The formation of precipitates by solutions of tannins and alkaloids at pH 5.4, 20°C was examined. Used tannins were tannic acid JP, geraniin, punicalin and chebulinic acid, and alkaloids were berberine, cinchonine, strychnine, papaverine, quinine, nicotine, atropine, caffeine and theobromine. The concentration of tannins was 0-3.0%, and that of alkaloids was 0-0.05%. The experiments with tannic acid JP and 0.01% solutions of berberine, cinchonine, papaverine, quinine and strychnine showed that the precipitate which once increased with an increase in tannin concentration, stopped increasing or quikly decreased when the concentration of tannin increased over 1.5%. Geraniin and chebulinic acid showed similar behavior. However, the experiments with punicalin and the three alkaloids showed an almost linear increase of the precipitates due to the increase of tannin concentration. The experiments with various concentrations of caffeine, nicotine, theobromine and tannic acid JP showed that the amounts of precipitates which once increased with an increase in tannin, quickly decreased upon the further increase of the tannin concentration, and finally no precipitate or almost no precipitate occurred when the concentration of tannin reached 3.0%. A marked increase of the molar ratio of tannin to berberine in the precipitate formed by tannic acid JP and berberine was observed upon the increase of the concentration of tannic acid JP. The increase of this ratio over 2 accounts for the solubilization of precipitates. The paper elecrophoresis of precipitates and solutions showed differences of the extent of dissociation of complexes due to differences of the ratio of alkaloids to tannic acid JP.
