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Experimental considerations for filtration operations.

Bucket rack beaker glass rod, filter paper funnel angle the same. Before filtering, let it stand, and don't forget to lean three and low two low.

Explanation: 1. The beaker glass rod of the bucket rack, the same funnel angle of the filter paper:"bucket"Refers to the funnel; "rack"Refers to the funnel frame.

These two sentences describe the instruments needed for the filtration experiment: funnel, funnel holder, beaker, glass rod, filter paper, and emphasize that the filter paper should be folded at the same angle as the funnel (so that the filter paper fits snugly against the funnel wall). If there are air bubbles, you can use a glass rod to drive away the air bubbles, taking care not to break the filter paper.

2. Stand before filtration: It means that the liquid must be left for a while before filtration, so that the solid and liquid can be fully separated.

3. Don't forget to rely on three and two low: It means that don't forget to rely on three and two low when filtering. "Three by the eye"It means that the end of the funnel neck should be leaned against the wall of the beaker that accepts the filtrate, the glass rod should be rested against the filter paper, and the beaker spout containing the filtrate should be leaned against the glass rod; "Two low"This means that the edge of the filter paper should be slightly lower than the edge of the funnel, and the liquid level of the filtrate poured should be slightly lower than the edge of the filter paper.

One sticks, two low, three leaning.

One sticker: The filter paper fits snugly to the funnel.

Two low: the filter paper is lower than the edge of the funnel; The liquid level is lower than the filter paper.

Three leanings: the beaker of pouring liquid is against the upper end of the glass rod; The lower end of the glass rod is close to the three layers of filter paper; The lower end of the funnel is next to the beaker containing the liquid.

In the operation of chemical experiments, the attention to be paid to filtration is summarized as "one paste, two low, three leaning" and "one stick": the filter paper should be close to the inner wall of the funnel; "Two low": 1 The edge of the filter paper is lower than the edge of the funnel 2 The liquid level in the funnel is lower than the edge of the filter paper; Three by the eye

1 The mouth of the beaker for pouring the liquid should be close to the glass rod 2 The end of the glass rod should be close to the side with three layers of filter paper 3 The end of the funnel should be close to the inner wall of the beaker that receives the filtrate;

In addition, it should also be noted that: 1. Filtration must be drained with glass rods, and the filtrate cannot be poured directly into the funnel;

2. The filter paper should be intact and undamaged, otherwise the filtration effect will be affected;

3. The beaker that undertakes the filtrate should be clean, otherwise the obtained filtrate will be polluted, so it should be filled in: summarized as "one sticker, two low, three leaning" and "one sticker": the filter paper should be close to the inner wall of the funnel; "Two lows":

1 The edge of the filter paper is lower than the edge of the funnel 2 The liquid level in the funnel is lower than the edge of the filter paper; "Three supports": 1 the mouth of the beaker for pouring the liquid should be close to the glass rod 2 the end of the glass rod should be close to the side with three layers of filter paper 3 the end of the funnel should be close to the inner wall of the beaker receiving the filtrate;

Do you know the precautions for filtration?

One sticks, two low, three leaning.

One sticker: The filter paper is close to the inner wall of the funnel.

Two low: the edge of the filter paper is lower than the edge of the funnel; The end of the glass rod drain is lower than the edge of the filter paper.

Three-leaning: the mouth of the beaker containing the solution to be filtered rests against the glass rod; The glass rod rests against the side of the three-layer filter paper; The lower mouth of the funnel rests against the inner wall of the beaker containing the filtered solution.

When filtering, the glass rod is opposite the beaker spout containing the filtrate; The end of the glass rod is close to the three layers of the filter paper in the funnel, but the filter paper cannot be touched; To keep it vertical; The neck tip of the funnel is close to the inner wall of the beaker that receives the filtrate. The liquid transferred at a time should not exceed two-thirds of the height of the filter paper to prevent the filtrate from flowing out of the walls without passing through the filter paper. For liquids and solids remaining in the beaker, they should be rinsed with solvent or distilled water in small quantities and multiple times, and all the lotion should be transferred to a funnel for filtration.

It is necessary to achieve "one stick, two low, and three reliance". (See photo).

Filter cloth bags. Even if the filter paper is wet, it will stick to the inner wall of the funnel and leave no air bubbles.

Prevents air bubbles from slowing down filtration. "Two lows":

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.

Prevents unclean liquid filtration. Three by the eye

1 When pouring, the beaker containing the filtrate is next to the glass rod.

Filter sponge. 2 The lower end of the glass rod is against the three layers of filter paper.

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

Precautions. 1 The mixture in the beaker should be stirred with a glass rod before straining and then filtered.

2 If the solution is still turbid after filtration, it should be filtered again until the solution becomes transparent.

Filter cartridge 3Washing method of precipitation in the filter: add distilled water to the filter with a flask or dropper, so that the water surface cover is free of sediment, and after the solution is all filtered out, repeat 2 3 times.

4. When doing purification experiments, it is necessary to extinguish the water before it evaporates, otherwise the crystals will radiate and harm the human body.

The water is not thoroughly filtered and contains impurities.

Moisten the edge of the filter paper with distilled water with a glass rod so that it fits snugly against the funnel wall1 Definition: Filtration is a method of separating a solid substance dissolved in a liquid from a liquid.

2 Principle: When filtering, the liquid passes through the small holes in the filter paper, while the solid substance remains on the filter paper, thus separating the solid and liquid.

3 How to Operate:

For example: Coarse Salt Purification (Ask students to design an experimental procedure) Demonstrate coarse salt so that students can see insoluble solid substances such as sand on coarse salt to facilitate students' thinking.

Demonstration experiment) coarse salt purification.

Summarize: 1) Steps:

Dissolve the coarse salt in a beaker.

Filtering (2) Precautions:

One sticker: The filter paper is close to the inner wall of the funnel.

Two low: the filter paper is lower than the edge of the funnel;

The filtrate is lower than the edge of the filter paper.

Three-leaning: The lower end of the funnel is close to the inner wall of the beaker.

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

The beaker rests against the rod and pours the liquid.

3) The role of the glass rod.

Dissolution – Accelerates dissolution.

Filtration – drainage.

Filtration is a method used to separate intolerant solids from soluble solids.

Moisten the filter paper with water; Principle: Harness the surface tension of water!

Even if the filter is not broken, it is best not to wash it, unless you are sure that it will be thoroughly cleaned, and the performance will not change after cleaning, and you have the means to prove it.

The filter material of the ventilation filter above F6 efficiency is generally in between, it is not strong, and it cannot withstand rubbing, therefore, most of the filters above F6 are disposable. In fact, if you look at the filter media, you can tell if it can be cleaned or not.

Traditionally, cleaning is done by rinsing with water or rubbing by hand. Therefore, the media of the washable filter should be strong and the fibers should be coarse (diameter F10). Most of these filter materials are inexpensive nonwoven fiber felts, which are ideal materials for the manufacture of G2 G4 efficiency filters.

Of course, you also have to judge whether the auxiliary materials of the filter are water resistant.

More than 20 years ago, there was a foam plastic filter in China, which could be cleaned, but its filtration effect was too poor, and now it is rare. Nylon mesh and metal mesh can be cleaned, but people in the filter industry say that it is "mosquito repellent" and does not belong to the filter.

Due to the high labor intensity, high labor costs, and the relatively low cost of the filter, users in developed countries rarely clean the filter, although some can be cleaned in principle. In recent years, many domestic users no longer worry about the cleaning of filters.

Most of the "electret" materials used for air filtration are hydrophobic chemical fiber materials, and in general, water does not destroy the static electricity on the "electret" material. However, the addition of cleaning agents may have an effect on static electricity. To be on the safe side, when considering cleaning filters with electrostatic materials, it is necessary to perform some experiments to confirm that water and cleaning agents have no effect on the filtration effect.

Ultrasonic cleaning is a good idea to use the ultrasonic principle to clean the filter. There is no rubbing during ultrasonic cleaning, and the filter material is generally not damaged.

One sticker: refers to the filter paper should be close to the funnel wall, generally when the filter paper is pasted on the funnel wall, wet with water and squeeze out the bubbles, because if there are air bubbles will affect the filtration speed.

Two low: first, the edge of the filter paper should be slightly lower than the edge of the funnel; Second, throughout the filtration process, it is necessary to always pay attention to the liquid level of the filtrate to be lower than the edge of the filter paper.

Otherwise, the filtered liquid will flow down from the gap between the filter paper and the funnel and flow directly to the receiver at the bottom of the funnel, so that the unfiltered liquid is mixed with the filtrate, and the filtrate is turbid, and the purpose of filtration is not achieved.

Three close together: first, when the liquid to be filtered is poured into the funnel, the beaker spout of the beaker containing the liquid to be filtered should lean against the inclined glass rod (glass rod drainage); The second is that the lower end of the glass rod should be leaning on the side of the three-layer filter paper (one side of the three-layer filter paper is thicker than the one layer of filter paper, and the three-layer filter paper is not easy to be broken); The third means that the neck of the funnel should be close to the inner wall of the receiver receiving the filtrate.

Common filtration methods.

1. Atmospheric pressure filtration, the instruments used are: glass funnel, small beaker, glass rod, iron frame, etc. The issues to be aware of are:

When stacking the filter paper, try to keep it close to the inner wall of the glass funnel, which will form continuous water droplets and speed up the filtration speed. This is not so obvious in general filtration as it is slow in medicineThere is a big difference when the collection and sorting of the education network is required to be filtered with heat. For example, when preparing KNO3, if your speed is too slow, it will be cooled in the funnel and part of the KNO3 will precipitate out and block the funnel mouth, so the experimental effect will be less than ideal.

2. Vacuum filtration, the instruments used are: Brinell funnel, suction filter bottle, filter paper, bottle washing, glass rod, circulating vacuum pump, etc. The issues to be aware of are:

When choosing the filter paper, it should be moderate, when the suction filter bottle is connected with the circulating vacuum pump, the filter paper is wetted with a washing bottle, and then the product to be filtered is transferred to it (if there is a solution part, a glass rod should be used to drain it).

In the operation of chemical experiments, the attention to be paid to in filtration is summarized as "one stick, two low, and three reliance".

"One stick": the filter paper should be close to the inner wall of the funnel.

Two lows": 1The edge of the filter paper is lower than the edge of the funnel.

2.The liquid level in the funnel is lower than the edge of the filter paper.

Three reliance": 1The beaker where the liquid is poured should be held against the glass rod.

2.The end of the glass rod is next to one side with three layers of filter paper.

3.The end of the funnel is immediately against the inner wall of the beaker that receives the filtrate.

In addition, there are:

1.Filtration must be drained with glass rods, and the filtrate cannot be poured directly into funnel 2The filter paper should be intact and undamaged, otherwise it will affect the filtration effect3The beaker that receives the filtrate should be clean, otherwise the resulting filtrate will be contaminated, and if you think it is possible, please adopt it.

The key points of operation are: one sticker, the filter paper is close to the inner wall of the funnel, the second is low, the filter paper is lower than the funnel mouth, and the solution is lower than the filter paper. Three leaning, the glass rod is close to the three-layer filter paper, the small beaker is close to the glass rod, and the lower funnel mouth is close to the inner wall of the large beaker.

First of all, you need to understand what are the components of the substances in the experiment you are doing, then you need to understand what reactions will be produced by each process chemistry, which ones will have priority reactions, what products are after the reaction, and finally you are determining the chemical formula of the final filter residue according to the chemical reaction formula (pay attention to the influence of air, water, etc. on the chemical reaction).

It can be considered from the following aspects:

Generated precipitates or other insoluble substances.

The remaining solids of the reaction (after the reaction of excess Fe with dilute hydrochloric acid, the remaining Fe) and the original insoluble impurities (sediment in crude salt purification) before the reaction Soluble crystallization (such as saturated solution cooling).