Whatman No. 5

Of all Qualitative Grades, this filter paper has the best retention. Fine crystalline precipitates (less than 2.5 µm) are retained. ASTM initial filtration speed is 250 seconds. Extensively used in water analysis. Smooth surface is normally hard. 0.6 mg ash content per 12.5 cm circle. (For cost savings, see Ahlstrom equivalent, 447-000-02 Series)