The Electrophoretic Behavior of Lignin.

The precipitation of lignin from aqueous solutions of sodium or potassium hydroxide is rather easily brought about by lowering the pH to from 3_to 4, but is not effected by the addition of organic dehydrating agents. The observation that under definite conditions a gel can be formed has led to a consideration of its electrophoretic behavior. At the pH levels at which lignin is soluble, the charge on the complex is probably due to the dissociation of phenolic hydroxyl groups together with enolizable carbonyl groups. At the pH of most soils, however, conditions are not only unfavorable for the ionization of the phenolic hydroxyls but often cause the precipitation of isolated lignin. It is over this pH range, however, that lignin undergoes various reactions, ultimately forming humus. Schubert et al (1) have investigated the electrophoretic activity of soluble native and of enzymatically liberated lignins over the pH range of approximately 9.5 to 11. Both lignins increased in mobility as the pH increased, with considerable mobility at the zone of initial precipitation. The electrophoretic pattern for oak lignin indicated a homogeneous compound, and the pattern for white Scots pine indicated a heterogeneous compound. The purpose of this investigation is to determine the electrophoretic behavior of lignin and modified lignins over the pH range of about 2 to 6.