Spherical shaped reaction vessel constructed with a flange having a groove formed in the sealing surface of the flange. Flange is also ground to permit a greased seal with any of the lids CG-1940 through CG-1946. Vessel will fit standard heating mantles CG-10000 through CG-12502. For clamp see CG-141 or CG-141-T. For o-ring see CG-147.