According to the different degree of tightness, qualitative filter paper and quantitative filter paper can be divided into three kinds: fast, medium and slow. Because qualitative filter paper contains more ash, it is often used for precipitation or residue filtration without burning weighing.
Quantitative filter paper is used in precipitation weight analysis. Because the quantitative filter paper has been treated with hydrochloric acid and hydrofluoric acid, the ash content after burning is negligible, so it is also called ashless filter paper.
The following are the specific methods for choosing filter paper:
Generally speaking, the filter paper of amorphous precipitation (such as Fe (OH) 3 and Al (OH) 3) can be chosen loosely so as to avoid too slow filtration speed. For fine-grained precipitation such as CaC2O4 and BaSO4, close slow-speed filter paper should be selected to prevent precipitation leakage.
Medium-sized crystalline precipitation, such as K2SiF6 and SiO2, can be selected as medium-speed filter paper. The size of the filter paper should be selected according to the amount of sediment. In the analysis of cement and raw materials, the circular filter paper with a diameter of 9-11 cm should be selected.
没有评论:
发表评论