Chemistry Reference
In-Depth Information
2.00
1.00
0.00
0
10
20
30
40
Frequency, Hz
Fig.1.
Damping coefficient due to walls and clean water surface. Ɣ - experiment,
¸,ż, x - theory for modes 0,1,2
4.2 Wavelengths at film-covered water surfaces
Measurements of the wavelengths of standing CGW were carried out from
photographs of the wave patterns in the container. In order to reduce the
influence of the meniscus on the wavelength the wave crests/troughs dis-
tances were measured for the waves not adjacent to the container walls.
The results for CGW at a frequency of 25 Hz are shown in Figure 2.
The surface tension coefficient V for the studied films can be found eas-
ily from the dispersion relationship as follows:
V
=(
Z
2
-gk)/k
3
(3)
Corresponding film pressure values 5
=
V
0
-
V
(
*
)
as a function of surfac-
tant concentration *, calculated from the wavelength measurements are
shown in Figure 3, arrow bars are shown in the last graphic. In Figure 3 the
static elasticity values, estimated from the pressure-concentration curves as
E=
*
(dP/d
*
)
are also presented (the scale for the values of elasticity and
film pressure is the same).
