AbstractReduced chicken feather keratin forms a soluble complex in neutral aqueous sodium alkylbenzenesulfonate (average: dodecylbenzenesulfonate). The chemical composition, specific refractive increment, partial specific volume, electrophoretic mobility, osmotic pressure, diffusion constants, and ultracentrifugal sedimentation of the complex have been studied. The complex is heterogeneous but similar to egg albumin–sodium alkylbenzenesulfonate mixtures previously studied in general properties, including fiber‐forming properties, the average molecular weight of the dispersed protein units, and the relative symmetry of the dispersed units in dilute solut