For medium speed and retention, Ashless Grade 40 (8µm) is typically used for analysis of components in clays, cements, iron and steel products, or as a primary filter for separating solids from aqueous extracts in soil analysis, or to determine quantitative sediments in milk.
Fastest filter paper, Ashless Grade 41 (20-25µm), is recommended for analysis of coarse particles or gelatinous precipitates (iron or aluminum hydroxides). Also useful as a rapid filter for routine cleanup of biological fluids or organic extracts during analysis.
Use Hardened Low Ash Grade 50 (2.7µm) Filters, the thinnest of Whatman papers, for qualitative or quantitative filtrations that require vacuum assistance on Buchner or 3-piece filter funnels. Slow flow rate.
Use Hardened Ashless Grade 541 (20-25µm) for fast filtration of coarse particles and gelatinous precipitates in acid/alkali solutions during gravimetric analysis, such as fiber in animal foodstuffs, gelatin in milk and cream, chloride in cement, and chloride and phosphorous in coal and coke. Box of 100.