Frit (filter)
The frit is a filter made of glass or ceramic that is used to filter even the finest particles. The glass or ceramic is porous, so that the substance to be filtered out remains in the pores like a very fine sieve .
Manufacture and name
Frits consist of a funnel into which a filter is incorporated. The filter is made of porous glass with various pore openings. This glass material is obtained by caking together glass powder below the melting point (and possibly quenching in water). Such powder or glass cake was previously called frit and was only stored for further glass production.
use
The use of the frit depends on the size of its pores. According to ISO standard 4793, a distinction is made between seven pore sizes according to the respective filtration purpose:
| ISO marking | Labelling | Nominal size of the pores in µm |
Area of application of the frit |
|---|---|---|---|
| P 500 | POR 00 / G 00 | 250-500 | Filtration of coarse precipitates, gas distribution in liquids with low gas pressure |
| P 250 | POR 0 / G 0 | 160-250 | Filtration of coarse precipitates, gas distribution in liquids with low gas pressure |
| P 160 | POR 1 / G 1 | 100-160 | Coarse filtration, gas distribution with higher pressure |
| P 100 | POR 2 / G 2 | 40-100 | Preparative fine filtration, preparative work with crystalline precipitates, diffusion of gases in liquids |
| P 40 | POR 3 / G 3 | 16- 40 | Analytical filtration, analytical work with medium-fine precipitates, preparative work with fine precipitates, diffusion of gases in liquids |
| P 16 | POR 4 / G 4 | 10- 16 | Analytical fine filtration, analytical and preparative work with very fine precipitates, very fine gas distribution in liquids by means of pressure, shut-off valves for mercury |
| P 1.6 | POR 5 / G 5 | 1- 1.6 | Fine filtration, bacteriological filters, filtration of larger microorganisms, extremely fine gas distribution in liquids by means of high pressure |
cleaning
If frits are blocked with fine particles due to careless work, discolored or simply no longer run well, one often uses strong oxidizing agents to remove the impurities. Caro's acid , freshly prepared from sulfuric acid and commercially available hydrogen peroxide, is used for this. The high reactivity of this oxidizing agent with organic substances and the potentially explosive decomposition in the presence of suitable catalysts must be taken into account. Alternatively, suitable frits can also simply be annealed in many cases.
Inlet frit
At the end of the hose with which liquid is sucked in from a storage vessel - e.g. B. for chromatography - i. d. Usually similar porous bodies are attached and referred to as inlet frits. They often have the shape of a cylinder (height greater than diameter) with a connector for the hose attached at the top. In contrast to normal (filter) frits, they are often made of metal.
See also
- Frit (material)
- Sintering - supplies porous metal components, which are sometimes also called frits
- Coherers , also known as fritters, contain loose iron filings as their main component