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Dielectric relaxation of dilute aqueous NaOH, NaAl(OH)4 and NaB(OH)4
Journal article   Peer reviewed

Dielectric relaxation of dilute aqueous NaOH, NaAl(OH)4 and NaB(OH)4

R. Buchner, G. Hefter, P.M. May and P. Sipos
Journal of Physical Chemistry B, Vol.103(50), pp.11186-11190
1999
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Abstract

The complex dielectric permittivity of aqueous NaOH (c ≤ 2 M) and of dilute (≤0.6 M) NaAl(OH)4 and NaB(OH)4 solutions in NaOH ([Na] = 1 M) at 25°C has been determined in the frequency range 0.2 ≤ v/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 ε, relaxation time τ, 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 important not only for the dynamics of OH- but also for Al(OH)4- and B(OH)4-.

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