PHYSICOCHEMICAL STUDIES OF LIGNINSULPHONATES: III. PROPERTIES OF FRACTIONS PREPARED BY SUCCESSIVE SULPHONATION OF PERIODATE LIGNIN

Abstract

Periodate lignin was sulphonated in stages by a series of short bisulphite cooks. At each stage the soluble ligninsulphonate was removed and purified, and the residue was resulphonated. The 14 fractions thus obtained had constant methoxyl content and ultraviolet absorption coefficients. There was a gradual increase in the sulphur content as the integral reaction time increased, but 26% of the ligninsulphonate possessed a sulphur content of less than 3%. There was a marked increase in both the intrinsic viscosity and rate of solution with increase in reaction time. The mechanism of the sulphonation reaction is discussed in the light of these results.