dilution
When dilution is usually refers to the process of diluting, but also the diluted solution itself. In the process of diluting a is a solvent for the solution of a substance, usually with a known concentration (stock solution) was added. The volume of the solution increases, the concentrations of the dissolved substances decrease. If a highly concentrated solution or even a liquid pure substance (e.g. concentrated sulfuric acid ) is diluted, one must reckon with very strong heat generation.
When stretching a (unauthorized) dilution is an (expensive) luxury food or food or intoxicant called, for example, extended wine , stretched spice or stretched cocaine to the supply or revenue to increase. In the case of such adulterations (see also food adulteration ), the cheap diluent is sold at the expensive price of the goods and thus a higher profit is achieved. In times of need and need, bread flour was also stretched with sawdust or other substances (seeHunger bread ).
principle
Not only the process of dilution, but also the result, the diluted solution itself, can be called dilution (in pharmacy, abbreviated dil. From dilutus (Latin)). The solvent added when diluting is referred to as a diluent when working in the laboratory . B. in the painting trade in the case of paints and varnishes also briefly called thinner . In the kitchen, too, the term dilution is occasionally used incorrectly in the sense of liquefaction and as a contrast to thickening . B. when heated, the viscosity is reduced without increasing the volume. A dilution can not only be achieved by adding liquids , but also by all measures that increase the volume of the solution and lower the concentration of the dissolved substances. A dilution can also be achieved by lowering the concentration of dissolved substances by increasing the temperature or by adding solid or gel-forming substances that dissolve with an increase in volume, even if the viscosity increases (thickening).
Multiple dilutions, i.e. H. Several differently diluted solutions of the starting solution are referred to as a dilution series. The solutions of the dilution series are produced with increasing volumes of the diluent, with the desired end volumes being specified by means of measuring flasks calibrated for the inlet (or sprue) .
Different dilutions
- Dilutions of pathogens , antigens, or antibodies are sometimes referred to as titers .
- The separation of replicable particles such as cells or viruses is used, among other things, in limiting dilution cloning , while a smear is sometimes used for microorganisms .
- The process of restoring thickened fruit juices or freeze-dried samples to their original concentration is known as redilution .
Calculations
When a solution is diluted with a diluent that does not contain the solute, the amount of substance n of the solute remains constant.
- Therefore: . This becomes with
If the index 1 designates the initial state and the index 2 the final state, the concentration of the diluted solution is calculated
A dilution of 1: 100 (1 ad 100) means that 1 ml of a solution with solvent in a 100 ml volumetric flask is made up to a final volume of 100 ml. (The Latin prefix “ad” 'zu' in front of the volume denotes the final volume of the dilution.) The final concentration drops to a hundredth of the initial concentration.
If the diluent also contains the substance to be diluted in a known concentration, the so-called mixing cross must be used to calculate the final concentration .
Tangible examples of dilutions
| dilution | This corresponds to about one drop of alcohol (80 µl ) | |||
|---|---|---|---|---|
| 1: 100 | 10 −2 | 8 ml | half a tablespoon | |
| 1: 1000 | 10 −3 | 8 cl | four shot glasses | |
| 1: 1 million | 10 −6 | ppm | 80 l | a small garbage can |
| 1: 1 billion | 10 −9 | ppb | 80 m 3 | a tank car of the DB |
| 1: 1 trillion | 10 −12 | ppt | 80,000 m 3 | 32 Olympic swimming pools (50 × 25 × 2 m ) |
| 1: 1 billiards | 10 -15 | ppq | 80 million m 3 | a water cube with the edge length of the height of the Empire State Building (449 m) |
| 1: 100 trillion | 10 −23 | 8 million km 3 | twice the content of the Mediterranean (4.3 million km 3 ) or one alcohol molecule in half a tablespoon |
|
literature
- Gerhart Jander , KF year: dimensional analysis. Theory and practice of titrations with chemical and physical indications. 15th edition, Walter de Gruyter, Berlin 1989, ISBN 978-3110119756 .
- AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 .
Web links
Individual evidence
- ↑ Cefic: Measuring low concentrations (PDF; 477 kB)