Abstract
The main physicochemical properties of the polysaccharide called Xanthan produced by Xanthomonas compestris are discussed: the activity coefficient of the counter‐ion, the pK(α), and the ionic selectivity are investigated and compared to those of a carboxymetholcellulose. The weight‐average molecular weight (Mw = 2 × 106), the intrinsic viscosity and the constant of sedimentation are determined as a function of the ionic strength. It is proved that in dilute solution, there is no intermolecular association, whatever the ionic strength. The conformation is proposed to be a rigid rodlike molecule whose length is 6000 Å, independent of ionic strength > 10−2N.

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