These cellulose filters are used in qualitative analytical techniques to determine and identify materials and for clarifying liquids. Particle Retention: 25µm Porosity: Coarse Filtration speed: Herzberg, 37 sec. Surface: smooth Extremely fast filtering with excellent retention of coarse particles and gelatinous precipitates such as ferric hydroxide and aluminum hydroxide Useful as a rapid filter for routine clean-up of biological fluids or organic extracts during analysis (100 per PK )