Isolation of Lignin from Finely Divided Wood with Neutral Solvents

Abstract

IN 1939, Brauns¹ found that a few per cent of the total amount of lignin is present in the extractives obtained from black spruce with ethanol. It is now well known that greater proportions of lignin cannot be extracted from wood unless the solvent contains an acid reagent or rather drastic conditions are used, resulting in more or less severe alteration of the lignin. This fact is usually explained in two ways: (1) chemical bonds exist between lignin and the carbohydrates; (2) lignin has a very high molecular weight, and may form a three-dimensional network. A third possibility, that weak forces like hydrogen bonding and physical phenomena may be involved in the retention of lignin, has not been given much consideration, though such forces would render the dissolution of cellulose in water impossible.