No. 40 Quantitative Ashless Paper

Most widely used general purpose gravimetric filter paper; acid washed, ash content 0.007%
Medium speed and retention (8 µm); rough surface
Used for calcium oxalate, silica in steel and well-digested barium sulfate; as a high-purity filter in the collection of trace elements and radionuclides in the atmosphere
Used as a support for x-ray fluorescence and as a sample carrier for Shoeniger combustion