Description General description Especially useful where filter paper would be attacked by filtered material. Sintered discs with max. pore sizes in the range 40 to 100 μm are often used for preparative work and mercury filtration, 16 to 40 μm discs for analytical work with medium precipitates and 10 to 16 μm for fine precipitates. 1.0 to 1.6 μm discs are for ultra-fine filtration of biological solutions as they remove bacteria from liquids that would decompose if heated. Porosity chart for Duran filter funnels: Grade 2: 40-100 μm nominal max. pore size Grade 3: 16-40 μm nominal max. pore size Grade 4: 10-16 μm nominal max. pore size Grade 5: 1.0-1.6 μm nominal max. pore size Legal Information DURAN is a registered trademark of DWK Life Sciences