These are the supreme quantitative filter papers featuring high wet strength and chemical resistance. These papers are acid-hardened, which reduces ash to an extremely low level. The tough surfaces of these fillters make them suitable for a wide range of critical analytical filtration operations. Each grade offers a convenient combination of filtration speed and particle retention. Grade 541: 22μm. Fast filtration of coarse particles and gelatinous precipitates in acid/alkali solutions during gravimetric analysis. Typical applications include determining fibre in animal foodstuffs, gelatin in milk and cream, chloride in cement, and chloride and phosphorous in coal and coke. Hardened ashless: 0.006% ash maximum. These filters are acid-hardened to give high wet strength and chemical resistance with extremely low ash content. The tough surface makes these filters suitable for a wide range of critical filtration procedures.