Barking dog reaction

The "Barking Dog" is an exothermic chemical reaction that results from the ignition of a mixture of carbon disulfide and nitric oxide.

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It has been known for centuries; in 1853, Justus von Liebig was using the bright blue flash and the distinctive ‘woof’ sound of the demonstration to enthrall his students.

In simple terms, the ‘Barking Dog’ reaction is a combustion process, in which a fuel (carbon disulfide, CS₂) reacts with an oxidiser (nitric oxide (NO) or nitrous oxide (N₂O)), producing heat. The flame front in the reaction is a zone of very hot, luminous gas, produced by the reactants decomposing.

This reaction is similar to the well-known hydrogen-oxygen reaction, but is accompanied by a characteristic “barking” sound. A mixture of nitric oxide and the vapour of carbon disulfide, contained in a long tube, is ignited. The combustion wave travels at a moderate rate down the tube compressing the gas ahead of it. At a certain distance, dependent on the diameter of the tube, the residual mixture explodes. In a very long tube the passage of the explosion wave may be seen. This reaction also produces a considerable amount of very bright blue light and is one of the few examples of chemical luminescence in the gas phase.

External links

• University of Leeds Barking Dog site
• Page linking to a recorded lecture on the reaction