Density, Enthalpy of Vaporization and Local Structure of Neat N-Alkane Liquids

The properties of alkanes are consequential for understanding many chemical processes in nature and industry. We use molecular dynamics simulations with the Amber force field GAFF2 to examine the structure of pure liquids at each respective normal boiling point, spanning the 15 n-alkanes from methane to pentadecane. The densities predicted from the simulations are found to agree well with reported experimental values, with an average deviation of 1.9%. The enthalpies of vaporization have an average absolute deviation from experiment of 10.4%. Radial distribution functions show that short alkanes have distinct local structures that are found to converge with each other with increasing chain length. This provides a unique perspective on trends in the n-alkane series and will be useful for interpreting similarities and differences in the n-alkane series as well as the breakdown of ideal solution behavior in mixtures of these molecules.

Effect of mass evaporation on measurement of liquid density of Ni-based superalloys using ground and space levitation techniques

Loss of mass due to evaporation during molten metal levitation processing significantly influences the evaluation of density, viscosity and surface tension during thermophysical property measurement. Since there is no direct way to track the evaporation rate during the process, this paper describes a mathematical approach to track mass loss and quantify any changes in alloy composition as a function of time and temperature. The Ni-based super alloy CMSX-4 Plus (SLS) was investigated and a model was developed to predict the dynamic loss of mass with time and track the potential for composition shifts throughout each thermal cycle based on the Langmuir’s equation for ideal solution behavior. Results were verified by post-test chemical analysis of key elemental constituents including Al, Cr, Ti, and Co where the error in composition for each element was less than 1% when the activity of aluminum in solution was fixed at zero – effectively eliminating evaporation of aluminum for ground-based electrostatic levitation (ESL) testing in vacuum. This model predicts the mass evaporation for Al and Co within ±6 % errors for CMSX-4 plus samples processed in ESL. Application of this technique to the space tests using the ESA ISS-EML facility shows that by conducting experiments in an inert shielding-gas environment, composition shifts due to differential relative evaporation become negligible and the composition is maintained within the desired limits. By tracking overall mass loss during testing the influence of evaporation on density measurements is discussed.

Two-Dimensional Correlation Spectroscopy (2D-COS) Studies of Solution Mixtures in the Low Frequency Raman Region

Raman spectra of a series of binary solution mixtures, including chloroform (CHCl3), ethanol (EtOH), and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), were analyzed using the two-dimensional correlation spectroscopic (2D-COS) technique in the low frequency region. Numerous asynchronous cross-peaks ubiquitously appeared in the concentration-dependent Raman spectra of these organic solvent mixtures. The result clearly demonstrated a deviation from ideal solution behavior, reflecting the presence of specific molecular interactions causing a subtle nonlinear spectral intensity response of Raman bands to the concentration changes. Furthermore, the combination of 2D-COS and low frequency Raman spectroscopy was extended to poly[(R)-3-hydroxybutyrate- co-(R)-3-hydroxyhexanoate] (PHBHx) copolymer solutions in CHCl3-HFIP co-solvents. The results suggest the existence of hydrogen bonding interaction between the PHBHx and HFIP, which is consistent with the previous infrared spectroscopic study of PHBHx solutions.

Solubility of hexachlorobenzene in organic nonelectrolyte solvents. Comparison of observed vs. predicted values based upon Mobile Order model

Experimental solubilities are reported at 25.0°C for hexachlorobenzene dissolved in 42 different organic nonelectrolyte solvents containing ether-, chloro-, hydroxy-, ester, methyl-, and tert-butyl-functional groups. Results of these measurements are used to test the applications and limitations of expressions derived from Mobile Order model. For the 33 solvents for which predictions could be made computations show that Mobile Order model does provide fairly reasonable estimates of the saturation mole fraction solubilities. Average absolute deviation between predicted and observed values is 210%. In comparison, the average absolute deviation is 2 060% when ideal solution behavior is assumed.Key words: hexachlorobenzene solubilities, organic nonelectrolyte solvents, solubility predictions.

Solubility of diphenyl sulfone in organic nonelectrolyte solvents. Comparison of observed vs. predicted values based upon Mobile Order theory

Experimental solubilities are reported at 25.0°C for diphenyl sulfone dissolved in 25 different organic nonelectrolyte solvents containing ether-, chloro-, hydroxy-, ester, methyl-, and tert-butyl-functional groups. Results of these measurements, combined with previously reported diphenyl sulfone solubilities taken from the chemical literature, are used to test the applications and limitations of expressions derived from Mobile Order theory. For the 34 solvents for which predictions could be made, computations show that mobile order theory does provide fairly reasonable estimates of the saturation mole fraction solubilities. Average absolute deviation between predicted and observed values is 49.3%. In comparison, the average absolute deviation is 5 500% when ideal solution behavior is assumed.Key words: diphenyl sulfone solubilities, organic nonelectrolyte solvents, solubility predictions.

Article

Experimental solubilities are reported at 25.0°C for phenanthrene dissolved in 41 different organic nonelectrolyte solvents containing ether, carbonyl, hydroxy, chloro, amino, ester, methyl and tert-butyl functional groups. Results of these measurements are used to test the applications and limitations of expressions derived from Mobile Order theory. For the 31 solvents for which predictions could be made, computations show that Mobile Order theory does provide fairly reasonable estimates of the saturation mole fraction solubilities. Average absolute deviation between predicted and observed values is 41.3% (excluding acetonitrile). In comparison, the average absolute deviation is 1610% when ideal solution behavior is assumed. Also reported are experimental solubilities at 26°C for pyrene dissolved in 1-hexanol, 1-heptanol, ethylbenzene, aniline, and 2-butanone.Key words: phenanthrene solubilities, organic nonelectrolyte solvents, solubility predictions.

Solubility of acenaphthene in organic nonelectrolyte solvents. Comparison of observed versus predicted values based upon Mobile Order theory

Experimental solubilities are reported at 25.0°C for acenaphthene dissolved in 36 different organic nonelectrolyte solvents containing ether-, carbonyl-, hydroxy-, ester, methyl-, and tert-butyl functional groups. Results of these measurements are used to test the applications and limitations of expressions derived from Mobile Order theory. For the 29 solvents for which predictions could be made computations show that Mobile Order theory does provide fairly reasonable estimates of the saturation mole fraction solubilities. Average absolute deviation between predicted and observed values is 37.8%. In comparison, the average absolute deviation is 1080% when ideal solution behavior is assumed.Key words: acenaphthene solubilities, organic nonelectrolyte solvents, solubility predictions.

Solubility of fluoranthene in organic nonelectrolyte solvents. Comparison of observed versus predicted values based upon Mobile Order theory

Experimental solubilities are reported at 25.0°C for fluoranthene dissolved in 36 different organic nonelectrolyte solvents containing ester, ether, hydroxy, chloro, methyl, and tert-butyl functional groups. Results of these measurements are used to test the applications and limitations of expressions derived from Mobile Order theory. For the 28 solvents for which predictions could be made, computations show that Mobile Order theory does provide fairly reasonable estimates of the saturation mole fraction solubilities. Average absolute deviation between predicted and observed values is 53%. In comparison, the average absolute deviation is 1574% when ideal solution behavior is assumed.Key words: fluoranthene solubilities, organic nonelectrolyte solvents, solubility predictions.