This is a fast filtering grade for gravimetric analysis of coarse particles and gelatinous precipitates (i.e.: aluminum and zirconium hydroxides) in acid and alkali solutions. Ahlstrom 55 is also used in air and foodstuffs analysis and for chloride and phosphorous in cement, coal and coke.

These specially treated hardened ashless grades are available for critical quantitative analytical techniques requiring increased wet-strength and handling capacity. These high purity filter papers have a tough, smooth surface free of loose fibers and are ideal for collecting wet precipitates. Each grade offers a convenient combination of particle retention and flow rate and are generally used because of their high chemical resistance to strong acid and alkali.