An examination of the effects produced by ferric oxide pigments on the drying rates of linseed oil films. Solidification curves obtained at room temperature indicated a faster drying rate with increasing pigment concentration. The different types of ferric oxide studied exerted different catalytic activities which depended on the proportion of ferric oxide in the pigment, the specific surface area of the pigment particles, and the organic solubility of the pigment. Both homogeneous and heterogeneous catalysis are though to play a part in the reactions taking place. Tables, graphs, references.