The Molecular Properties of Ghatti Gum: A Naturally Occurring Polyelectrolyte

Abstract

Abstract An authenticated sample of ghatti gum from Anogeissus latifolia has been fractionated by ethanolic precipitation (Fraction I), and chromatography on silica gel (Fractions 2 and 3). The equivalent weights found were 1,750, 1,800 and 2,040 respectively. The sodium salts of the fractions have been studied in various salt solutions by viscosity and light scattering methods. From the latter the molecular weights (= 2·1, 2·7, and 2·6 ± 106 respectively), radii of gyration, and some idea of molecular shape have been obtained. The molecule appears to be rod shaped. The expansion factors of the molecules calculated from the light scattering and the viscosity data agree with each other. Reasons for the difference in the values of the calculated and observed second virial coefficients are discussed.