Nutsche
A suction filter (also Büchner funnel , after its inventor Ernst Büchner ) is a filter for the mechanical separation of a suspension . It is used in the chemical laboratory together with a suction bottle for suction or vacuum filtration of solids. For this purpose - similar to the coffee filter - a filter paper is inserted, which can be removed after filtration with the solid.
In modern laboratories, nutsches are increasingly being replaced by (glass filter) frits , which do not filter through an insert made of filter paper, but through a bottom made of sintered glass. Very small particles can be filtered out of a suspension with frits, they are also used in small-scale production.
Standard version
In contrast to a funnel, the nutsche has a cylindrical shape and a flat bottom with small openings (incorporated sieve plate), which are covered by a filter paper. The suspension is poured into the suction filter on the (moistened) filter paper and leaves the solid as a filter cake on the filter paper; the liquid, called the filtrate, is sucked into the suction bottle under the suction filter. The negative pressure required for this is usually generated with the help of a membrane pump or a water jet pump that is connected to the suction bottle via a vacuum hose.
Nutsches have little stability due to the small footprint, a high center of gravity and the bulkiness of the vacuum hoses used and must therefore be fixed to a stand rod with a stand clamp and a stand sleeve for safety reasons .
Special designs
Another suction technology is pressure suction, in which - instead of suction from below - an overpressure is generated from above with a gas supply .
Certain types of nutsches can also be heated so that the dissolved substance does not precipitate. This method is mostly used for clear filtration of solutions . Nutsches can also be frozen (down to −78 ° C with dry ice ) in order to avoid decomposition of the analyte .
Nutsches with an agitator are also used in large-scale production . They are mainly used when the product has to be washed. By stirring, a greater contact between product particles and washing liquid can be achieved, which makes washing a lot more economical.
Individual evidence
- ↑ Heinz GO Becker, Werner Berger, Günter Domschke, Egon Fanghänel , Jürgen Faust, Mechthild Fischer, Fritjof Gentz, Karl Gewald , Reiner Gluch, Roland Mayer , Klaus Müller, Dietrich Pavel, Hermann Schmidt, Karl Schollberg, Klaus Schwetlick, Erika Seiler and Günter Zeppenfeld: Organikum , Johann Ambrosius Barth Verlag, 1993, 19th edition, pp. 30–32, ISBN 3-335-00343-8 .