Whatman Type 1PS. A high grade filter paper impregnated with a stabilized silicone which renders it hydrophobic while retaining the normal porous character of conventional filter paper for all non-aqueous solutions. It will separate aqueous solutions from water immiscible solvents, either heavier or lighter than water. Phase cut-off is automatic and complete just as soon as the solvent phase has passed through. 100 circles/box.