Growing Negative Pressure in Dissolved Solutes: Raman Monitoring of Solvent-Pulling Effect

Abstract

International audienceNegative pressure in liquids is both an experimental fact and a usually-neglected state of condensed matter. Using synthetic fluid inclusions, namely closed vacuoles fabricated inside one solid host by hydrothermal processes, a Raman study was performed to examine how a superheated solvent (under negative pressure) interacts with its dissolved solutes. As a result, this contribution not only illustrates this well-known tensile state, but also displays evidence that a stretched solvent is able to pull on its dissolved solutes and put them also under a stretched state. The dielectric continuum hypothesis may lead to expect a stretching effect in solutes similar to the solvent’s, but our measurements evidence a damping mechanical effect (growing with tension), most probably related to solvation shells. One practical consequence is that the (experimentally known) super-solvent properties of superheated solutions are certainly related to the change of the chemical potential of solutes which results from the damping effect. This change can determine as well a change in the thermodynamic driving force of the superheated solution towards bubble nucleation. A more complex than usual picture of the aqueous solution physical chemistry emerges from this study

Oversolubility in the microvicinity of solid–solution interfaces

“…Eventually, any scientific area related to the stability and evolution of the chemical properties in water-containing cavities 62 , or interested to use water as a green solvent, may benefit from these results.…”

Regeneration of capillary water in unsaturated zones

“…One such assumption of such a calculation is that the pressure of each dissolved solute is equal to the pressure of liquid solvent, which is clearly a simplification (e.g., Mercury et al, 2016). The pressure dependency of ion volumes at infinite dilution are taken from Tanger and Helgeson (1988), and the pressure effect on the activity coefficient is overlooked, which does not afford a significant error (e.g., Lassin et al, 2005).…”

High‐sensitivity Raman imaging of the surface of casted glass plates

“…All measurements were recorded at room temperature. The frequency and intensity stability of the device are improved by specific temperature control of the whole spectrometer room, leading to a stability frequency better than 0.1 cm −1 over 24 h [15] …”

“…All measurements were recorded at room temperature. The frequency and intensity stability of the device are improved by specific temperature control of the whole spectrometer room, leading to a stability frequency better than 0.1 cm −1 over 24 h. [15] During the acquisitions, the focus was set 10 μm below the surface to minimize surface effects. In addition, we used Renishaw's LiveTrack™ focus tracking feature to accommodate the curviness of the casted samples.…”