A High‐Pressure NMR Probe for Aqueous Geochemistry
TL;DR: The inexpensive probe design doubles the current pressure range available for solution NMR spectroscopy and is particularly important to advance the field of aqueous geochemistry.
Abstract: A non-magnetic piston-cylinder pressure cell is presented for solution-state NMR spectroscopy at geochemical pressures. The probe has been calibrated up to 20kbar using insitu ruby fluorescence and ...
Citations
More filters
TL;DR: In situ UV-Vis spectroscopy study demonstrated that the equilibrium constant increases with the increasing pressure, from which it is proposed that the negative volume of reaction determined the isomerization under high pressure.
68 citations
01 Jan 2018
TL;DR: A review of the basic principles of generating pressures in excess of 1 GPa (= 10.000 atm) is presented in this paper, followed by a summary of suitable NMR resonators.
Abstract: Implementation of nuclear magnetic resonance in high pressure vessels is among the most demanding technological endeavours of the field, owing to inherently low signal amplitudes, low sensitivities of the resonator set-ups, and samples which are both difficult to handle and to access in the finished experimental set-up. The following chapter presents a review of the basic principles of generating pressures in excess of 1 GPa (= 10.000 atm), followed by a summary of suitable NMR resonators. Additionally, recent high pressure experiments on correlated and uncorrelated electronic system at pressures as high as 30 GPa will be covered.
29 citations
TL;DR: In this article, the authors present the background needed to carry out theoretical geochemical modelling of fluids and fluid-rock interactions from surficial conditions into the upper mantle, and a description of the general criteria for predicting equilibrium and non-equilibrium chemical reactions is followed by a summary of how the thermodynamic activities of species are related to measurable concentrations through standard states and activity coefficients.
Abstract: Carbon is subducted to depths where metamorphism liberates water-bearing fluids. The C-bearing fluids facilitate partial melting of the upper mantle, generating magmas that may erupt as arc volcanics. Degassing of the magmas releases CO2 and other volatile species to the atmosphere. Over geological time, this process contributes to the composition of the atmosphere and planetary habitability. Here I summarize the background needed to carry out theoretical geochemical modelling of fluids and fluid–rock interactions from surficial conditions into the upper mantle. A description of the general criteria for predicting equilibrium and non-equilibrium chemical reactions is followed by a summary of how the thermodynamic activities of species are related to measurable concentrations through standard states and activity coefficients. Specific examples at ambient conditions involving dilute water are detailed. The concept of aqueous speciation and how it can be calculated arises from this discussion. Next, I discuss how to calculate standard Gibbs free energies and aqueous activity coefficients at elevated temperatures and pressures. The revised Helgeson–Kirkham–Flowers equations of state are summarized and the revised predictive correlations for the estimation of equation of state coefficients in the Deep Earth Water (DEW) model are presented. Finally, the DEW model is applied to the solubility and speciation of aqueous aluminium.
26 citations
Cites background from "A High‐Pressure NMR Probe for Aqueo..."
...Nuclear magnetic resonance (NMR) studies are now being extended to high-density fluids with the potential to help identify the nature of metal complexes (Pautler et al. 2014; Ochoa et al. 2015; Augustine et al. 2017)....
[...]
...2018), new high-pressure experimental NMR studies of aqueous species (Pautler et al. 2014; Augustine et al. 2017), and the predictions of ab initio molecular dynamics for aqueous complexing reactions (Mei et al....
[...]
...…and speciation experiments (Huang 2017; Tumiati et al. 2017; Tiraboschi et al. 2018), new high-pressure experimental NMR studies of aqueous species (Pautler et al. 2014; Augustine et al. 2017), and the predictions of ab initio molecular dynamics for aqueous complexing reactions (Mei et al. 2018)....
[...]
TL;DR: A new NMR probe designed for solution spectroscopy at geochemical pressures allows experiments on aqueous solutions to pressures corresponding roughly to those at the base of the Earth's continental crust.
Abstract: Nuclear spin relaxation rates of (2) H and (139) La in LaCl3 +(2) H2 O and La(ClO4 )3 +(2) H2 O solutions were determined as a function of pressure in order to demonstrate a new NMR probe designed for solution spectroscopy at geochemical pressures. The (2) H longitudinal relaxation rates (T1 ) vary linearly to 1.6 GPa, consistent with previous work at lower pressures. The (139) La T1 values vary both with solution chemistry and pressure, but converge with pressure, suggesting that the combined effects of increased viscosity and enhanced rates of ligand exchange control relaxation. This simple NMR probe design allows experiments on aqueous solutions to pressures corresponding roughly to those at the base of the Earth's continental crust.
17 citations
TL;DR: In this paper, an experimental approach in conducting NMR measurements at supercritical parameters of state is discussed, where a novel design of the high-pressure NMR cell was developed which allowed eliminating the field inhomogeneity and, thus, increasing the sensitivity of the experiment at the supercritical state.
17 citations
References
More filters
TL;DR: In this article, the pressure dependence of the R1 ruby fluorescence line has been calibrated at 25°C against the compression of NaCl using the Decker equation of state for NaCl.
Abstract: The pressure dependence of the R1 ruby fluorescence line has been calibrated at 25 °C against the compression of NaCl. Pressures are determined using the Decker equation of state for NaCl. The dependence is linear to 195 kbar following the equation PNaCl=2.746(Δλ), where P is in kbar and Δλ in A. The uncertainty in the value of the slope, dp/dλ, expressed in terms of a 95% confidence interval is 2.746±0.014 kbar A−1. The coefficient of the quadratic term (Δλ)2 is not significantly different from zero; and the quadratic term makes indeed a negligible contribution to the fit. Taking into account the reported uncertainty associated with the Decker equation of state for NaCl, the value of the slope is 2.740±0.016 kbar A−1 within a 95% confidence interval.
1,681 citations
TL;DR: In this paper, the modified Bloch equations for nuclear magnetic resonance are modified to describe the magnetic resonance of a single nuclear species X which is transferred back and forth between two (or more) magnetic environments (A,B) by kinetic molecular processes.
Abstract: The Bloch equations for nuclear magnetic resonance are modified to describe the magnetic resonance of a single nuclear species X which is transferred back and forth between two (or more) magnetic environments (A,B) by kinetic molecular processes. The modified Bloch equations involve the usual assumptions of the Bloch theory and, in addition, require (a) that the X nuclear relaxation times be independent of the molecular exchange rates, and (b) that the X nuclear magnetization in A relax independently of the X magnetization in B, and vice versa. The modified Bloch equations are easily solved in the slow passage case, with arbitrary rf saturation. Earlier relations between reaction rates, and resonance line shapes, which were developed by Gutowsky, McCall, and Slichter, and extended by a number of other investigators, are easily derived using the modified Bloch equations. In the present work the modified equations are used to show how rapid exchange rates can sometimes be measured in solutions where the X r...
1,453 citations
TL;DR: The role played by the relaxation time of nuclear induction has been investigated experimentally as discussed by the authors, with the results showing that it varies between about 10 − 5 − 5 seconds and many seconds.
Abstract: The phenomenon of nuclear induction has been studied experimentally. The apparatus used is described, both as to principle and detail. Experiments have been carried out in which the signals from protons contained in a variety of substances were observed. The results show the role played by the relaxation time, which was found to vary between about ${10}^{\ensuremath{-}5}$ second and many seconds.
1,061 citations
500 citations
TL;DR: In this article, the temperature and pressure dependence of the relative permittivity of the solvent, H2O, with respect to a modified version of the Uematsu-Franck equation was investigated.
Abstract: Within the framework of the revised HKF (H. C. Helgeson, D. H. Kirkham and G. C. Flowers, Am. J. Sci., 1981, 281, 1249) equations of state (J. C. Tanger IV and H. C. Helgeson, Am. J. Sci., 1988, 288, 19), prediction of the standard partial molal thermodynamic properties of aqueous ions and electrolytes at high pressures and temperatures requires values of the effective electrostatic radii of the ions (re), as well as provision for the temperature and pressure dependence of the relative permittivity of the solvent, H2O. Values of the relative permittivity of H2O, together with the Born functions needed to compute the standard partial molal Gibbs free energy, enthalpy, entropy, heat capacity and volume of solvation were calculated as a function of temperature and density from a modified version of the Uematsu–Franck equation (M. Uematsu and E. U. Franck, J. Phys. Chem. Ref. Data, 1980, 9, 1291). The temperature/pressure dependence of re is described in terms of a solvent function designated by g, which was evaluated in the present study at temperatures and pressures to 1000 °C and 5 kbar by regressing experimental standard partial molal heat capacities and volumes of NaCl reported in the literature together with published dissociation constants for NaClo at supercritical temperatures and pressures using the revised HKF equations of state for aqueous species. The calculated values of re decrease substantially with increasing temperature at constant pressure ⩽2 kbar, and with decreasing pressure at constant temperature 400 °C. The equations and parameters summarized below permit calculation of the standard partial molal properties of aqueous species from the revised HKF equations of state over a much more extensive range of temperature than was previously possible.
461 citations