Embudo Büchner

November 2, 2021

Filtration is a process carried out in laboratories to separate solids from liquids, in this process the Büchner funnel is used, an equipment used in vacuum filtration or pressure-assisted filtration.

What is it?

A Büchner funnel is laboratory equipment used to perform pressure-assisted or vacuum filtration. The most traditional are made of porcelain, but can be found in glass and plastic, the latter are used in secondary schools.

Its design is attributed to the industrial chemist, Ernst Büchner.

How is it used?

In the funnel-shaped part there is a cylinder separated by a perforated porcelain plate with small holes. The filter material (often filter paper) is cut out in a circular shape and placed on the plate. It is important to emphasize that the filter paper must be trimmed properly to ensure that it covers the holes in the porcelain, but should not be raised on the side walls. To avoid this, the paper is moistened with distilled water to fix it to the base.

The liquid being filtered is placed inside the cylinder. Once the entire system is armed, the liquid is sucked through the plate and the filter paper by a vacuum pump that creates a Venturi effect, using a kitasato and a stream of water. The funnel has a rubber ring or gasket that will fit perfectly with the mouth of a kitasato.

The vacuum generated in the flask has a value such that a pressure of 15 lb / in 2 is exerted on the liquid when it is filtered, which pushes it towards the kitasate.

If the liquid to be filtered it is important to place a trap between the kitasato and the water or suction tube to prevent the water from returning and contaminating the filtered liquid.

Previously, asbestos sheets were used instead of filter paper. The moistened asbestos was placed on the perforated bale and then calcined to leave a hard asbestos plate as a filter element. This is why Büchner funnels are made of ceramic. Filter paper creates poor filtration.

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.
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