Abstract
Ion-exchange reactions between cations, K, Ca and Mg, bound to pectin and Na of NaCl added to pectin solutions were investigated in detail. Pectic substance, extracted from radish root by treating with hot 2% Sodium hexametaphosphate solution in pH 3.7, was acidified with HCl and dialyzed to prepare pectinic acid containing minor cations. Then, pectinic acid was converted to pectinates containing K, Ca and Mg independently or some of these cations by treating with the individual salts or the mixture of the salts, following dialysis to eliminate the excess salts. The formation of the salt of COOH residues in pectin with such cations was recognized by the IR spectral absorption method before and after the treatment. The cation content in the pectinates was determined by atomic absorption spectrometry. And the changes of cation content in the pectinates after treating with NaCl solutions in different concentration, followed by dialysis, were measured. The experimental results indicated that the initial cation content in the pectinate decreased in inverse proportion to the increase of Na content in it according to the increment of NaCl added, showing greater effect of Na to exchaging the cations in order of K>Mg>Ca in the pectinate.
