Ahlstrom manufactures a series of extremely high purity, acid washed filter papers designed for use in analytical and gravimetric analysis. The quantitative grades are manufactured from top quality cotton linters using ultra-pure, reverse-osmosis water and are further treated with dilute acid to remove any remaining organic and inorganic impurities. All quantitative grades are manufactured in a strictly controlled environment that ensures high uniformity and high purity from filter to filter. Hardened ashless grades (ash 0.006 percent): 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. Ahlstrom 95: 1.5 micrometer -slow speed: This is an extremely fine retention filter for critical gravimetric analysis and metal determination of very fine particles such as barium and lead sulfates, stannic and nickel sulfide, calcium oxalate and calcium fluoride. 458 sec/100mls Filtration speed herzberg. 15 mls/min Filtration speed rapidity. Medium loading capacity.