Interpretation of the global heat of melting in eutectic binary systems

Abstract

Highlights-Ten eutectic binary phase diagrams are exploited with new thermodynamic approach.-Heats of melting of binary mixtures are considered from solid state up to melting.-Linear relationship is found between heat of melting and mole fraction.-Extrapolated values at x = 0 and x = 1 are interpreted as melting enthalpies.-A mathematical model is proposed to explain the experimental data.

Polymorphism and thermophysical properties of l- and dl-menthol

“…The heat capacities of liquid and α-crystalline L-menthol from Corvis and Espeau [6] are in a remarkably good agreement with our results (within 3 %) when considering that a heatflux DSC was employed. It should be noted that the authors of [6] used a three-run procedure, repeated the experiments several times with different samples and obtained deviations from reference data for testing compounds (water and naphthalene) up to 10 %. By comparing with the reference data, a steeper slope of temperature dependence of heat capacity data reported in [6] can be seen.…”

“…The authors claimed a somewhat optimistic expanded uncertainty (0.95 level of confidence) for L-menthol (1.2 % to 3.2 %, which most likely reflects only a statistical component of uncertainty, i.e., type A uncertainty) when compared to the uncertainties of their measurements with the reference materials. Corvis and Espeau [6] also reported heat capacities of the β for of L-menthol between 204 K and 226 K, which are 11 % to 16 % lower than our adiabatic calorimetry results for the α polymorph of L-menthol. A lower heat capacity for the metastable phase is in agreement with our results on DL-menthol, but such a large difference between the two polymorphs is unlikely.…”

“…It should be noted that the authors of [6] used a three-run procedure, repeated the experiments several times with different samples and obtained deviations from reference data for testing compounds (water and naphthalene) up to 10 %. By comparing with the reference data, a steeper slope of temperature dependence of heat capacity data reported in [6] can be seen. The authors claimed a somewhat optimistic expanded uncertainty (0.95 level of confidence) for L-menthol (1.2 % to 3.2 %, which most likely reflects only a statistical component of uncertainty, i.e., type A uncertainty) when compared to the uncertainties of their measurements with the reference materials.…”

“…In any of the production methods, isolation from multi-component systems via distillation, extraction, or crystallization is a necessary step. The recent increase of interest in the description of solid-liquid equilibria (SLE) [2][3][4][5][6] and liquid-liquid equilibria (LLE) [7] of menthol-based mixtures is likely related to an attempt to improve the process efficiency.…”

“…Temperatures and enthalpies of fusion of some polymorphs of L-and DLmenthol were reported several times, but a solid review and comparison of the previous values is needed. Heat capacities of the condensed phases for L-menthol were recently determined [6] by differential scanning calorimetry (DSC) which typically provides heat capacity data with much higher uncertainty than adiabatic or Tian-Calvet calorimetry. Vapor pressure measurements of menthols were performed in [14][15][16][17].…”