Flat flange reaction vial with groove in the flat flange and round base. Flat flange reaction vials are large-volume reaction vials that can be used as an alternative to standard round bottom flasks. The flat flange reaction vial is closed with a separately available lid. 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. The thick-walled construction and geometry make these vessels suitable for safe working under pressure and vacuum.