Reaction vessel, cylindrical, graduated with groove in the flat flange. The flat flange reaction vessel is closed with a lid which is available separately. Both parts are held together by a clamping ring. A sealing ring, or the use of grinding grease, prevents the grinding surfaces from jamming. Suitable silicone and FEP sealing rings are available separately. The flat flange vessel can be combined with other components (e.g. coolers, stirrer shafts and dropping funnels) by means of various standard ground joints in the lid.Areas of application: preparatory work, such as general reactions, distillation, evaporation and drying, in which solid or viscous substances are produced.