THE EFFECT OF SOLVENT AND TEMPERATURE ON THE VISCOSITY OF THE POLYSACCHARIDE OF IRISH MOSS AND THE EFFECT OF SOLVENT ON ITS INITIAL GELATION

Abstract

The viscosity of aqueous extracts of Irish moss (Chondrus crispus) has been found to depend mainly on the concentration of the neutral salts present in the solution. Samples of dialyzed polysaccharide, however, show considerable variation. The relation between the specific viscosity and the concentration in dilute aqueous solutions and formamide is such that η_sp = ac_v + bc_c², where η_sp is the specific viscosity, c_v the concentration, and both a and b are constants. In aqueous solution these constants are decreased by the addition of neutral salts. A rise in temperature causes a decrease in viscosity. This decrease is less rapid for solutions in formamide and aqueous solutions containing neutral salts. The effectiveness of individual salt solutions in promoting a decrease in viscosity coincides with their effect in producing precipitation of the polysaccharide. The order of decreasing effectiveness was: potassium chloride, calcium chloride, sodium chloride. When the concentration of gelose is such that gelation takes place on standing, measurements of viscosity become irregular and are not reproducible. The concentration of gelose at which the regular viscosity measurements are obtained decreases with increasing concentration of neutral salts. The rigidity of the gels so formed also decreases. The firmness of a gel seemingly depends on the concentration and type of neutral salt, as well as on the intrinsic viscosity of the polysaccharide. The intrinsic viscosity is defined as: the limit of the specific viscosity as the concentration approaches zero.