Differential Thermal Analysis of α-Lactose Hydrate

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Differential thermal analysis was the technique in studying thermal characteristics of α-lactose hydrate. α-Lactose hydrate exhibited an endotherm corresponding to the elimination of the water of crystallization, followed by a small exotherm, and then by a melting endotherm. The process of dehydration of α-lactose hydrate by methanol and heating was recorded clearly on the thermograms as the successive changing into the stable and unstable anhydrous form, α-Unstable anhydride was characterized by the endo- and exothermic peaks at 183 and 190C. These peaks remained after the conversion of the anhydrous form to the crystalline α-hydrate on exposure to moistened air, though no difference in the forms was observed on infrared spectra and X-ray diffraction patterns. α-Lactose hydrate in dried skim milk and dried whey was detectable on the thermogram based on the development of the water endotherm. Differential thermal analysis is a promising and useful technique for the characterization of lactose.