Barking dog reaction

Barking dog or the barking dog is the colloquial name for a known chemical reaction, which is presented for demonstration purposes in chemistry classes as well in display lectures and similar events because of their visual and acoustic effects and goes back to living in 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 consequently Liebig himself and the Queen Therese and her son were slightly injured Luitpold of Bavaria.

To carry out a mixture of carbon disulfide vapor and the gas nitric oxide is placed in a vertical glass or metal cylinder and ignited at the upper end of the cylinder through an open flame. It burns in a row with rapidly proceeding down flame and an intense bright blue lights, which is one of the few examples of chemiluminescence in a gas phase. Reaction products of the exothermic reaction produces carbon dioxide, sulfur dioxide and nitrogen and, optionally, 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, it comes through the deflagration ( explosion ) as a function of height and diameter of the cylinder in a characteristic sound that resembles the barking or howling of a dog and the reaction gave its name.

The combustion of the aerosol or vapor alcohols such as methanol or ethanol in a similar tube leads to comparable optical and acoustic effects. As the oxidizer can be mixed with a higher reaction intensity, and the non-toxic nitrous oxide and oxygen may be used instead of nitric oxide. The reaction is similar to the detonating gas sample, which is also frequently demonstrated in the chemistry classroom.