Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 1, pp. 79−83.
Pleiades Publishing, Ltd., 2011.
Original Russian Text © K.N. Semenov, D.G. Letenko, N.A. Charykov, V.A. Nikitin, M.Yu. Matuzenko, V.A. Keskinov, V.N. Postnova, A.A. Kopyrin, 2011,
published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84, No. 1, pp. 79−83.
AND CORROSION PROTECTION OF METALS
Electrochemical Properties of Aqueous Solutions
K. N. Semenov
, D. G. Letenko
, N. A. Charykov
, V. A. Nikitin
, M. Yu. Matuzenko
V. A. Keskinov
, V. N. Postnov
, and A. A. Kopyrin
St. Petersburg State University, St. Petersburg, Russia
Innovations at Leningrad Institutes and Enterprises, Private Company, St. Petersburg, Russia
Northwestern State Technical University, St. Petersburg, Russia
St. Petersburg State Technological Institute, St. Petersburg, Russia
Received March 4, 2010
Abstract—Dependence of the pH value on the concentration of fullerenol solutions was studied by means of pH-
potentiometry, and the apparent degree of dissociation and the dissociation constant of fullerenol were calculated.
The dependence of the electrical conductivity of fullerenol solutions on their concentration was examined. The
molar electrical conductivity and also the apparent degree of dissociation and the dissociation constant of fullerenol
Previously, we have developed a procedure for
synthesis of fullerenol, identiﬁ ed fullerenol-d by
physicochemical methods, determined the solubility and
other properties of aqueous solutions of fullerenol-d,
and found the composition of its crystal hydrates [1, 2].
Our present study is concerned with the electro-
chemical properties of aqueous solutions of fullerenol-d.
The pH value of aqueous solutions of fullerenol-d
was determined by pH-potentiometry , using a Delta
320 pH-meter with a “three-in-one” InLab413 electrode
(IP 67) with an accuracy ΔpH of 0.05 rel. units.
Measurements were made in air at room temperature,
T = 22 ± 2°C.
Figure 1a shows the dependence of the pH value
of aqueous solutions of fullerenol-d on its molar
). It can be seen that fullerenol-d
solutions exhibit a pronounced alkaline reaction.
Consequently, the alcoholic (acid) dissociation
mechanism of the type
is inoperative. Thus, the very name of the compound,
“fullerenol” (with the alcoholic sufﬁ x “-ol”), seems to
be incorrect, although being commonly accepted. We
are forced to suggest the basic dissociation mechanism
which accounts for the observed effect.
Also noteworthy is that even the most dilute of the
fullerenol-d solutions studied (with M
≈ 00013 M)
strongly alkalize aqueous solutions: pH(M
0.00013 M) ≈ 9.95 rel. units. Further, with increasing
, the rate at which pH grows decreases and stabilizes.
Figure 2a plots the dependence of the apparent degree
of fullerenol-d dissociation on the solution molarity,
). An evaluating calculation was performed
under the following simplifying assumptions: excess
thermodynamic functions (activity coefﬁ cients) of
hydroxide ions (a
, where a
, and M
are the activity and molarity of OH
) are disregarded;
fullerenol-d dissociates only by the ﬁ rst stage [Eq. (1)],