Lignin Distribution in Soda-Oxygen and Kraft Fibers as Determined by Conventional Electron Microscopy

The lignin distribution in loblolly pine ( Pinus taeda L.) fibers produced by soda-oxygen and kraft pulping was investigated by electron microscopy of KMnO 4 stained ultrathin sections and direct carbon replicas. A more extensive delignification of outer layers of fibers was found in soda-oxygen pulps than in kraft pulps. However, kraft pulping is more effective than soda-oxygen pulping in removing lignin from the lumen side of fibers. These observations were in good agreement with an earlier study of the lignin distribution within pulp fibers performed with SEM-EDXA technique.