| Popis: |
A comparison of the interaction of a commercially available xylan, a d -galactose-deficient galactoglucomannan from Englemann spruce holocellulose, a highly branched “amyloid” from tamarind seed, and a commercial amylose preparation from potato starch, in concentrated aqueous calcium chloride solution showed that all four of these polymers reacted with iodine-potassium iodide solution to give a blue product that was soluble at low concentrations of reagents. In agreement with data in the literature, other highly branched polysaccharides such as cherry gum and d -galactose-rich galactoglucomannans did not reach with iodine under these conditions. Qualitative tests showed that iodine and calcium ion, as well as polysaccharide, were present in the isolated complexes, and spectrophotometric measurements showed the dependence of complex formation on the concentration of iodine and polysaccharide as well as on the time and temperature of reaction. Although the polysaccharides reacted to give a dark blue, starch-like coloration with iodine, potentiometric titration showed that only the xylan was complexed with iodine in a manner similar to that of amylose, while galactoglucomannan and “amyloid” bound iodine in a looser fashion typical of poly(vinyl alcohol)-iodine complexes. The iodine content of the complexes from xylan, “amyloid”, and galactoglucomannan, unlike the iodine content of the amylose complex, was found to vary with the concentration of the reactants, indicating the absence of a preferred stoichiometry. |
