Lignin analysis by permanganate oxidation. II. Lignins in acidic organosolv pulps

The permanganate oxidation method was used to analyze residual lignins in N orway spruce (Picea abies) organosolv pulps. The pulps were produced by eth anol water solvolysis catalyzed by 0.005M or 0.01M H2SO4 at 175 degrees C. Condensation reactions of residual lignin occurred at a significant rate wh en the ethanol volume fraction was 0 % but not when it was greater than or equal to 51 %. There was selective removal of uncondensed guaiacyl units wh en mixtures of 51 %, 76 %, and 91 % ethanol were used. The condensed units in the native lignin were less reactive and accumulated in the fibers. They constituted > 60 % of the C-9 units by the time 80 % delignification was a chieved. A limited amount of results are presented for a kraft pulp with ho pes of enhancing the credibility of permanganate oxidation as an analytical tool for residual lignins.