How To Choose Filter Paper

Filter paper is divided into two types: qualitative filter paper and quantitative filter paper. According to the degree of tightness, qualitative filter paper and quantitative filter paper are divided into three types: fast, medium, and slow. Due to the high content of ash in qualitative filter paper, it is often used for precipitation or residue filtration without the need for burning and weighing. Quantitative filter paper is used in precipitation weight analysis. Due to the treatment of quantitative filter paper with hydrochloric acid and hydrofluoric acid, the ash content after burning is extremely low and can be ignored, so it is also called ash free filter paper.

Selection of filter paper: Generally speaking, for the filtration of amorphous precipitates such as Fe (OH) 3 and Al (OH) 3, loose and fast filter paper can be used to avoid slow filtration speed; For fine crystalline precipitates such as CaC2O4 and BaSO4, tight slow filter paper should be used to prevent sediment leakage. Medium sized crystalline precipitates, such as K2SiF6, SiO2, etc., can use medium speed filter paper. The size of filter paper should be selected based on the amount of sediment. In the analysis of cement and its raw materials, a circular shape with a diameter of 9-11cm is sufficient.