Vapor pressures and enthalpies of sublimation of D-glucose, D-xylose, cellobiose, and levoglucosan

The vapor pressures of alpha-D-glucose (or dextrose), D-xylose, D-cellobios e (or 4-beta-D-glucopyranosyl-D-glucopyranose), and levoglucosan (or 1,6-an hydro-beta-D-glucopyranose) have been measured using the Knudsen effusion t echnique, in the range of temperatures from 344 to 488 K. The measurements were all made in the solid sublimation regime, and enthalpies of sublimatio n mere calculated from the Clausius-Clapeyron equation. The vapor pressures may be correlated by In(P/Pa) = A - B/ (T/K), where A = 53.16, B = 23 382 (+/-600) for D-glucose (395-406 K), A = 46.29 and B = 19 006 (+/-375) for D -xylose (370-395 K), and A = 70.30 and B = 36 264 (+/-5220) for cellobiose (474-488 K). Levoglucosan displayed a solid phase transition at approximate ly 386 K, and its vapor pressure was affected accordingly. For this materia l, A = 38.96 and B = 15 049 (+/-123) in the temperature range 344-386 K and A = 31.19 and B = 12 066 (+/-709) in the temperature range 386-405 K.