SEPARATION OF WOOD HEMICELLULOSES

Some of the factors influencing the separation of xylan and galacto-glucommanan-type hemicelluloses are discussed. The importance of treating the crude hemicellulose mixture with buffered sodium chlorite at room temperature to remove all lignin is demonstrated. Only part of the galactoglucomannan is directly precipitated by the addition of barium hydroxide, but a further quantity is removed by careful titration with ethanol to a flocculation point. The supernatant then yields a highly enriched xylan. Results are reported for ponderosa pine and Douglas fir.