Precise sound speed measurements on concentrated aqueous solutions of LiCl, MgCl2, CaCl2, SrCl2, and BaCl2 show positive transitions. These transitions occur respectively at 10.7 ± 0.7, 3.8 ± 0.6, 5.9 ± 0.5, 2.1 ± 0.2, and 0.9 ± 0.4 m for LiCl, MgCl2, CaCl2, SrCl2, and BaCl2 solutions. No transitions were found in the densities of these solutions. These transitions may be attributed to changes in the hydration structure around the cations. Since the sound speeds increase, the adiabatic compressibilities and partial molal compressibilities will decrease at the transition. This would lead to an increase in the hydration numbers, if one uses a simple model for the water structure around the ions.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry