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. Quantitative analysis Low ash content 0.007% (Acid-wash treated) High wet-strength Consistent performance Custom cut Bulk packaging Hardened Ashless Grades (Ash 0.006%) 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 55: 15µm – Fast Speed 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. Environmental Laboratory Applications: ASTM D4767-11 Test Method for Consolidated Undrained Triaxial Compression Test for Cohesive Soils (also a Construction Laboratory Application) The strength and stress-strain relationship of a cylindrical specimen of a saturated cohesive soil is tested with this method. Grade 55 is used both for a pre-filter before the porous disc and as strips on the side of the specimen that expedite the test. ASTM D5084-10 Test Methods for Measurement of Hydraulic Conductivity of Saturated Porous Materials Using a Flexible Wall Permeameter (also a Construction Laboratory Application) This method applies to measuring the hydraulic conductivity, or coefficient of permeability, when a one-dimensional, laminar flow of water moves through porous materials such as soil or rock. Grade 55 is typically used. STM 3500-PB Lead Detection: Dithizone Method Preparation of the dithizone includes filtering through a paper, such as Grade 94. During the sample digestion the sample is filtered through a leadfree filter paper, such as Grade 55. Construction Laboratory Applications: ASTM D2435-11 One-Dimensional Consolidation Properties of Soil The magnitude and rate of consolidation of soil is determined to estimate both differential and total settlement of a structure or earth fill. The sample is restrained laterally and drained axially while subjected to an applied, controlled stress loading. Grade 55 is used to prevent intrusion of the soil sample into the porous disc. ASTM D3999-11 Determination of the Modulus and Damping Properties of Soils Using the Cyclic Triaxial Apparatus The test is done using a Pore Water Pressure Measurement Device and a Triaxial Apparatus. Grade 55 is recommended in the saturation phase of the procedure. It functions as a dry drainage system.