Büchner funnel

November 1, 2021

The Büchner funnel is a funnel specially designed for filtration . Funnels are instruments that are used to transfer liquids from one container to another, their use dates back to the Middle Ages, when this tool was used. It is made up of a hollow body, with two ends of different lengths, one being wider than the other.

Filtration is the process of separating a solid agent from a liquid through its suspension. The need to attach the filtration as a function of the funnel arises when a substance is required to be transferred, which in turn is mixed with some solid. So, to streamline the process, both functions are performed in just one action.

What is the Büchner Funnel?

The Büchner funnel has the particularity of not only being a filtering funnel, but specifically a vacuum or pressure filtering funnel . Vacuum filtration separates the solid-liquid mixture, just like regular filtration, but its way of doing it is somewhat different, since the vacuum sucks the liquid.

This system works with the Bernoulli principle, which establishes that in an ideal fluid the pressure decreases as the flow speed increases, producing the venturi effect, in which, if the conduit where the liquid flows is connected to another, an aspiration of the fluid occurs. from one conduit to the other.

This funnel was designed by industrial chemist Ernest Büchner in 1888 and is made of porcelain. Many laboratory instruments are made of this material, because thanks to its properties, such as its resistance to corrosive chemicals, high temperatures and almost zero porosity, it is ideal for dealing with most compounds.

Its design is the same as any funnel , with a wide and a narrow part, although in this one it is a little shorter than in traditional funnels. The difference that distinguishes it is the plate with perforations in the wide end of the funnel, to perform the filtration.

What is the Büchner Funnel for?

There are two ways to perform filtration, gravity filtration and vacuum filtration . Gravity filtration is done through filtration funnels and is used for cases in which it is required to filter solid impurities, drying agents and, in general, any process for the disposal of the solid and conservation of the solution.

Filtration under vacuum or reduced pressure is much faster than filtration by gravity and it is this that the Büchner funnel takes care of, if in gravity filtration what you want to discard is the solid, in vacuum filtration it is What is being discarded is the liquid, isolating the solid, which is why the absorption that is created in a vacuum is needed.

Uses of the Büchner Funnel

While isolating the solid component is one of the main uses for the Büchner funnel, it is not the only one. Thanks to its rapid filtration process, it is used for substances in other conditions, such as crystals in the crystallization process, in which the atoms of a liquid form bonds to create a crystallization network.

It is also used in solids in the precipitation process , that is, in the process of the formation of the solid from the chemical reaction of a solution. As you can see, the vacuum filtration method is used in substances that are undergoing processes and must be filtered quickly, and for this the Büchner funnel is used.

To use the Büchner funnel it is important to bear in mind that the solid to be separated must not be of very small dimensions, otherwise it could be transferred with the liquid. In any case, the use of filter paper is also used when using the funnel, cut in a circular way to cover the area.

Types of Büchner Funnels

The Büchner funnel itself is a subtype within filtration funnels, which are themselves funnel types, so there are no “types of Büchner funnels”, as such, beyond the differences they may have. one from another, with respect to the material from which they are made, which varies between plastic, porcelain and glass, such as the glass funnel , for example, and / or its dimensions.

Filtration funnels are of various types, in addition to the Büchner as the decanting funnel. Variations can occur at the design level, also with slightly different shapes and different lengths.

Characteristics of the Büchner Funnel

The Büchner funnel is usually found in dimensions of about 15 cm. Made of porcelain or glass; They are a hollow body that, at the base of the wide part, has a porcelain plate with holes. Despite these holes, for its use, a filter paper is used that is placed on the plate.

The Büchner funnel works with a kitasato flask , which is a glass container with a drop tube to create a vacuum. For this reason, this funnel must be used together with the flask in order to generate the necessary pressure to create the venturi effect.

There are several models of funnels that are used with other instruments, more than the entire flask, which is where substances or tweezers are usually dumped to hold. There are also substances or procedures that must be carried out under certain conditions, so it is prudent to take this into account when using the funnel.

Importance of the Büchner Funnel

The funnel is an extremely useful instrument, it is used in many procedures in the laboratory and can never be absent from it. It is next to the flask, one of the most common and used instruments. The Büchner funnel is designed for cases where rapid filtration processes are required and without this it would be cumbersome to apply such procedures.

Funnels are part of a wide range of laboratory instruments, specifically chemical ones. Although there are instruments for all fields, such as electronics or physics that their specialized ones have.

Dr. Loony Davis5
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Born and raised in Brussels in an English family, I have always lived in a multicultural environment. After several work experiences in marketing and communication, I came to Smart Water Magazine, which I describe as the most exciting challenge of my career.
I am a person with great restlessness and curiosity to learn, discover what I do not know, as well as reinvent myself daily, someone who is curious about life and wants to know. I enjoy sharing knowledge.
This is my personal project but I also collaborate in other blogs, it is the case, the most important web on water currently exists in the US, if you are interested you can read my articles here.

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