Barking dog

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The barking dog

Barking dog or The barking dog is the colloquial term for a well-known chemical reaction which, due to its optical and acoustic effects, is presented for demonstration purposes in chemistry lessons as well as in show lectures and similar events. It goes back to the 19th century chemist Justus von Liebig . The level of awareness is partly due to the fact that a demonstration by Liebig in front of the Bavarian royal family in April 1853 failed and as a result Liebig himself and Queen Therese and her son Luitpold were slightly injured by Bavaria .

To do this, a mixture of vaporous carbon disulfide and the gas nitrogen monoxide is filled into a vertical glass or metal cylinder and ignited at the upper end of the cylinder by an open flame . It then burns with a flame running rapidly downwards and an intense light blue glow , which is one of the few examples of chemiluminescence in a gas phase . The reaction products of this exothermic reaction are carbon dioxide , sulfur dioxide and nitrogen and possibly, depending on the stoichiometric ratio of the starting materials, small amounts of sulfur , which is visible on the wall of the cylinder due to its yellow color. Furthermore, the deflagration (deflagration), depending on the height and diameter of the cylinder, leads to a characteristic noise that is similar to the barking or yowling of a dog and gave the reaction its name.

The combustion of aerosol or vaporous alcohols such as methanol or ethanol in a similar vessel leads to comparable optical and acoustic effects. The non-toxic dinitrogen monoxide or oxygen can also be used instead of nitrogen monoxide as an oxidizer with a higher reaction intensity . The reaction is similar to the oxyhydrogen sample , which is also often demonstrated in chemistry class.

literature

  • Barking dog. In: Friedrich R. Kreißl, Otto Krätz: Fire and Flame, Sound and Smoke: Show experiments and chemical history. Second edition. ISBN 3-52-732276-0 , Wiley-VCH, Weinheim 2008, pp. 130-132.
  • Barking dog. In: Herbert W. Roesky, Klaus Möckel: Chemical Cabinet Pieces. Spectacular experiments and witty quotes. Wiley-VCH, Weinheim 1994, ISBN 3-52-729220-9 , pp. 228/229.
  • Blue Lightning Through Explosions of Gas Mixtures. In: Hans-Dieter Barke, Günther Harsch, Siegbert Schmid: Essentials of Chemical Education. Springer, 2011, ISBN 3-64-221755-9 . Pp. 54/55.
  • Ché Royce Seabourne, George Maxwell, James Wallace: Taming the Barking Dog. In: Journal of Chemical Education. 83 (5) / 2006. ACS Publications, p. 751, ISSN  0021-9584 .
  • William H. Brock : Justus von Liebig: A biography of the great natural scientist and European. Vieweg, Braunschweig 1999, ISBN 3-52-806995-3 , p. 94.

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