The available data on hydrogen solubility in aluminum are reviewed. Then a mathematical analysis of the kinetics of hydrogen removal is presented. A rather complicated general equation for the hydrogen removal in batch reactors is shown to reduce to more simple expressions for certain values of anew dimensionless group, Ψ/[pct H]. This “dimensionless hydrogen concentration” can be understood to represent the ratio of the ability of hydrogen to diffuse to bubbles during their ascent divided by the capacity of the purge gas to remove hydrogen. When ψ/[pct H] ≼ 0.1, diffusion of hydrogen in the metal is rate controlling. When ψ/Ipct H] 3> 1.0, the purge gas concentration is essentially at equilibrium with the melt, and thermodynamic limitations apply. The mathematical analysis has been used, together with available data on the diffusion coefficient of hydrogen and on mass transfer coefficients, to describe the operation of industrial processes. Then a theoretical analysis of vacuum treatment is presented. The vacuum is seen to remove partially equilibrium limitations found at atmospheric pressure.

Chemical and kinetic factors related to hydrogen removal from aluminum

A new application of the time-resolved transient grating method for measuring the enthalpy and reaction volume changes in a photochemical reaction is described in detail. From the temporal profile ...

New Application of the Transient Grating Method to a Photochemical Reaction: The Enthalpy, Reaction Volume Change, and Partial Molar Volume Measurements

Super-Earths and mini-Neptunes are the most abundant types of planets among the ~3500 confirmed exoplanets, and are expected to exhibit a wide variety of atmospheric compositions. Recent transmission spectra of super-Earths and mini-Neptunes have demonstrated the possibility that exoplanets have haze/cloud layers at high altitudes in their atmospheres. However, the compositions, size distributions, and optical properties of these particles in exoplanet atmospheres are poorly understood. Here, we present the results of experimental laboratory investigations of photochemical haze formation within a range of planetary atmospheric conditions, as well as observations of the color and size of produced haze particles. We find that atmospheric temperature and metallicity strongly affect particle color and size, thus altering the particles' optical properties (e.g., absorptivity, scattering, etc.); on a larger scale, this affects the atmospheric and surface temperature of the exoplanets, and their potential habitability. Our results provide constraints on haze formation and particle properties that can serve as critical inputs for exoplanet atmosphere modeling, and guide future observations of super-Earths and mini-Neptunes with the Transiting Exoplanet Survey Satellite (TESS), the James Webb Space Telescope (JWST), and the Wide-Field Infrared Survey Telescope (WFIRST).

Laboratory Simulations of Haze Formation in the Atmospheres of super-Earths and mini-Neptunes: Particle Color and Size Distribution

Reaction volume and enthalpy changes in photochemical reaction detected by the transient grating method; photodissociation of diphenylcyclopropenone

Automated detection of methanol vapour by open path Fourier transform infrared spectrometry

Infrared absorbance measurements through a gas flow cell are made with the closed-loop circulation of vapor/air mixtures equilibrated with the use of temperature-regulated aqueous solutions. Constant reproducible vapor pressures of organic solutes are established with the equilibrated aqueous solutions. The water solvent depresses the vapor pressure of the pure organic solutes of methanol, ethanol, isopropanol, acetone, and methyl ethyl ketone (MEK). Knowledge of the solution liquid mole fractions, the pure component vapor pressures, and the Wilson coefficients permits determination of the solute vapor pressures to within 2% accuracy. Reliable aqueous solution preparation requires only the correct weighings of pure constituent materials before mixing to achieve the targeted solute liquid mole fractions. Absorbances are measured for four of the five solutes over a range of seven concentrations and for MEK over four concentrations. These concentrations show the absorbance region of adherence to Beer's law with an experimental precision of approximately ±2% for the solutes studied. Absorptivities that are calculated from the Beer's law slope are compared to the available infrared absorbance data.

Equilibrium Vapor Cell for Quantitative IR Absorbance Measurements

This study extends a model for nonideal solution behavior by considering the temperature dependence of the coefficients in the Wilson equation for the aqueous ammonia system. Twenty-seven isothermal sets of experimental PXY data up to 2 MPa (20 atm) pressure (284 points) were analyzed using an objective function based on the excess Gibbs free energy to determine the pair of Wilson coefficients for each data set. Evaluation of these results supports the interpretation of the interaction parameters in Wilson's equation as temperature-dependent entropy functions. Comparison of computed results is made with four categories of vapor–liquid equilibrium (VLE) data: (1) primary PTXY, (2) refined PTXY, (3) secondary PTXY or PTM, and (4) partial. Excellent agreement is found with computed results for all but two of these VLE data sets in the region of rapidly changing vapor composition up to 90 mole % of ammonia. A comparison is also made to the only three previously published single-temperature (isothermal) pairs of Wilson coefficients with better agreement in Y, for all three cases, and in P, for two cases. A straightforward procedure is outlined to estimate any set of PTXY values (in the range P < 2 MPa, Y < 0.9) for the aqueous ammonia system.

Aqueous Ammonia Vapor-Liquid Equilibria: Entropy and Temperature Dependence of Wilson Coefficients

Interest in the solubilities of nonreactive gases in molten salts stemmed originally from the technological need developed as a consequence of gaseous fission products of radiated molten salts. A secondary technological development associated with industrial uses of molten salts as heat treatment baths, electrolytes, and metallurgical slags led to other studies of the influence of various gases and vapors on the physical and chemical properties of the fused salts. Systematic research of gaseous solutions of molten salts has lagged behind technological studies and lies considerably more dormant than analogous studies in water and organic solvents. Theoretical studies of the liquid state and solution theory, on the other hand, have been pursued which provide applications to ionic liquid solvents such as the simpler molten salts.

Gas Solubility in Molten Salts

Mirror velocity variations in a continuous mirror drive Michelson interferometer result in erroneous interferogram sampling. The effects of both systematic and random mirror fluctuations are evaluated. Four methods of evaluation provide a means to quantify the importance of mirror velocity errors in the Fourier spectrometer's performance as a spectroradiometer. The four methods are time interval signal analysis, sine wave test, optical chopper modulation, and examination of consecutive interferograms. Examination of consecutive interferograms includes the monitoring of a constant blackbody infrared radiation source as well as an interposed ammonia sample cell for wavenumber axis registration. Each method furnishes a known input to the interferometer modulation equation (i.e. 2uv=f) and permits an internal validation of the interferometer mirror velocity evaluation results.

Mirror Velocity Sampling Errors in a Michelson Interferometer

Simultaneous measurement of gaseous diffusivity and solubility in liquids

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