These extremely strong filter papers have a high wet strength due to the addition of a small quantity of chemically stable resin. Normal qualitative applications will not introduce any significant impurities into the filtrate. The resins do, however, contain nitrogen so these grades should not be used in Kjeldahl estimations, etc. Some wet-strengthened grades are available in folded (prepleated) forms.
Grade 91: 10 µm
A general-purpose creped filter for less critical routine analysis. Widely used to assay sucrose in cane sugar and within pharmaceutical laboratories for routine filtration.
Grade 113: 30 µm
Ultra high loading capacity with a particle retention making it ideal for use with coarse or gelatinous precipitates. Fastest flow rate of the qualitative grades. Creped surface. Thickest filter paper in the Whatman® range. This filter is also available
in the Whatman® Filter Cup. This is a convenient, disposable 70 mm filter funnel with a 250 mL capacity, molded from polypropylene with an integral, heat bonded filter.
Grade 114: 25 µm
Only half the thickness of Grade 113 and suitable for coarse or gelatinous precipitates. Smooth surface for easy recovery of precipitates.
Grade 520 bII: 15-19 µm
A thick paper with high wet strength offering a very high flow rate. Also available prepleated as 520 bII 1¼2.
Grade 2294: 8-15 µm
A very thick filter card with high wet strength. Offers very high flow rate and retains medium to coarse particles.
Grade 2589 a: 6-12 µm
A fast to medium fast filter with high wet strength offering medium retention.
Student Grade/Grade 93
Designed for educational use, this filter paper is intermediate in speed and retention between Grades 1 and 4. Student grade retains those flocculent and medium precipitates most often encountered in student experiments.
Available in a dispenser pack, it can be attached to the wall or bench, placed on a shelf either upright or flat, and used
as a normal carton or as a convenient dispenser. The envelopes are released individually for easy one-at-a-time removal. Package and envelopes are clearly marked for size and content.