Apparent molar volumes for dilute solutions of NaClO₄ and [Co(en)₃] (ClO₄)₃ in D₂O and H₂O at 278-318 K

Abstract

Apparent molar volumes for dilute solutions of NaClO₄ and [Co(en)₃] (ClO₄)₃ in D₂O and H₂O were measured by using a dilatometry technique at 278, 298 and 318 K. Comparison of limiting slopes with the Debye-Huckel predictions from the dielectric constant and compressibility of H₂O and D₂O is complicated by ion pairing. The apparent molar volumes for NaClO₄ were less in D₂O than in H₂O. The complex [Co(en)₃] (ClO₄)₃ when studied in D₂O had its amine protons exchanged by deuterium; this did not allow a direct comparison of the apparent molar volumes of the protonated complex in each solvent system, but revealed a large isotope effect. The apparent molar volumes of the [Co(en)₃] (ClO₄)₃ showed a much larger temperature dependence than that of NaClO₄.