Ahlstrom’s qualitative grades of filter paper are, by definition, recommended for use in analytical methods, which determine or identify particulate constituents of a mixture irrespective of the amount present. Qualitative filter papers are often used in routine separation work that still requires high purity and consistent performance. Ahlstrom offers a complete range of low ash filter papers for general laboratory work that provides you with the correct combination of particle retention, filtration speed, loading capacity and wet-strength. All our qualitative grades consist of > 95% super refined a-cellulose and linter fibers. Qualitative analysis Low ash content 0.06% Untreated Consistent performance Wet-strengthened grades available Custom cut Bulk packaging Standard Grades (Non Wet-Strengthened) Standard qualitative filter papers are suitable for quadrant folded or gravity flow applications. These grades contain a high level of alpha-cellulose that provides high purity but will weaken when wet. The inherent strength of standard (untreated) grades does not pose a problem when they are used in routine quadrant folded applications. We do not recommend these grades for use in vacuum work or when wet handling is required. Ahlstrom 613: 6µm – Medium Speed This is a strong filter paper with a medium flow rate and retention. Ahlstrom 613 is commonly used in student laboratories. This strong general-purpose filter is also useful in Buchner funnels for barium carbonate, lead chromate and beryllium hydroxides.