Some Physicochemical Properties of Specific Polysaccharides*

In recent years the study of immunologically specific polysaccharides has not only contributed to the understanding of bacterial specificity (1) but has also proved of purely chemical interest because of the unusual structure of certain members of the group. Thus the specific polysaccharide of Type III pneumococcus has been shown to be a polyaldobionic acid built up of glycurono-glucose units (2, 3). It is, moreover, a typical colloid in the sense that it does not diffuse through collodion or parchment into water, and is, by virtue of its structure, so strong an acid that its aqueous solutions turn Congo red paper blue. Hence it seemed of interest to study some of the physicochemical properties of solutions of its salts, the more so as little is known of the behavior to be expected of an organic, colloidal, strong electrolyte devoid of basic groups. Accordingly, the sodium salt of the Type III pneumococcus specific polysaccharide was subjected to a study of its viscosity, conductance, and its behavior on diffusion. Measurements were also made on solutions of other specific polysaccharides. The diffusion data are reserved for a forthcoming paper dealing with the molecular weight of specific polysaccharides, in which connection the data recorded in the present communication will again be taken up. Physicochemical studies have previously been made of gum arabic, a carbohydrate of a character somewhat analogous to that of the Type III pneumococcus polysaccharide. This substance, however, is the salt of a much weaker acid than the Type III