AbstractHigh resolution electron microscopy of sodium lignin sulfonates revealed a granular microstructure of spherical particles of diameters ranging from 30 to 90 A. The weight average particle weight,Pwwas computed from the dimensions measured on the electron micrographs and the density of lignin. For a fraction of intermediate molecular weight, the particle diameter derived fromPwwas 64 A., in fair agreement with a value of 49 A. computed from the sedimentation equilibrium molecular weight. A high molecular weight fraction contained, in addition to the granular moiety, larger structures which appeared to be aggregates of the granules. The particle weight distribution for the high molecular weight fraction was similar to the distribution of sedimentation constants previously found for alkali lignins. The spherical shapes for both the granules and the aggregates was in accord with the compact spherical configuration previously proposed for lignin sulfonates in aqueous solution.
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