Can You Put Too Much Suction On A Filter Flask

Vacuum filtration

Figure 1 shows a setup for a vacuum (or suction) filtration using a Hirsch funnel. A vacuum filtration is usually faster than a simple gravity filtration. However, there are several points that accept to exist considered.

front: filter flask with neoprene adapter (the black or grey rubbery thing in your drawer) and Hirsch funnel

back: vacuum trap with T-bore stopcock and thick-walled tubing

A vacuum filtration is usually faster than a simple gravity filtration using a uncomplicated conical funnel. All the same, there are several points that take to be considered when performing a vacuum filtration. Due to the fact that reduced pressure level is used in this procedure, special attending has to be paid to the equipment used in this procedure. The glassware (i.eastward. filter flask) should non have any cracks on the sides or the bottom. It is also imperative that the filter flask and the vacuum trap are clamped securely, then that they do non move during the filtration. The thick-walled tubing tends to act like a whip sometimes, and slams the filter flask into the hotplate or other metal objects resulting in an implosion (or tips the flask over and the production is found after on the bench or even worse on the dirty floor!).

The clean filter flask and the vacuum trap consist of heavy-walled glassware. Thick-walled tubing should be used as well. Normal tubings that are used equally water hoses volition collapse when a vacuum is applied!

Never perform a vacuum filtration without a vacuum trap. It is also a good idea to go on the trap make clean, only in instance something gets sucked in in that location. Information technology is easier to recover it from a clean trap and then from a dirty trap.

Vacuum filtrations tin simply be performed with funnels that have a flat surface e.thou. Hirsch or Büchner funnel, which are both made from procelain! The filter newspaper has to encompass all holes in the bottom of the funnel and does not extend up the sides. This ways that the minor pieces (~i.3 cm) of filter paper are used for the Hirsch funnel, and not a bigger circle hanging in the funnel. If the filter paper has the incorrect size or not properly placed in the funnel, a significant function of the solid will "run through" the filter newspaper.

If the filter paper is too big for the Büchner funnel, it has to be cut to size with scissors. (From this betoken of view, it might be a skillful idea to generate a cardboard bare from an existing filter paper). The filter paper is moistened with the solvent that makes upwards the solution. This prevents the formation of multi-layer systems in the filter flask. It should attach well to the lesser before the vacuum is applied. Then the solution is slowly poured slowly into the funnel.

Figure two: Hirsch funnel with filter newspaper, all holes covered

Figure 3: B ü chner funnel with filter paper extending upwards the side.

When a funnel is placed on top of the filter flask, a neoprene adapter (the black or grayness "rubbery matter") or condom stopper is used to ensure a skillful seal between the filter flask and the funnel.

When the filtration is finished, the tubing from the filter flask should be removed before the vacuum is turned off. This is less of import when the firm vacuum line is used similar in the instruction lab, but it will be when an aspirator is used. The low pressure in the filter flask sucks the h2o back into the mother liquor, and if this is the part of involvement, the experimenter is in big trouble.

Also, a vacuum filtration is not suitable for solvents with depression boiling points e.g. diethyl ether, dichloromethane or other depression boiling solvents. The solvent evaporates nether the vacuum and the dissolved solids precipitate, clogging upwardly the pores of the filter newspaper and go stuck on the insides of the funnel i.e. stem, etc. The same applies to hot solutions, since the solvent is close to its humid point also. In those cases, gravity filtration is used.

If a very fine precipitate has to be filtered, it is advisable to use some filter aid similar diatomaceous earth or Celite. This will prevent that the holes of the filter paper will get clogged up as well fast. This technique is obviously not very useful if the solid is the interesting part, considering it volition be very time consuming to separate the product from the filter aid.

Important Pointers:

ane. Due to the fact that you are going to work with reduced force per unit area, special attending has to exist paid to the equipment used. The glassware (e.one thousand. filter flask) should not have any cracks. Information technology is too imperative that the filter flask and the vacuum trap are clamped securely, and so that they do non motility anywhere. The thick-walled tubing tends to human action like a whip sometimes, and slams the filter flask into the hotplate or other metal objects (which can cause an implosion), or just flips information technology over (and you product is on the bench or even worse on the dirty floor). Y'all probably don't have any desire to collect your product from the floor, practise you?

two. The filter flask and the vacuum trap consist of heavy-walled glassware. You should use thick-walled tubings every bit well. Normal tubing that yous utilize as h2o hoses will plummet nether vacuum. See link.

3. Never perform a vacuum filtration without a vacuum trap. It is also a good idea to keep the trap clean, just in instance something gets sucked in there, it is easier to recover information technology from a clean trap then from a muddy trap.

4. Vacuum filtration is just suitable for funnels with a flat surface! The filter paper has to cover all holes in the bottom of the funnel (Hirsch or Büchner, both made from procelain) and does not extend up the sides. Otherwise a pregnant office of your solid will 'run through' the filter paper. Moisten the filter paper with the solvent that makes up the solution, and make certain that information technology adheres well to the bottom. Start up the vacuum and then slowly pour the solution into the funnel.

5. When y'all place a funnel on top of the filter flask, apply a neoprene adapter (the blackness or greyness 'rubbery affair') or rubber stopper to obtain a good seal.

half dozen. When you lot done with the filtration, remove the tubing from the filter flask earlier you turn off the vacuum. It is less of import when you apply a house vac line like in the education lab, only it will when you use an aspirator (the thing using water). The low pressure in the filter flask sucks back the water into the mother liquor, and if this is the part that you are interested, you are back to foursquare one.

7. A vacuum filtration is often non suitable for solvents with low humid points i.e. diethyl ether, dichloromethane or boiling solvents. The solvent evaporates in the vacuum and dissolved solids precipitate, clogging up the pores of the filter paper.

8. If yous accept a very fine precipitate, it is advisable to employ some filter assist similar diatomaceous globe or Celite. This volition prevent that the holes of the filter paper volition get clogged up too fast. This technique is plain not very useful if you are interested in the solid part, because it will exist very time consuming to separate the the product from the filter aid.

Can You Put Too Much Suction On A Filter Flask,

Source: https://www.chem.ucla.edu/~bacher/General/30BL/tips/vacuum.html

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