Depolarized Rayleigh light scattering studies of concentrated aqueous nitrate solutions

Carpio, Ronald A.; Mehicic, M.; Yeager, Ernest

doi:10.1063/1.441448

Cited by 8 publications

(2 citation statements)

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“…These systems are indeed structurally different, as is reflected by their difference in viscosity, acidity, propensity for supercooling, and, in the case of the nitrate systems, differences in rotational relaxation times of the nitrate ions. 22 For example, concentrated aqueous ZnCl2 solutions are strongly acidic5 as are Zn(N03)2 solutions,23 whereas Ca(N03)2-4H20 is "neutral".6 Previously, ultrasonic compressibilities of aqueous nitrates and chlorides have been reported over a much more restricted range of concentration.24,25 It was observed that at corresponding salt concentrations ds increased for salts of increasing ionic radius, and in the case of other salts the reverse was ob- served. The only conclusion that could be reached was that number of important conclusions.…”

Section: Resultsmentioning

confidence: 99%

Investigation of aqueous calcium nitrate, zinc nitrate, and zinc chloride solutions using acoustic velocity measurements

Carpio¹,

Mehicic²,

Borsay³

et al. 1982

J. Phys. Chem.

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The concentration dependence of the sound velocity at ultrasonic and hypersonic frequencies has been measured for aqueous solutions of calcium nitrate, zinc nitrate, and zinc chloride over a concentration range extending from very dilute solutions to the hydrate melt stoichiometry. Substantial velocity dispersion has been observed throughout the composition range studied for the aqueous ZnC12 system, but only at high solute concentration for the nitrate systems. Adiabatic compressibilities have been derived from the acoustic velocities and densities. A comparison of the compositional dependence of the 2-MHz adiabatic compressibilities of Ca(N0J2, Zn(NOJ2, and ZnClz solutions reveals fundamental structural differences. The magnitude of the adiabatic compressibility is shown to be a measure of the degree of complexation. Excess molar volumes and adiabatic compressibilities, derived by considering these systems to be binary mixtures of the tetrahydrate and water, are nonideal but show analogous behavior. The heat capacity ratios for several Ca(N03)2 solutions were computed from the values of the adiabatic compressibility obtained in this study and the corresponding literature values of the isothermal compressibility. IntroductionConcentrated aqueous electrolyte solutions, and particularly those having the hydrate melt stoichiometry, have in recent years assumed more interest than previously from both theoretical and technological viewpoints. The theoretical interest can largely be attributed to the ease with which a number of such systems can be supercooled over readily accessible temperature ranges; thus, these systems can be used to study the previously neglected metastable

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Section: Resultsmentioning

confidence: 99%

Investigation of aqueous calcium nitrate, zinc nitrate, and zinc chloride solutions using acoustic velocity measurements

Carpio¹,

Mehicic²,

Borsay³

et al. 1982

J. Phys. Chem.

Self Cite

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“…Although Raman spectroscopic studies have been carried out extensively on metal nitrate solutions under ambient conditions, the Raman data have been scarcely presented at high temperatures and pressures. , For example, our knowledge of the temperature dependence of the rotational dynamics below 100 °C has been developed to a considerable extent; , however, that of the rotational dynamics of ions at higher temperatures and high pressures is lacking. Hence, little has been known about ion−ion and ion−water interactions, microstructures of ion hydration, and diffusional motion of salts on the molecular level in water in the high-temperature and high-pressure region.…”

Section: Introductionmentioning

confidence: 99%

Raman Spectral Studies of Aqueous Zinc Nitrate Solution at High Temperatures and at a High Pressure of 30 MPa

1998

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We present the first direct measurement of dynamic behavior of ions in an aqueous solution at high temperatures and pressure using Raman spectroscopy. We have studied the N−O symmetric stretching mode at high temperatures up to 340 °C and at a high pressure of 30 MPa. The Raman spectra of 1.3 M aqueous zinc nitrate solution have been analyzed by curve fitting. The zinc ion forms two species. In one species Zn2+ is bound more strongly to the NO3 -, and in the other Zn2+ is bound more strongly to H2O. The ratio of the former to the latter remains unaltered with temperatures below 300 °C, but above 300 °C the ratio increases significantly. The average number of water molecules bound to Zn2+ (n H 2 O) is estimated using the intensity of peak frequency of the symmetric stretching mode of the haxaaquazinc(II) cation. As the temperature increases, the n H 2 O gradually decreases, but above 300 °C it shows a large decrease, suggesting the displacement of water molecules from the first solvation shell around Zn2+ and the concomitant entry of NO3 - into the shell. The perpendicular orientational relaxation time (τ⊥) decreases significantly with temperature; the values of τ⊥ were 1.86 and 0.25 ps, respectively, at 20 and 340 °C. The Arrhenius plot gives two activation energies, 2.1 kcal mol-1 below 300 °C and 6.4 kcal mol-1 above 300 °C. The activation energy for the orientational motion, 6.4 kcal mol-1, is larger than that for orientational motion of water, 4−5 kcal mol-1, and we assume that orientational motion of the anion above 300 °C requires the breaking of water−water hydrogen bonds. Furthermore, the experimental values of the perpendicular diffusion constant (D ⊥) at higher temperatures than 300 °C are in agreement with those of D i calculated from the slightly damped free-rotor (SDFR) model, and the rotation around the C 3 axis of the anion is confirmed to proceed rapidly and approach that in the free dilute gas phase.

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Aqueous solutions of sodium methylsulfate by Raman scattering, NMR, ultrasound, and density measurements

Koda

Nomura

1985

J Solution Chem

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Depolarized Rayleigh light scattering studies of concentrated aqueous nitrate solutions

Cited by 8 publications

References 41 publications

Investigation of aqueous calcium nitrate, zinc nitrate, and zinc chloride solutions using acoustic velocity measurements

Investigation of aqueous calcium nitrate, zinc nitrate, and zinc chloride solutions using acoustic velocity measurements

Raman Spectral Studies of Aqueous Zinc Nitrate Solution at High Temperatures and at a High Pressure of 30 MPa

Aqueous solutions of sodium methylsulfate by Raman scattering, NMR, ultrasound, and density measurements

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