This 15 µm, Medium Speed grade is used for the filtration of coarse particles and gelatinous precipitates such as ferric aluminum and magnesium hydroxides. Grade 631 is used in air monitoring and gas filtration when high flow rate is needed. This grade is also found in routine cleanup analysis of insoluble liquids such as biological fluids and organic elements.
Ahlstrom-Munksjö 631- 15 µm, Medium Speed
Equivalent to Whatman Grade 4 or 4CHR.
Please note the below grid is a recommendation of what diameter filter paper is compatible with glass or plastic filter funnels.
| Diameter of filter funnel (mm) | Diameter of filter paper required (mm) |
| 35 | 55 |
| 45 | 70 |
| 55 | 90 |
| 65 | 110 |
| 75 | 125 |
| 90 | 150 |
| 100 | 185 |
| 125 | 215 |
| 150 | 240 |
| 180 | 320 |
| 220 | 400 |
| 260 | 500 |
When folded into a cone (typically in quarters), it should fit inside the funnel with about 5–10 mm extending above the rim for easy handling.
What is filter paper used for?
Filter paper is used to separate solids from liquids or gases, acting as a semi-permeable barrier that allows certain substances to pass through while retaining others. It's commonly used in laboratories for various applications, including filtration, sample preparation, and analysis.