STRUCTURE AND DYNAMICS OF AQUEOUS ELECTROLYTE SOLUTIONS UNDER CRITICAL CONDITIONS

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1. Structure of water has been investigated over a range of 100-400 ﾟC and 50-150 MPa by novel x-ray diffractometry using an imaging plate. It has been found that hydrogen bonds decrease with increasing temperature and pressure but still remain in supercritical water.2. Li^+ and Cl^- ion hydration has been investigated near the critical point of water for solutions of LiCl in D_2O by neutron isotopic substitution method using ^0Li-^7Li and ^<35>Cl-^<37>Cl pairs. With raising temperature the ion-oxygen and ion-deuteron distances increase slightly, and the hydration numbers decrease from 4 to 3 for Li^+ and from 6 to 3 for Cl^-, suggesting the partial dehydration in the shells and the formation of ion-pairs.3. Spherical harmonic expansion method has been employed by using the neutron diffraction data, and the three dimensional view of the hydration shell of Cl^- above the critical point of water has been visuallized.4. Structure of methanol has been investigated over a range of 25-253 ﾟC and 0.1-260 MPa by imaging-plate x-ray diffraction, and it has been found that hydrogen bonds are weakened and the chain structure is distorted at supercritical temperature.