Whatman No. 41 is the fastest ashless filter paper, recommended for analytical procedures involving coarse particles or gelatinous precipitates (e.g., iron or aluminum hydroxides). Retention is 20 to 25 ¬µm. Also used in quantitative air pollution analysis as a paper tape for impregnation when determining gaseous compounds at high flow rates. This filter is also available in the Whatman Disposable Filter Funnel. This is a convenient, disposable 47mm filter funnel with a 250mL capacity. The 47mm Grade 41 filter can be easily removed for further analysis or culturing. 100 circles/box.