Light-scattering Studies in Solutions of Gum Arabic

Light-scattering measurements of gum arabic have been made in aqueous solution, in 0.02 N-KCI solution, and in a mixture of 0.02 N each of K+, Ca2+, and Mg2+chloride solution. The molecular weight of the gum after proper correction records a value of 0.58 X 106. The molecular size, i.e., the root-mean-square end-to-end dis­tance of the polymeric coil is 240 mμ in aqueous solution. This is reduced to 109mμ. in 0.02N-KCl and 113 mμ in a mixture of 0.02 N-KC1, CaCl2, and MgCl2 solutions. These results indicate that a high contraction of the gum molecule takes place in presence of gegen ions.