A high-grade filter paper impregnated with a stabilized silicone which makes it hydrophobic, retaining the normal porous character of a conventional filter paper for all non-aqueous solutions. A simple conventional filter funnel can thus be used with 1PS to separate any aqueous and immiscible organic solvent phases. Cut-off is automatic and complete just as soon as the solvent phase has passed through. The separation is extremely rapid. Whatman 1PS can be used with solvents that are lighter or heavier than water. Package of 100 sheets
