Filter Paper No. 40, Whatman

Grade 40: 8 μm (medium flow filter paper)
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 clean-up filter for solutions prior to AA spectrometry.

Also used as a high-purity filter in the collection of trace elements and radionuclides from the atmosphere.