Chitosan is one kind of important nature polymer.There are amino groups (—NH2) in the chitosan chains.It can be dissolved in acid aqueous solution

which lead to —NH + 3 groups formation

and displays the anionic polyelectrolyte property.The macromolecule chains are stretched caused by electrostatic repulsion of the groups —NH+3 on the chains.The stretched chains will tend to be coiled with addition of salt because of the charge screening effect of added salt.Since the determination of the intrinsic viscosity of polyelectrolyte is an effective method to study the sensibility of polyelectrolyte to the addition of salt

the dilute solution viscosity of three chitosan samples with molecular weight (Mv=2.6×105

5.6×105 and 1.06×106) was measured both in solutions of NaCl with different ionic strengths (0.01

0.03

0.06 and 0.10mol/L) and in those of NaCl

KCl

CaCl2 and BaCl2 with the same ionic strength(0.06mol/L) respectively.All the viscosity measurement is proceeded by a dilute type Ubbelohde viscometer at 308.15K.The intrinsic viscosity of chitosan is found to be a linear function of 1/I(I is the ionic strength).It is also found that the response of the intrinsic viscosity of chitosan to the added salts proceeds in the order of anion Na+>K+>Ba2+>Ca2+.Accroding to the comparison of the ionic radius and hydrate number among the four anions

it displays that the influence of intrinsic viscosity of chitosan on the added salt is due to both the anion redius and anion solvent power.Meanwhile the parameter α of Mar-Houwink equation is estimated to be 0.78

0.70

0.67 and 0.62 in corresponding added salt ionic strength(0.01

0.03

0.06 and 0.10mil/L).They are all larger than 0.5

the value common to Gaussian coils in θ-solvent.According to all hydrodynamic theories

the high α-value must indicate that the chitosan chain is very extended in aqueous of relative stiffness of Smidsrod equation

the value of empirical parameter B

which is a measure of relative stiffness of different polymer chains

is found to be 0.074.Parameter B can also be used as a measure of the sensibility of polymer to the added salt.Compared with the date of other polymers in literature

in can be concluded that the chitosan has a higher chain-stiffness and a better resistance ability to the added salt.