This work presents experimental investigations of the explosion behaviour of diethylketone and methanol with pure oxygen and oxygen/nitrogen mixtures. The experimental setup consists of a tube with a length of 2000 mm, an inner diameter of 50 mm and an observation unit. Besides pressure recordings, characteristics for heterogeneous detonations and deflagrations were observed by high-speed photography. Different regimes of the explosion behaviour were determined as a function of the initial pressure and of the content of oxygen in the gas phase. Furthermore, the experiments showed that the formation of droplets is a necessary condition for the formation of detonations near the surface of organic liquids.