The difference between the front filter 20 cm and 40 microns There is a little difference between CM and Micron. generally Micron is the unit of filtering accuracy. what you said is that the filter is 20 cm long and the filtering accuracy is 40um.
[High school chemistry] filtration is one of the operation methods for separating solution and solid insoluble matter. The sediment needs to be washed if necessary. Add a small amount of distilled water to the filter No idea what the availability is, it should be soluble impurities. 'Availability' should be soluble, and 'soluble impurities' are other substances that can be dissolved in water and attached to precipitation. For example, filter calcium carbonate precipitation and calcium hydroxide solution, and wash out calcium hydroxide attached to the surface of calcium carbonate after filtration. at this time, calcium hydroxide is a 'soluble impurity '. If you don't understand, it should be a typo. it is an impurity soluble in water. after washing, it can be dissolved in water and separated from sediment. It's obviously a typo, soluble impurity! The title is wrong. it is soluble impurities.