Heavy wall reaction flask with jacket, part of the one-piece pressure reactor, for use at elevated pressures. With vertical Screw thread necks for positive connection of stirrer, funnel, thermowell, condenser, etc. Cooling/heating jacket is heat sealed. Inlet/outlet on jacket has easy connect/ disconnect size 28/15 O-Ring ball joints. Bottom outlet is a 28/15 O-Ring ball joint with size –116 FETFE O-Ring, and a threaded valve for retrieving contents of flask.