Chemical garden
A chemical garden is a show experiment in which various colored heavy metal salts are added to an aqueous solution of sodium silicate .
The ions of the heavy metals react at the interface to form sparingly soluble, colored silicates . If you use large crystals of the heavy metal salts, sometimes bizarre structures with a fractal appearance result. The shape results from the fact that the interface between the heavy metal salt or its concentrated solution and the water glass acts as a semipermeable membrane (precipitation membrane ) and water can flow in through osmosis . As a result, the membrane expands and may burst. Since the salt density is lowest at the top of the structure, it mainly grows upwards. Branches to the sides also take place, so that a plant-like structure results.
Salts that can be used are e.g. B.
- Alum (potassium aluminum sulfate) - white
- Copper sulfate - blue
- Chromium (III) chloride - green
- Nickel sulfate - green
- Iron (II) sulfate - green
- Iron (III) chloride - orange brown
- Cobalt chloride - purple
literature
- Julyan HE Cartwright, Juan Manuel García-Ruiz, María Luisa Novella, Fermín Otálora: Formation of Chemical Gardens. In: J. Colloid Interface Sci . 256. 2002, 351-359. (online) ( Memento from July 21, 2012 in the Internet Archive )