These extremely strong filter papers have a high wet strength due to the addition of a small quantity of chemically stable resin. Their use in 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 (fluted) forms.
Qualitative filter papers, Grade 91
Wet strengthened grades 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.

Whatman grade 91 dia        110mm 11 cm      pack of 4000 pc      Cat no 1091-110

Whatman grade 91 dia        125mm 12.5cm    pack of 4000 pc      Cat no 1091-125

Whatman grade 91 dia        150mm 15 cm      pack of 1000 pc      Cat no 1091-150

Whatman grade 91 dia        165mm 16.5cm   pack of 1000 pc       Cat no 1091-165

Whatman grade 91 dia        185mm 18.5cm    pack of 1000 pc      Cat no 1091-185

Whatman grade 91 dia        190mm 19 cm      pack of 1000 pc      Cat no 1091-190

Whatman grade 91 dia        240mm 24 cm      pack of 1000 pc      Cat no 1091-240