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
Ashless Grades (Ash 0.007%)
These standard ashless grades are high purity filter papers suitable for routine quantitative gravimetric techniques and in the preparation of samples for use in analysis involving instrumental techniques.
Ahlstrom 74: 2.0µm – Medium Speed
This grade has medium flow rate and good particle retention and is the most commonly used acidwashed filter. Ahlstrom 74 covers a wide range of general ashless filtration applications. It is used for gravimetric analysis of numerous components (e.g.: cements, copper, clay, bismuth, silicon, iron) found in heavy industries such as construction, mining or steel. Ahlstrom 74 is also used as a high purity filter for speedy filtering of trace elements such as silver chromate, lead sulfate, zinc and ammonium hydroxides. Ahlstrom 74 is also found in general soil analysis for separating solid from aqueous extracts.
Environmental Laboratory Applications:
STM 3500-Li Lithium Detection: Flame Emission Photometric Method
During sample preparation, the liquid may be filtered through a medium-porosity paper, such as Grade 74, to suppress ionization.
STM 5520.B-D Oil and Grease: Partition- Gravimetric Method, Partition-Infrared Method, Soxhlet Extraction Method
During the separation process of the partition methods, the sample is filtered through Grade 74. This grade is also used in the Soxhlet method to collect the oil and grease prior to extraction.
Mining Laboratory Applications:
ASTM E316-11 Determination of Iron in Manganese Ore
This precipitate is larger and requires a medium retention, medium flow ashless grade. Grade 74 is the recommended media.
ASTM D2492-02 Forms of Sulfur in Coal
Grade 74 is used during the initial extraction and to determine the percent of pyritic sulfur. Grade 54 and Grade 94 are used to determine the percent of sulfate sulfur.
ASTM D5263-93 Determining the Relative Degree of Oxidation in Bituminous Coal by Alkali Extraction
The amount of humic acid present in coal correlates to the degree of oxidation. Because of the high solids loading, and presence of fines, the test recommends using a bi-layer filter. Grade 74 is used as the pre-filter and Grade 94 as the main filter. This will provide the necessary filtration and ash properties needed for the procedure.
Construction Laboratory Applications:
ASTM C114-11b Chemical Analysis of Hydraulic Cement
Hydraulic Cement is tested for the presence of multiple elements with this procedure. Quantitative filters, Type II ASTM 832 E, F and G (Ahlstrom Grades 54, 74, and 94 respectively) are recommended for various steps in the process.
ASTM D-425-88 Centrifuge Moisture Equivalent in Soils
The moisture equivalent and porosity is used to give an estimate on aquifer storage coefficient. A dry sample of soil is placed in a gooch crucible that is lined with Grade 74, which is then placed in a water bath till the soil reaches stable saturation. The paper works as both a wick and barrier.
ASTM D4542-07 Pore Water Extraction and Determination of Soluble Salt Concentration of Soils by Refractometer
The salt concentration of the water in the soil is tested with this method. The sample is placed in a press with Grade 74. The sample is compressed and the extracted water collected and tested with a refractometer.