To Know Better Filter Paper Classification and Its Specific Usages

Filter Paper is a filter tool commonly used in chemical laboratories, and round filter paper is frequently seen and mostly made of cotton fibers. Therefore, there are countless small holes on the surface for liquid particles to pass through, while large solid particles cannot pass through, which allows separation of liquid and solid materials.

Filter paper can be qualitative and quantitative. In the application of analytical chemistry, after the inorganic compound is separated by filtration to separate out the precipitate, the residue collected on the filter paper can be used to calculate the loss rate during the experiment. After the qualitative filter paper is filtered, more cotton fibers are generated, so it is only suitable for qualitative analysis. Quantitative filter paper, especially the ash-free filter paper, can resist chemical reactions more effectively after a special treatment procedure, with fewer impurities, which is suitable for quantitative analysis.

In addition to filter papers for general laboratory applications, there are many applications for filter papers in daily life and engineering. Coffee filter paper is one of the widely used filter papers. The filter paper on the outer layer of tea bags provides high softness and high wet strength. Others use air filter paper for testing suspended particles in the air, and fiber filter paper for different industrial applications.

Qualitative filter paper
Qualitative filter paper is a filter paper commonly used in the chemical laboratory to filter precipitates and suspended matter. Cotton pulp or refined sulphate wood pulp is used as raw materials. After being beaten in free form, the fiber is then impregnated with hydrochloric acid for purification treatment. It is made by low pressure pressing on a fourdrinier paper machine. The silicon content is higher than that of quantitative filter paper, and it has a certain amount of ash after burning.

According to the size of the filter paper aperture, it is divided into three types: fast, medium and slow. The ribbon marks on the packaging box are white, blue and red, which should be selected according to different types of precipitation. For filtering colloidal precipitates such as iron hydroxide, the fast type should be used; when filtering fine crystal types such as barium sulfate precipitates, the slow type should be used.

Quantitative filter paper
The pulp is treated with hydrochloric acid and washed with distilled water to remove most impurities, during the quantitative filter paper manufacturing process. Therefore, there is little residual ash after burning, which has little effect on the analysis results, suitable for precision quantitative analysis.

Quantitative analysis of filter paper is also divided into three categories: fast, medium and slow. Filter belts are classified by white belt (fast), blue belt (medium speed), and red belt (slow speed).
White belt (fast): Paper tissue is soft and has the fastest filtration speed, suitable for retaining coarse precipitates, such as iron hydroxide, etc.
Blue belt (medium speed): The paper is densely packed and the filtration speed is moderate. It is suitable for retaining medium fine precipitates, such as zinc carbonate, etc.
Red belt (slow speed):The paper has the densest tissue and the slowest filtering speed, and is suitable for retaining fineness over precipitates, such as barium sulfate, etc.

There are two types of filter paper: circular and square. The regular specifications of circular filter paper are 70, 90, 10, 125, 150, 180, 55, 47 and 185, and others include 240, 270, 300. Square quantitative filter paper is 60cm*60cm and 41cm*45cm.