Whatman* Quantitative Filter Papers, Ashless Grades (Ash 0.007%)

Grade 40 Ashless: 8 µm
The classic general purpose ashless filter paper with medium speed and retention. Typical applications include gravimetric analysis for numerous components in cements, clays, iron and steel products; as a primary filter for separating solid matter from aqueous extracts in general soil analysis, quantitative determination of sediments in milk and as a pure analytical grade cleanup filter for solutions prior to AA spectrophotometry. Used also as a high purity filter in the collection of trace elements and radionuclides from the atmosphere.
Grade 41 Ashless: 20-25 µm
The fastest ashless filter paper, recommended for analytical procedures involving coarse particles or gelatinous precipitates (e.g., iron or aluminum hydroxides). Also used in quantitative air pollution analysis as a paper tape for impregnation when determining gaseous compounds at high flow rates.
Grade 42 Ashless: 2.5 µm
A world standard for critical gravimetric analysis with the finest particle retention of all Whatman cellulose filter papers. Typical analytical precipitates include barium sulfate, metastannic acid and finely precipitated calcium carbonate.
Grade 43 Ashless: 16 µm
Intermediate in retention between Grades 40 and 41, and twice as fast as Grade 40. Typical applications include foodstuffs analysis; soil analysis; particle collection in air pollution monitoring for subsequent analysis by XRF techniques and inorganic analysis in the construction, mining and steel industries.
Grade 44 Ashless: 3 µm
Thin version of Grade 42 retaining very fine particles but with lower ash weight per sample and almost twice as fast as Grade 42.