These Pyrex® cylindrical separatory funnels are for the addition of material to a reactive mixture in a closed system where air must be excluded. The dropping tube below the stopcock permits delivery of solutions by drops. The lower end of the dropping tube extends below the lower end of the inner 24/40 ST joint. The funnels have a micro-finish PS PTFE plug which fits into the micro-finish glass barrel. The plug also reduces freezing problems and grease contamination. The funnels also have strong, hollow ST glass stoppers. For replacement glass stoppers, see Cat.No. 1-7650; for replacement PTFE stopcock plugs, see Cat.No. 1-7681.