The interfacial activity of 2-hydroxy-5-tert-butylbenzaldehyde oxime was studied in systems containing toluene, octane, and mixtures of these diluents containing up to 20% toluene. A significant change in the interface character of the system containing 20% toluene is observed. The interface, however, is still not fully aromatic. For a system containing 1% toluene, the interface seems to have an aliphatic character.