title: Oiling out or molten hydrate-liquid-liquid phase separation in the system vanillin-water.
abstract: Vanillin crystals in a saturated aqueous solution disappear and a second liquid phase emerges when the temperature is raised above 51 degrees C. The phenomenon has been investigated with crystallization and equilibration experiments, using DSC, TGA, XRD and hot-stage microscopy for analysis. The new liquid solidifies on cooling, appears to melt at 51 degrees C, and has a composition corresponding to a dihydrate. However, no solid hydrate can be detected by XRD, and it is shown that the true explanation is that a liquid-liquid phase separation occurs above 51 degrees C where the vanillin-rich phase has a composition close to a dihydrate. To our knowledge, liquid-liquid phase separation has not previously been reported for the system vanillin-water, even though thousands of tonnes of vanillin are produced globally every year.
authors.affiliation: Department of Chemical Engineering and Technology, Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
authors.forename: Michael
authors.initials: M
authors.lastname: Svärd
authors.forename: Sandra
authors.initials: S
authors.lastname: Gracin
authors.forename: Ake C
authors.initials: AC
authors.lastname: Rasmuson
mesh_terms: D019840:2-Propanol / Q000737:chemistry; D001547:Benzaldehydes / Q000032:analysis*; D002152:Calorimetry, Differential Scanning; D002626:Chemistry, Pharmaceutical; D003460:Crystallization; D004339:Drug Compounding; D004355:Drug Stability; D012997:Solvents; D013696:Temperature; D013816:Thermodynamics; D013818:Thermogravimetry; D014867:Water / Q000032:analysis; D014961:X-Ray Diffraction
chemical_list: D001547:Benzaldehydes; D012997:Solvents; D014867:Water; C100058:vanillin; D019840:2-Propanol