Dielectric Relaxation of Dilute Aqueous NaOH, NaAl(OH)4, and NaB(OH)4

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 ≤ ν/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 κ e, static permittivity ε, relaxation time τ, and distribution parameter α 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 - .