What is filtration?

How filtration works

Filtration is a general term for a large group of unitary operations that purify fluids by means of special devices. There are many different types of filtration and a wide range of material systems are used, including solid-liquid, solid-gas, large particles, and small particles. In short, filtration is an operation in which the liquid (or gas) in suspension (or a fever gas containing solid particles) passes through a medium under the action of a driving force or other external force, and solid particles and other substances are retained by the filter medium, thus separating solids and other substances from the liquid (or gas).

The basic operation steps of filtration

1. The edge of the filter paper is slightly below the edge of the funnel.

2. The liquid level is lower than the edge of the filter paper. (To prevent the liquid from being filtered unclean.)

3. The mouth of the beaker should be close to the glass rod when pouring.

4. The lower end of the glass rod rests against the three layers of filter paper.

5. The long side of the bottom of the funnel is close to the inner wall of the beaker.

Notes on filtration

1. The mixture in the beaker should be stirred with the glass rod before filtering, and then filtered.

2. If the solution is still turbid after filtration, it should be filtered again until the solution becomes transparent. 3. Washing method for the precipitate in the filter: add distilled water to the filter with a flask or dropper, so that the water surface covers the precipitate, and repeat 2 to 3 times after the solution is all filtered out.

Reasons for failure of filtration

1. The filter paper is broken. 

① The lower end of the glass rod is close to a layer of filter paper. (The filter paper is punctured)

② The beaker holding the mixture is not close to the glass rod. (The filter paper is broken by the mixture)

2. The mixture did not pass through the filter paper.

Cause: The liquid level is higher than the edge of the filter paper. (The mixture flows directly from the gap between the filter paper and the funnel) or the apparatus is not clean.

①The lower end of the funnel is not clean

②The beaker below which the filtrate is collected is not clean

In both cases, the filtrate is cloudy.

Cangchen, a professional foundry filtration products manufacturer who focuses on the production, sales, service and solutions.