Pure cellulose grades. Thin papers include Grade 3MM Chr, 1 Chr, 2 Chr, 4 Chr, 17 Chr, 20 Chr and 17 Chr. Specifications for each grade are as follows; 3MM Chr: Though widely used as a blotting paper, 3MM Chr is used in both electrophoresis and for general chemistry. A medium thickness paper (0.34 mm) used extensively for general chromatography and electrophoresis. Flow rate is 130 mm/30 min. Grade 1 Chr: Thickness 0.18mm. Flow rate (water) 130mm/30min. The world standard paper for chromatography. One of the thinnest papers, with medium flow rate. Smooth surface. Good resolution. Suitable for general analytical separations. Grade 2 Chr: Thickness 0.18mm. Flow rate 115mm/30 min. Slower than 1 Chr, for higher resolution applications. Smooth surface. Particularly recommended for optical or radiometric scanning. Grade 4 Chr: Thickness 0.21mm. Flow rate 180mm/30 min. Fastest thin paper. Recommended for routine and/or repetitive chromatography when loadings are relatively low. Smooth surface. Very suitable where speed is important and very high resolution is not required (as in routine quality control applications). Grade 17 Chr: A thick (0.92 mm) and highly absorbent paper with a very high flow rate of 190 mm/30 min. Suitable for the heaviest loadings and ideal for preparative paper chromatography and electrophoresis. Grade 20 Chr: Thickness 0.17mm. Flow rate 85mm/30min. For maximum resolution, this grade is supreme, giving the greatest possible separation of closely related compounds. Smooth surface. Recommended for separation of samples of unknown composition, with outstanding resolution at low loadings. Grade 31ET Chr: Thickness 0.50 mm. Flow rate 225 mm/30 min. Extremely fast. Flow rate is the highest of all chromatography papers in the Whatman range. Thick paper with fairly soft surface. Principal application is in electrophoresis of large molecules.