Whatman No. 40

Excellent quantitative paper for all general purposes. ASTM initial speed of filtration is 75 seconds. Will retain medium 8 µm, crystalline precipitates. Frequently used in gravimetric analysis. For calcium oxalate, CaC2O4, this filter paper is recommended. Used frequently as a carrier for separation of rare earth metals, for silica in steel, well digested barium sulfate. Loading capacity is normal. Ash content is 0.11 mg per 12.5 cm circle. (For cost savings, see Ahlstrom equivalent, 445-500-02 Series)