Vacuum. Desiccant tube has two-way action that permits the use of a smaller desiccant volume and better air contact with desiccant. During the final stage of drying, the T-bore stopcock is turned so that the evacuation path is directly over the desiccant, while in the early stages the desiccant is bypassed. The upper 24/40 joint is offset, condensed liquid does not drop over the inner tube. Opening to the inside cahmber is 40/35. Complete consists of condenser, drying chamber, desiccant tube with stopcock and round bottom boiling flask.