Abstract: The polysaccharide of pleuratu ostreatus was fractionated by repeated precipitation method. Modified Elias cloud-point titration method with an UV detecter was used to determine the cloud-point. It was found that water/acetone (83.5:16.5 by volume) is a θ-solvent for the polymer at 25 ℃. Number average molecular weights of all samples fractionated were characterized by rapid dynamic membrane osmometry and viscometry. The second virial coefficient A_2 decreases as the molecular weight in-creases. The relationship is A_2=2 slope (M_nRT)~(-1/2).
The intrinsic viscosities were determined by capillary viscometry in θ-solvent. Thus and thus a mondispersed [η]～M relationship has been obtained:
[η]_θ=0.124~(0.513)
The unperturbed dimension ...

Key words: Pleuratu ostreatus, Polysaccharide, Dilute solution, Molecular weight, Cloud-point titration