ISSN 1070-4272, Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 7, pp. 1204 !1206. + Pleiades Publishing, Inc., 2006.
Original Russian Text + O.P. Korotkikh, N.N. Kochurova, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 7, pp. 1214!1216.
Micelle Formation in Aqueous Dodecylpyridinium Chloride
O. P. Korotkikh and N. N. Kochurova
Research Institute of Chemistry, St. Petersburg State University, St. Petersburg, Russia
Received December 12, 2005; in final form, April 2006
Abstract-Micelle formation in aqueous dodecylpyridinium chloride is studied at 20, 25, 30, 35, and 40oC
using the surface tension and conductivity methods.
Physicochemical studies of surfactants are impor-
tant in view of great importance of these substances
for private life, agriculture, medicine, and a variety of
industrial processes .
In this study we examined micelle formation in
aqueous solutions of a cationic surfactant, dodecyl-
pyridinium chloride (C
Cl) (DPC), using
the surface tension and conductivity methods.
The quality of DPC used was confirmed by the
lack of a minimum in the surface tension isotherm
near the critical micelle concentration (CMC), and
also by the spectroscopic and HPLC tests. Aqueous
DPC solutions were prepared using double-distilled
The surface tension was measured by the ring
detachment method  on a digital instrument (Mar-
kada, St. Petersburg) .
The instrument was calibrated by measuring the
surface tension of hexane, isopropanol, benzene,
ethylene glycol, and double-distilled water. The cali-
bration curve was linear, allowing easy recalculation
of the readings to the surface tension. The error of
determination was within 0.5 mN m
The measurements were carried out at 20oC. The
DPC concentration was varied from 5.5 010
M. Figure 1 show that the surface tension
decreases with increasing DPC concentration, which
is typical of the surfactant solutions [1, 4]. The CMC
was determined to be 1.78 0 10
M by crossing two
straight lines obtained using the least-squares method
The conductometric measurements were carried out
on a V3-60 ac bridge at 2500 Hz, to eliminate polari-
zation. The cell was calibrated with 0.01 N KCl.
The temperature was maintained constant to within
0.05oC. The error of the conductivity determination
was within 2%.
The conductivity was measured after establishment
of the temperature and concentration equilibria. Solu-
tion preparation and all the measurements were carried
out in a temperature-controlled glass cell taking into
account the recommendations made in .
Figures 2a32e shows the concentration depen-
dences of the equivalent conductivity l = f(c
aqueous DPC of solutions at 20, 25, 35, and 40oC and
concentrations (134) 010
M. The curves follow
the general trend, i.e., the equivalent conductivity
decreases with increasing concentration [7, 8]. There
are maxima and minima in the curves, like those
reported in . The first maximum corresponds to
determined from the dependence of the specific
conductivity k on the DPC concentration, as the
1.78 0 10
ln c [M]
Fig. 1. Surface tension of DPC g at 20oC as a function of
lnc.(c) DPC concentration; the same for Fig. 2.