Heat capacities and concentration fluctuations in mixtures of 1,2-dibromoethane with alkanes

Abstract

Excess volumes, excess heat capacities and light scattering have been measured for several 1,2-dibromoethane-alkane (n-heptane, n-octane, n-tetradecane, cyclooctane and 2,2,4-trimethylpentane) systems. The results show that there is good agreement between values of the concentration-concentration correlation function S , ,, as calculated from light-scattering data, and the predictions of the simple rigid lattice model of Flory and Huggins, which estimates the relative effects of the differences in molecular sizes and of differences in the interaction energies of the two components. The results also confirm the utility of S,, as predictor of the existence of W-shaped excess isobaric heat capacity (CE) curves, although other effects, such as the destruction of the (partial) correlation of molecular orientation may complicate this issue.

Concentration fluctuations and surface adsorption in non-ideal binary mixtures. A light-scattering and surface tension study

“…A more familiar way of pointing out the non-ideality of mixtures is to show the excess Gibbs energy G E curves. We have calculated them by integration of the osmotic susceptibility results (see the Appendix), 17 and the results are shown in Fig. 2.…”

“…13 The depolarisation ratios were calculated from the ratio of the intensities of the light scattered at 35 and at 145 . The method for obtaining the osmotic compressibility from the raw data has been described in detail in a previous work, 17 and it is summarized in the Appendix. The precision of the osmotic compressibility is estimated to be better than 6%.…”

CHAPTER 7. Excess Volumes of Liquid Nonelectrolyte Mixtures

“…58,[279][280][281] It is based on interesting questions associated with the existence of rotamers in the a,o-dihaloalkanes showing large differences in the corresponding dipole moments (and differences in the corresponding molecular volumes), and on interesting questions concerning proximity effects. Recently, Chorążewski et al 282 presented experimental densities, heat capacities at constant pressure (Micro DSC III, from Setaram) and speeds of ultrasound at 4 MHz (pulse-echooverlap apparatus) for mixtures of 1,6-dichlorohexane (DCH) with n-heptane at 293.15 K, 298.15 K, 303.15 K, 308.15 K and 313.15 K, covering the whole composition range.…”

Heat Capacity, Speed of Ultrasound, and Density for 1,5-Dibromopentane + Heptane within the Temperature Range from 293.15 K to 313.15 K

“…[2][3][4][5][6][7][8] It is most interesting that, for the investigated mixtures of 1,5-dibromopentane with heptane, the excess heat capacity as a function of mole fraction x is W-shaped like for mixtures of alkanes with R,ω-dichloroalkanes [11][12][13]17,18 and 1,2-dibromoethane. 25 Grolier and Wilhelm et al 9 have discovered the W-shape anomaly of the dependence of C p E on composition. Since then, the interest in this phenomenon is constantly growing.…”