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
Directobservations of heterogeneous catalytic processes on a molecular level only became possible with the advent of new spectroscopic techniques and in particular, by utilizing several techniques in concert on a given catalytic process. Combining such spectroscopic investigations with concomitant kinetic investigations provides new insights into the solid state and surface mechanisms of selective olefin oxidation catalysis by mixed metal oxides. The application of multiple techniques including Raman, infrared, XRD, neutron diffraction, and XPS has provided direct evidence of several key aspects of the propylene to acrylonitrile ammoxidation mechanism over bismuth molybdate based catalysts. The mechanistic insights include: 1) direct spectroscopic evidence for solid state disproportionation of the metastable Bi2Mo2O9 phase under redox conditions, 2) identification of key catalytic phases in bismuth-iron molybdate systems, and 3) direct identification of catalytic function of active oxide ions in bismuth molybdate selective olefin oxidation catalysts.
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Continuation (Block #20)Vogel-Taman-Fulcher equation from which an ideal glass transition temperatur was derived. The viscosity dependence of T for both the Ca(NO ) and Zn(NO 3 ) solutions was found to be between that predicted by the classiaT StokesEinstein equation and that predicted using slip hydrodynamic boundary conditions. Nitrate rotation was found to be slower in Ca(N0 3 ) 2 solutions than in the corresponding Zn(N0 3 ) 2 solutions. SN 0 102? LF. 014-6601
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