Dielectric relaxation of dilute aqueous NaOH, NaAl(OH)4 and
NaB(OH)4
R. Buchner, G.T. Hefter, P.M. May, and P. Sipos
J. Phys. Chem. B 103 (1999) 11186-11190
Abstract
The complex dielectric permittivity of aqueous NaOH (c >= 2M), and of dilute
(<= 0.6 M) NaAl(OH)4 and NaB(OH)4 solutions in NaOH ([Na] = 1M) at 25
C
has been determined in the frequency range 0.2 <= n/GHz <= 20.
All spectra could be represented by a single Cole-Cole relaxation time distribution attributed to the cooperative relaxation
of the solvent. The concentration dependence of the effective hydration number
of OH- has been determined. For aluminate
and borate solutions the deduced parameters, effective conductivity ke,
static permittivity e, relaxation time t, and distribution parameter
a, suggest a 1:1 replacement of hydroxide by aluminate and borate, accompanied by a release of bound water.
The lack of an ion-pair relaxation process despite notable ion association suggests that rapid proton exchange is not only important for
the dynamics of OH-, but also for Al(OH)4- and
B(OH)4-.
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(c) 1999 Herbert Poepke
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