TY - JOUR
T1 - Measurement of the dielectric relaxation property of water-ion loose complex in aqueous solutions of salt at low concentrations
AU - Miyazaki, Takashi
AU - Mogami, George
AU - Wazawa, Tetsuichi
AU - Kodama, Takao
AU - Suzuki, Makoto
PY - 2008/10/30
Y1 - 2008/10/30
N2 - Electrolytes and their dissociated ions are thought to form positive or negative hydration layers around them. In this study, we have developed a method to determine the volume and the dielectric relaxation property (relaxation frequency fc, dispersion intensity δ) of the water hydrating ions in salt solutions. The method consists of four steps: (1) By use of a high-resolution microwave dielectric spectroscopy technique, the dielectric spectra of sample salt solution and bulk water are measured in pair. (2) The dielectric spectrum of solutes (ions) with water layers for a given volume fraction φ is then calculated from each pair of dielectric spectra of a sample salt solution and reference water according to the Hanai mixture theory. (3) Each spectrum of solutes with water layers at a given 0 is decomposed into a few Debye relaxation functions and the bulk water component. (4) The volume fraction φ is operationally decreased from 0.5, and steps (2) and (3) are repeated at each φ until the bulk water component vanished. Then the volume fraction of the hydrated solutes (ions) in solution is determined. The method was applied to NaF and NaCl solutions. As a result the different spectral intensity was nearly proportional to the salt concentration below 0.2 M in the frequency range of 3-26 GHz. The hydration number Nh, and the dielectric relaxation property of the hydration layer for each salt solution was successfully determined as (fcl, δ1, N h)= (18.7, 44.9, 27.9) for NaCl and (fcl, δ1, fc2, δ2, Nh) = (26.0, 6.70, 5.64, 19.2) for NaF.
AB - Electrolytes and their dissociated ions are thought to form positive or negative hydration layers around them. In this study, we have developed a method to determine the volume and the dielectric relaxation property (relaxation frequency fc, dispersion intensity δ) of the water hydrating ions in salt solutions. The method consists of four steps: (1) By use of a high-resolution microwave dielectric spectroscopy technique, the dielectric spectra of sample salt solution and bulk water are measured in pair. (2) The dielectric spectrum of solutes (ions) with water layers for a given volume fraction φ is then calculated from each pair of dielectric spectra of a sample salt solution and reference water according to the Hanai mixture theory. (3) Each spectrum of solutes with water layers at a given 0 is decomposed into a few Debye relaxation functions and the bulk water component. (4) The volume fraction φ is operationally decreased from 0.5, and steps (2) and (3) are repeated at each φ until the bulk water component vanished. Then the volume fraction of the hydrated solutes (ions) in solution is determined. The method was applied to NaF and NaCl solutions. As a result the different spectral intensity was nearly proportional to the salt concentration below 0.2 M in the frequency range of 3-26 GHz. The hydration number Nh, and the dielectric relaxation property of the hydration layer for each salt solution was successfully determined as (fcl, δ1, N h)= (18.7, 44.9, 27.9) for NaCl and (fcl, δ1, fc2, δ2, Nh) = (26.0, 6.70, 5.64, 19.2) for NaF.
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U2 - 10.1021/jp802757q
DO - 10.1021/jp802757q
M3 - Article
C2 - 18837496
AN - SCOPUS:55949084530
VL - 112
SP - 10801
EP - 10806
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
SN - 1089-5639
IS - 43
ER -