page 37

table 2.3
antonow's rule and Interfacial tension
data [mn/m]

oil Phase w(o) o(w) o/w w(o)-o

Benzene 62 28 34 34

Chloroform 52 27 23 24

Ether 27 17 8 9

Toluene 64 28 36 36

n -Propylbenze 68 29 39 40

n -Butylbenzne 69 29 41 40

Nitrobenzene 68 43 25 25

i i-Pentanol 28 25 5 3

n -Heptanol 29 27 8 2

CS 2 72 52 41 20

Methyleneiodide 72 51 46 22

Note: See text for details.

γ water = 72 mN/m (at 25°C),

γ hexadecane = 20 mN/m (at 25°C)

γ water-hexadecane = 72 − 20 = 52 mN/m (measured = 50 mN/m) (2.53)

However, for general considerations, one may only use it as a reliable guideline and
when exact data are not available.
Antonow's rule can be understood in terms of a simple physical picture. There
should be an adsorbed film or Gibbs monolayer of substance B (the one of lower
surface tension) on the surface of liquid A. If we regard this film as having the prop-
erties of bulk liquid B, then γ A(B) is effectively the interfacial tension of a duplex
surface and would be equal to [γ A(B) + γ B(A) ].

2.7.2.4 measurement of Interfacial tension
(between two Immiscible liquids)
IFT can be measured by different methods, depending on the characteristics of the
system. The following are some of them:

Wilhelmy plate method
Drop weight method (can also be used for high pressure and temperature)
Drop shape method (can also be used for high pressure and temperature)

The Wilhelmy plate is placed at the surface of the water, and the oil phase is added
until the whole plate is covered by the latter. The apparatus must be calibrated with
known IFT data such as water-hexadecane (52 mN/m; 25°C) (Table 2.4).