Vacuum Filtration Device Operation

Vacuum filtration is a common laboratory technique used to separate a solid precipitate from a liquid solution by applying a vacuum to accelerate the filtration process. This technique is particularly useful when you want to separate a solid from a liquid quickly or when the solid particles are very fine and would take a long time to settle by gravity alone. Here’s how a vacuum filtration device operates:

Components of Vacuum Filtration Device

Filter Flask: A filter flask is a glass container with a sidearm that connects to a vacuum source. The liquid mixture to be filtered is poured into the flask.

Buchner Funnel or Hirsch Funnel: This funnel has a perforated plate at the bottom and a tapered stem. It is placed on top of the filter flask. The funnel holds the filter paper and supports the solid material while allowing the liquid to pass through.

Filter Paper: A circular piece of filter paper is placed inside the funnel. It helps trap the solid particles while allowing the liquid to pass through and be collected in the filter flask.

Rubber Stopper: A rubber stopper is used to seal the connection between the funnel and the sidearm of the filter flask, ensuring a vacuum-tight seal.

Vacuum Source: A vacuum pump or aspirator is connected to the sidearm of the filter flask. The vacuum source creates a pressure differential between the inside of the flask and the outside, causing the liquid to be drawn through the filter paper and funnel.

Operation of Vacuum Filtration Device

Preparation: When installing the instrument, the slope of the lower end of the funnel tube faces the suction nozzle. However, it is not reliable enough to prevent the filtrate from being pumped away from the suction nozzle. Check if the connection between the cloth funnel and the suction filter bottle is tight and if the air pump connection port is leaking。 Make sure the funnel is clean, the filter paper is properly positioned in the funnel, and the rubber stopper forms a tight seal.

Wetting the Filter Paper: Before adding the mixture to be filtered, trim the filter paper so that it is slightly smaller than the cloth funnel, but cover all the holes, and add distilled water to make the filter paper and the funnel tightly connected; This helps the filter paper adhere to the funnel’s surface and prevents small particles from passing through gaps.

Adding the Mixture: Carefully pour the liquid mixture to be filtered into the funnel while ensuring that it doesn’t overflow the funnel’s capacity.

Application of Vacuum: Turn on the air pump switch and start pumping. The reduced pressure inside the filter flask creates a pressure difference that pulls the liquid through the filter paper. The liquid passes through the filter paper, leaving behind the solid particles.

Collection: The liquid that passes through the filter paper is collected in the filter flask. The solid particles remain on the filter paper as a residue.

Drying or Further Processing: Once the filtration is complete, you can remove the funnel and filter paper containing the solid residue. Depending on your application, you might need to dry, weigh, or further process the collected solid material. If the solid needs to be washed, a small amount of solvent can be sprinkled onto the solid, allowed to stand for a while, and then drained.

Cleanup: After filtering, first remove the suction filter bottle and then close the suction pump, turn off the vacuum source, remove the rubber stopper, and disassemble the apparatus. When removing the solid from the funnel, remove the funnel from the filter bottle, hold the funnel tube with your left hand, invert, and “slap” your left hand with your right hand to allow the solid to fall on the clean paper or watch glass together with the filter paper. Remove the filter paper and dry the solid.

Precautions of Vacuum Filtration Device

1. The solution should be poured out from the top of the suction bottle.
2. When the suction filtration is stopped, first unscrew the cock on the safety bottle to return to normal pressure and then close the air pump.
3. When the filtered solution has strong acidity, strong alkalinity, or strong oxidizing property, replace the filter paper with glass fiber or replace the Buchner funnel with a glass sand funnel.
4. It is not advisable to filter the gelatinous precipitate or the precipitate with too small particles.
Wash the sediment: turn off the small faucet, immerse the precipitate, and let it flow down slowly. Circulating water vacuum pump

Vacuum filtration is a versatile technique used in various scientific fields, including chemistry, biology, and materials science, to separate solids from liquids efficiently and rapidly.