Whatman 1PS Phase Separator Paper is a hydrophobic filter for routine solvent extraction. Within seconds it retains aqueous phases, while solvent phases flow through. 1PS Phase Separator is impregnated with stabilized silicone, creating a hydrophobic filter paper that can replace separatory funnel use in certain applications. The solvent phase flows through the paper quickly and cleanly, automatically stopping after the process is complete; all of the aqueous phase is retained. No special training required. 100 circles/box.