What are chelators?
A chelator is a molecule of a substance that accumulates around the central atom of another chemical substance. The word chelator derives from the Greek word for cancer away. The name is intended to make it clear that the molecule like the claws of a crab grasping around a central atom. Because of its structure, the chelator occupies several or all of the binding sites. Complex compounds are thus generated which are difficult to break. These connections are also called the pincer complex.
The covered fabric, e.g. B. a metal, does not change itself, but remains so in solution. It is protected both from oxidizing substances and from substances which would otherwise form insoluble substances with the coated metal. Copper thus becomes less toxic when chelated. In the case of heavy metal poisoning, chelators are therefore given intravenously. Detergent softeners work in a similar way, preventing calcium and magnesium from clumping together.
Chelators are used in aquaristics e.g. B. important for iron fertilizers. There they prevent the fertilizers, e.g. As iron, are precipitated in the aquarium water and the aquarium plants are no longer available. A well-known chelator in aquarium fertilizers is called EDTA.
In the correct pH range, EDTA occupies all 6 binding sites with iron. Instead of a complex of an iron cation and 6 water molecules, a complex of iron and an EDTA is formed. This complex is so stable that iron no longer precipitates but remains in solution and is thus available to the plants.
Chelates dissolve very well in water. The iron, together with the chelators, is completely absorbed by the plants. Plants themselves produce various chelators, which they use to harness metals. They excrete an acid through the roots, which dissolves iron in the substrate and makes it usable for the plants.
The resulting complexes are broken down into their components by certain bacteria, so that coated metals can be released again. Heat and strong acids can break the bond or destroy the chelator.
With some water tests for iron, it is therefore recommended to heat the test in order to correctly measure the iron content in the aquarium water. Due to the chelators in the fertilizer, the iron cannot initially be detected by the iron test. The heat breaks the bonds between iron and chelator and the iron becomes detectable.
Water tests for total hardness consist of a chelator solution and an indicator. The indicator reacts to the calcium contained in the water and changes colour. To prevent acid from destroying the chelator, the test contains ammonia and therefore smells like it.