Physico‐chemical studies on indian plant gums. Polyelectrolytic behaviour of acacia catechuic acid

The conductivity, viscosity and p H of Acacia catechuic acid (ACA), an acid obtained from the electrodialysis of gum Acacia catechu have been investigated under different experimental conditions. It is noted that there is a sharp rise in the reduced viscosity η sp /C as the concentration of ACA is reduced. The viscosity of ACA follows the expression the value of A = 0.4237 and B = 1.84. The reduced viscosity of ACA has been investigated with dilution in isoionic concentrations of H 2 SO 4 . It has been found that by the addition of 2.0·10 −4 g. equiv./ l. , the sharp rise in η sp /C versus C vanishes, the curve showing a well defined maxima. With increasing concentrations of H 2 SO 4 the maxima shifts towards higher values of ACA concentration, and at 1.0·10 −3 g. equiv./ l. of H 2 SO 4 , the η sp /C versus C curve is a straight line. The λ (equiv. cond.) versus √C curve (Phoreogram) is much steeper than for a comparable simple electrolyte. The phoreogram is strongly concave upward. It is shown that the conductivity is largely due to the hydrogen counterions. A number of equations have been found to represent the equivalent conductance of ACA with dilution. The degree of dissociation has been determined from measurements of electrical conductivity and of p H XS. A discrepancy in the results has been tentatively explained. The degree of dissociation decreases with increasing concentration of ACA. It is noted that the conductance of ACA/electrolyte mixtures is 5 to 12% higher than the calculated value. A number of equations have been shown to represent the concentration dependence of p H for ACA.