Liesegang rings
As Liesegang rings refers certain periodically occurring structures in chemical reactions ( reaction-diffusion systems ). For example, when silver nitrate solution is dripped onto a chromate-containing gel, red, concentric ring-shaped precipitation zones of sparingly soluble silver chromate form at certain distances from the dripping point . This phenomenon was described by Raphael Liesegang (1869–1947) in 1896 and later named after him. In addition to Liesegang, the chemist and Nobel Prize laureate Wilhelm Ostwald (1853–1932) carried out research in this area.
Liesegang rings also occur in porous and clastic rocks ( sandstone ). The structures, which are clearly visible in the cut, arise during weathering through diffusion of solutions into the rock with reprecipitation in deeper areas. Brown color usually indicates iron-containing compounds in the penetrated water. The structures are formed concentrically inwards, approximately parallel to the rock surface, but increasingly follow pre-marked cracks and fissures . The so-called " landscape stones ", which were created according to this principle, are known as decorative objects or elegant wall cladding .
Liesegang rings produced experimentally
Liesegang rings on the cliffs of Pénestin in Brittany
Liesegang rings in a sandstone with a scale ( geologist's hammer )
See also
Web links
- Seilnacht: illustrations and experiments
- Dr. Blume: Periodic reactions in gels: Liesegang's rings
Individual evidence
- ↑ Raphael Ed. Liesegang - About some properties of jellies (1896)
- ^ Friedrich R. Kreissl, Otto Krätz: Fire and Flame, Sound and Smoke: Show experiments and chemical history . 2008, ISBN 978-3-527-32276-3 , pp. 187 ( limited preview in Google Book search).
- ↑ Helmut Schrätze: The emergence of endogenous ore deposits . 1986, ISBN 3-11-009749-4 , pp. 74 ( limited preview in Google Book search).
- ^ Landscape marble