Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 1, pp. 161−163.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © G.V. Mitrofanova, V.A. Ivanova, 2012, published in Zhurnal Prikladnoi Khimii, 2012, Vol. 85, No. 1, pp. 168−170.
Study of Dissociation of α-Alkyl-Substituted
G. V. Mitrofanova and V. A. Ivanova
Mining Institute, Kola Science Center, Russian Academy of Sciences, Apatity, Russia
Received July 15, 2011
Abstract—Dissociation of α-alkyl-substituted dicarboxylic acids low-soluble in water was studied by the method
of рН-potentiometry titration. Equilibrium constants of the dissociation at 25°С were determined.
It was shown earlier that alkyl-substituted dicarbox-
ylic acids (DA) are promising collectors for ﬂ otation of
some non-sulﬁ de ores [1, 2]. It is necessary to note in
this connection that the assortment of reagents used for
the ﬂ otation in acid medium and a possibility of their ap-
plication are rather limited. So, the activity of a fatty-acid
collector, such as oleic acid or tall oils, decreases at рН <
5 in view of a low dissociation degree. The presence of the
second carboxyl group in a collector molecule appreciably
inﬂ uences its acid properties and, hence also its activity
in the acid-medium ﬂ otation. For this reason the study of
dissociation of α-alkyl-substituted dicarboxylic acids is
an important stage in studying their ﬂ oatation operation.
Acid-base properties of carboxylic collectors are
poorly studied, and available published data are rather
conﬂ icting. So, values of the dissociation constants for
oleic acid determined by various authors differ by several
orders: рK 4.95  and рK 9.80 . There are data on the
dissociation of some α-alkyl-1,1-1,3-dicarboxylic acids
with rather small hydrocarbon radicals from –С
. The procedure used for their determination 
is based on the graphical determination of the constants
from the data of the potentiometric titration of an acid
aqueous solution by an alkali solution. In view of a low
solubility of the acids under consideration in water such
procedure can lead to erroneous results.
The aim of this work was to study acid-base properties
of some α-alkyl-dicarboxylic acids low-soluble in water
with hydrocarbon radicals from –С
up to –С
and with 1,1-1,7-arrangement of carboxyl groups.
Difﬁ culty of studying physicochemical properties of
carboxylic collectors is caused by their low water solu-
bility. Therefore we used the procedure of dissociation
constants determination by potentiometric titration of a
series of water-alcohol solutions of dicarboxylic acids
with various water-alcohol ratios (70 : 30, 50 : 50, 30 :
70, 20 : 80) by alkali followed by extrapolation of the
resulting linear dependences to a zero alcohol content.
The preliminary test of the procedure by the example
of α,ω-dicarboxylic acids has shown a good agreement
between calculated dissociation constants and published
We have studied dissociation of a series of α-alkyl-
dicarboxylic with the common formula
Here R is an alkyl radical from С
up to С
m = 1–7.
All the compounds were preliminary purified by
recrystallization from benzene or ethanol and dried up
under a reduced pressure.
Measuring рН of the systems under study was carried
out with a glass electrode and an I-120.1 ionometer accu-
rate to 0.02 at 25°С and an ionic strength of 0.1 provided
by potassium chloride. For the titration we used KОН
water–alcohol solution with a speciﬁ ed water:ethanol ra-