A Brief Introduction Of Vacuum Filtration
Vacuum filtration is a physical term, also known as decompression filtration and vacuum filtration, which has double meanings. In physical terms, vacuum filtration refers to the method of reducing the pressure in the vacuum filtration bottle by using the vacuum pump to achieve the purpose of solid-liquid separation.
Buchner funnel, vacuum bottle, hose, vacuum pump, filter paper
First of all, the instrument shall be installed to check whether the connection between the Buchner funnel and the vacuum filter bottle is tight and whether the connection of the vacuum pump is leaking; the vacuum filter bottle is equipped with a single hole plug, and the Buchner funnel is installed in the plug hole. The inclined surface at the lower end of the funnel tube faces the air extraction nozzle. But it is not reliable to be too close, so as to avoid the filtrate being pumped away from the vacuum nozzle.
Trim the filter paper to make it slightly smaller than the cloth funnel, but cover all the holes, and drip distilled water to make the connection between the filter paper and the funnel close; add a small amount of water or solvent to the filter paper, turn on the tap gently, and suck part of the air in the vacuum bottle to make the filter paper close to the bottom of the funnel, so as to avoid solid entering the filtrate from the edge of the filter paper during the filtration process. The third step is to turn on the air pump switch and start vacuum filtration. In the process of vacuum filtration, when the solid layer in the funnel cracks, the glass plug, and other things shall be used to compress it and block the cracks.
If it is not pressed tightly, it will also reduce the efficiency of vacuum and filtration; if the solid needs to be washed, a small amount of solvent can be sprinkled on the solid, stand for a while, and then pump it dry. When taking out the solid from the funnel, remove the funnel from the vacuum filter bottle, hold the funnel tube with the left hand, turn it upside down, and “tap” the left hand with the right hand, so that the solid, together with the filter paper, falls onto the clean paper piece or surface dish. Remove the filter paper and dry the solid. The solution should be poured out from the top of the vacuum flask.
Matters needing attention
1. When the vacuum filtration is stopped, first unscrew the cock on the safety bottle to restore normal pressure and then close the air extraction pump
2. When the filtered solution has strong acidity, strong alkalinity or strong oxidation, use glass fiber instead of filter paper or glass sand funnel instead of Brinell funnel
3. It is not suitable to filter colloidal precipitation or precipitation with too small particles