In chemistry, we call the separation of solids and liquids filtration. In the filtration operation, filter paper is indispensable. The filter paper functions to filter out solids and filter liquids.
The filter paper for laboratory use is one of the common lab consumables. It is normally round in shape. It is often made from cotton fiber and used to filter components. The functional principle of the filter paper is separating the substances through them. The filter papers are normally made from fiber, which is the reason that there are keyholes on them. The keyholes resist the big solid particles and provide pathways for the liquid particles.
The different kinds of filter papers having different characters are made by different technics. So, what are the main factors in the filter paper selection? There exist four: hardness, filtration efficiency, capacity, and applicability.
Filter paper structure
The filter paper is directional. The front side of the filter paper has loose fibers; the mesh surface of the filter paper has tight fibers. The front pores are in the shape of a bell mouth, and the pores become smaller along with the thickness of the filter paper. The thickness of the filter paper is about 0.35～0.5mm, and the particle size of dust particles varies from ranging from a few microns to tens of microns.
Filter paper filtration not only has the function of a screen but also has the function of deep filtration; the side magnification shows that the filter paper is a multi-layer structure.
The front of the filter paper should face the direction of airflow. The screen surface of the filter paper should be in the direction of the gas flow. Color lines are drawn on the screen surface to facilitate user identification and prevent mistakes; if the front and back directions are wrong, the filter element is in use, and dust is stored. Ability is reduced by 30%.
Types of filter paper
Generally, the filter paper types are qualitative filter paper and quantitative filter paper. The qualitative filter paper is often used in qualitative analysis. The reason is that the qualitative filter paper produces more cotton fibers if it is filtered. The quantitative one is dealt with the particular process, which makes the paper not react with the common chemicals, in the production. As a result, it produces fewer impurities and is used in quantitative analysis.