Calcination
As calcination , calcination or calcination (from Latin. Calx for limestone ) is referred to in the chemical heating ( firing ) of calcium and magnesiumcarbonathaltigen minerals with the aim to drain these or decompose.
The calcination takes place during lime burning , as part of the technical lime cycle . The decomposition products formed are water, calcium oxide (or other metal oxides) and the escaping carbon dioxide (CO 2 ). The calcination processes take place in a similar way with magnesite and dolomite .
The process also takes place in the production of gypsum and basically in the removal of crystal water from hydrated salts (example: calcined soda ). When firing clay and porcelain, bound water also escapes while the particles sinter together .
Technically, calcination plays z. B. in the production of cement , aluminum oxide or the processing of petroleum coke (see Delayed Coking ) a role. Rotary kilns are mainly used for this. Calcium oxide (quicklime) is mainly produced in shaft furnaces .
Calcination is used in the analysis of glass fiber reinforced plastics in accordance with DIN EN ISO 1172 to determine the textile glass and mineral filler content. This method is a thermogravimetric analysis after incineration .
history
In alchemy , calcination played an important role. The term “calcinatio” broadly denotes the pulverization of a substance, often by roasting it in a bowl. Under calcination or calcination is understood in the Spagyrik the incineration of dried medicinal herbs.
Calcium oxide was extracted as a building material through calcination as early as Roman antiquity . For example, corresponding ovens were found along the Limes .
In the 18th century, calcination was understood to be the heating of solids over a fire and the associated “expulsion of volatile substances”. Before the discovery of oxygen , it was not understood that the “calcination” of metals and the “calcination” of lime were completely different reactions. In the first case, oxygen from the air is combined with the metal, which leads to an increase in weight. In the second case, carbon dioxide is split off, which reduces the weight of the solid. The increase in weight in the case of calcination of metals was wrongly explained by the existence of a hypothetical substance from the fire (" phlogiston ").
See also
Individual evidence
- ↑ Der Brockhaus, Science and Technology , FA Brockhaus, Mannheim; Spectrum Academic Publishing House, Heidelberg, 2003.
- ↑ Entry on ceramics. In: Römpp Online . Georg Thieme Verlag, accessed on May 25, 2014.
- ↑ Entry on calcining. In: Römpp Online . Georg Thieme Verlag, accessed April 10, 2011.
- ↑ Claus Priesner, Karin Figala (Ed.): Alchemie - Lexicon of a hermetic science , CH Beck, Munich, 1998, p. 53.
- ^ Samuel Hahnemann: Apothekerlexicon, Leipzig 1793, p. 460. online at google books