PHASE-EQUILIBRIA OF NARROWLY DISTRIBUTED DEXTRANES IN THE TERNARY-SYSTEM DEXTRANE WATER-ETHANOL

In this work we consider the phase equilibria of narrowly distributed dextranes with different average molecular masses in the ternary syste m dextrane-water-ethanol which are of interest in the fractionation of broadly distributed dextranes. It can be emphasized that the degree o f polymerization of the dextrane has a great influence on the phase eq uilibrium in this ternary system. Numerical calculations were performe d using the model of Flory and Huggins. The agreement between experime ntal and theoretical phase equilibria is very good. The interaction pa rameter of the Flory-Huggins model for the water-dextrane interaction is independent of the molecular mass of the dextrane. The interaction parameters for the water-ethanol and ethanol-dextrane interactions sho w a dependency on the molecular mass of the dextrane. However, both in teraction parameters reach a limiting value for high molecular mass de xtrane.