Why should the filter paper be lower than the edge of the funnel when filtering

to prevent filtrate loss.

The filter paper must be folded in accordance with the angle of the funnel so that it fits snugly against the wall of the funnel and moistened with water. The edge of the filter paper should be about 5 mm lower than the mouth of the funnel, and the liquid level in the funnel should be slightly lower than the edge of the filter paper to prevent solids from mixing into the filtrate.

When filtering, the beaker spout containing the filtrate is close to the glass rod, and the liquid flows into the filter along the glass rod; The end of the glass rod is close to the three layers of filter paper; The nozzle at the lower end of the funnel is close to the inner wall of the beaker used to hold the filtrate; The filtered liquid flows into the beaker along the neck of the funnel and the inner wall of the beaker in a thin stream.

When filtering, the filter paper absorbs the filtrate. When the filter paper is wet, it will become soft. If the filter paper is higher than the edge of the funnel, the filter paper will be deformed, and the filtrate will seep out if it cannot fit snugly to the funnel, resulting in filtrate loss, which has a direct impact on the experimental analysis.

To prevent the solution from spilling out of the funnel, the filter paper is absorbent, and if the filter paper exceeds the part of the funnel that absorbs water, the solution may overflow.

Imagine what happens if the filter is higher than the funnel surface. Does the liquid come out? You can try it at home, what will the result be?

A In the filtration operation, the liquid level should always be lower than the edge of the filter paper, so A is correct;

b In the filtration operation, the edge of the filter paper should be lower than the edge of the funnel, so B is correct;

c In the filtration operation, the nozzle at the lower end of the funnel should be close to the inner wall of the beaker, so c is correct;

d In the filtration operation, the glass rod is close to the side of the three-layer filter paper, so d is wrong; Therefore, d

This operation is because the filter paper can be applied to form a "water column" at the outlet pipe of the funnel to improve the filtration speed;

What are the requirements for the filter paper in the Brinell funnel during suction filtration? Why.

Before filtration, be familiar with the structure and connection of the Brinell funnel, put the cut filter paper in, the diameter of the filter paper should not be greater than the bottom edge of the funnel, otherwise the filter paper will be folded, and the filter file will flow through the folded branch brother to cause loss, after the filter paper is wetted, you can pour part of the filtrate first (do not pour the solution into it at one time) to start the water circulation pump, adjust the vacuum degree through the two-way piston on the buffer bottle (safety bottle), and the vacuum degree can be lower at the beginning, so that the filter paper will not be broken by burying, and the remaining solution will be poured in after the filter cake has been formed into a layerAt this time, the vacuum level can be gradually increased until it is "dry".

The reason why the filter paper can not be higher than the edge of the funnel is to avoid the filter paper absorbing the filtrate during filtration, and the wet filter paper becomes soft, and the filter paper will be deformed, and the filtrate will seep out at the same time when it cannot be attached to the funnel, resulting in filtrate loss, which has a direct impact on the experimental analysis.

Filtration is the process of purifying the fluid through a special device, there are many ways of filtration, and the substances used are also very wide, solid-liquid, solid-gas, large particles, and small particles are very common.

Filtration is the heat generated by a suspension (or containing solid particles) under the action of a driving force or other external force.

The operation of separating solids and other substances from liquids (or gases) by separating solids and other substances from liquids (or gases) by penetrating the medium, and solids and other substances being trapped by the filter medium.

One sticker

Moisten the filter paper and stick it to the inner wall of the funnel without air bubbles remaining. (Prevent air bubbles from slowing down the rate of nucleation filtration).Two low

1. The edge of the filter paper is slightly lower than the edge of the funnel;

2. The liquid level is lower than the edge of the filter paper. (to prevent unclean liquid filtration).Three by the eye

1. Beaker when pouring.

The rim of the cup should be close to the glass rod;

2. The lower end of the glass rod is against the bend of the three-layer filter paper;

3. The nozzle on the side of the lower end of the funnel is close to the inner wall of the beaker.

The filter paper plays the role of filtration.

If the turbid liquid passes through the filter paper strictly.

Then the filtrate is clear.

However, if the filtration process is too fast, the filtrate level is higher than the filter paper surface.

Then it is possible that the filtrate will flow directly into the beaker below over the filter paper and into the beaker below.

The edge of the filter paper is higher than the mouth of the funnel.

This is to prevent the filtrate from getting higher than the filter paper.

So that the filtrate passes strictly through the filter paper.

Agree with the statement on the 2nd floor, and add the details:

1 The filter paper works on the part of the single layer, which must be close to the funnel, and the multi-layer part is only leaning on the glass rod, which is not easy to break; Reed segments.

2 Why the filter paper should be close to the funnel is to use the vacuum effect of the liquid to help "suck" the liquid to the filter paper. If you don't stick close, you won't really be stuffy, and you can only rely on the liquid to slowly penetrate it. There is also a requirement to form a water column at the funnel neck, also in order to create as much vacuum as possible under the filter paper.

If the filter paper is larger than the porcelain surface of the funnel, the filter paper will be folded, so that the filtrate will be sucked into the bottle from the edge of the filter paper during the filtration, resulting in crystal loss.

The correct operation is: trim the filter paper so that it is slightly smaller than the Brinell funnel, but cover all the holes, and moisten the filter paper with distilled water dropwise, and slightly open the suction valve to make the filter paper and the funnel tightly connected.

After wetting the filter paper, part of the filtrate can be poured into the water circulation pump first, and the vacuum level can be adjusted by the two-way piston on the buffer bottle. At the beginning, the vacuum degree can be lower, so that the filter paper will not be broken, and the remaining solution will be poured in after the filter cake has been closed and sold a layer, and the vacuum degree can be gradually increased until it is "dry".

When filtering, the filter paper is lower than the edge of the funnel to ensure that the liquid is filtered cleanly, to prevent liquid loss, and to prevent liquid from overflowing.

If the filter paper is not lower than the edge of the filter paper, the liquid may enter the beaker along the gap between the filter paper and the funnel, which will affect the filtration efficiency.

In addition, the filter paper is absorbent, if the filter paper is placed higher than the funnel, the support strength of the filter paper will become lower after water absorption, the filter paper may be deformed, can not fit the funnel, and will also make the filtrate seep, resulting in filtrate loss, which has a direct impact on the experimental analysis.

A In the filtration operation, the liquid level should always be lower than the edge of the filter paper, so A is correct; b In the filtration operation, the edge of the filter paper should be lower than the edge of the funnel, so B is correct; c In the filtration operation, the nozzle at the lower end of the funnel should be close to the inner wall of the beaker, so c is correct; d In the filtration operation, the glass rod is close to the side of the three-layer filter paper, so d is wrong; Therefore, d