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 93: 10 µm
This filter paper is intermediate in speed and retention between Grades 1 and 4. Available in a dispenser pack, which 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.
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 qualitative range. This filter is also available in the FilterCup, a convenient, disposable 70 mm filter funnel with a 250 ml capacity, molded from polypropylene with an integral, heat bonded filter. Also available as Grade 113V.
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. Also available prepleated as Grade 114V.
Fast filter paper. Stated in a number of standards and methods, e.g., Aflatoxin determination in animal feed (BS 5766-7) and Mercury determination in sludge (EPA method 105). Also available prepleated as Grade 588 ½.
Grade 1573: 12-25 µm
A fast filter paper with high wet strength. It has a very smooth surface making it easy to scrape or wash off precipitate. Resistant against: sulfuric and nitric acid solutions (up to 40% at 50°C), hydrochloric (up to 10% at 100°C, 20% at 60°C, 25% at 20°C) and alkalis (up to 10% at 20°C). Also available prepleated as Grade 1573 ½.
Grade 1575: < 2 µm
Slow filter paper with high wet strength. This paper has the same chemical resistance characteristics as Grade 1573 (see under Grade 1573 above).
See filter papers for technical use section, for additional wet strengthened filter papers.