X-ray Phase Analysis of Structure of Water-Salt Systems: NaCl-H₂O and KCl-H₂O

The Opposite Effect of Metal Ions on Short-/Long-Range Water Structure: A Multiple Characterization Study

“…From Figure 5 , the content of high association water declined consistently with salt concentration, while the content of low association water increased rapidly before 200 mmol·L −1 and then decreased with salt concentration. The decrease in the amount of low association water, as pointed out by Pestova et al [ 10 ] and O’Brien and Williams [ 12 ], is due mainly to the overlap of hydration layer with the continuous increase in metal ion concentration. However, the addition of the electrolytes promotes the decrease in association degree, which is in contrast to the regularities obtained from NMR and viscosity measurements and needs to be further discussed.…”

“…In addition to HB dynamics, static water structures have also been determined to study the metal ion-induced effects. An X-ray diffraction study suggested that the KCl unit in aqueous solution could control 45 water molecules to form rigid spherical structure [ 10 ]. Another neutron diffraction study provided compelling evidence that Ca 2+ could have an impact on the hydrogen structure in the second hydration shell [ 11 ].…”

Changes of Water Hydrogen Bond Network with Different Externalities

“…The ion-dependent changes in water structure could be observed by spectrum study with varying ion concentration. An X-ray diffraction study observed the number of water molecules around KCl unit in aqueous solution was 45, with which clathrate like spherical structure formed [ 120 ], and based on topology, the KCl unit could influence more than three hydration layers. In 2012, Suresh et al [ 121 ] used statistical mechanics to probe into the structure changes induced by cations and found the cation-induced changes in molecular orientation and non-linear polarization effects could persist up to ~3–4 hydration layers in the case of low charge density ions, and ~7–9 layers for high charge density ions.…”

TrimethylamineN-oxide (TMAO) resists the compression of water structure by magnesium perchlorate: terrestrial kosmotropevs.Martian chaotrope

“…Its maximum density at 4 o C, unusually high heat capacity and low compressibility are examples of these. The response of the hydrogen bonded loosely packed network of liquid water to solutes such as ions and amphiphilic molecules has been examined in depth by techniques such as Raman(6,7), IR spectroscopy (8)(9)(10)(11)(12)(13)(14), molecular dynamics simulations (15)(16)(17)(18)(19)(20)(21)(22), NMR(23), X-ray diffraction (24,25) and neutron diffraction (26)(27)(28)(29)(30)(31)(32)(33), which has allowed us to visualise structure making (kosmotropic) and structure breaking (chaotropic) effects. One of the most striking results is the modification to water structure as a result of ion addition, which is often similar to that of pure water under pressure (29,30).…”