title: Composition dependence and the nature of endothermic freezing and exothermic melting.
abstract: The heat capacity, C(p), and enthalpy and entropy change of alpha-cyclodextrin, H(2)O, and 4-methylpyridine solutions have been studied during their freezing on heating, isothermal freezing, and the solid's melting on cooling. Freezing occurs in several endothermic steps on heating to 383 K and alpha-cyclodextrin rich solutions freeze in four steps. The melting rate becomes slower with decrease in temperature and its steps merge. Decreasing the amount of alpha-cyclodextrin decreases the C(p) change on freezing. The endothermic freezing phenomenon differs from freezing of a pure liquid and is attributed to formation of a solid inclusion compound and its incongruent way of exothermic melting.
authors.affiliation: Istituto per i Processi Chimico-Fisici del CNR, via G. Moruzzi 1, 56124 Pisa, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Ferrari
authors.forename: E
authors.initials: E
authors.lastname: Tombari
authors.forename: G
authors.initials: G
authors.lastname: Salvetti
authors.forename: G P
authors.initials: GP
authors.lastname: Johari