Question: What exactly is the "Barking Dog" reaction?

Andrew McKinley answered on 23 Jun 2010:

It’s an amazing reaction – try looking on youtube to see (and hear!) the demonstration in progress.
Basically, you have a glass tube with a mix of Carbon disulfide (CS2) and and nitrogen monoxide (NO). You hold the tube vertically, and ignite the tube at the top. A bright blue flare travels slowly down the tube, and when it reaches near the bottom, the correct combination of oxygen, CS2 and NO makes an explosive mixture that goes *WOOF!* with a blue flash up the tube. The ‘woof’ sounds like a dog barking, hence the name.

In the late 1800’s/early 1900/s it was used as a light source for photographs indoors as the blue light is so intense – obviously the fact that it is blue doesn’t affect the black-and-white photograph!

Seriously – look it up on youtube, it is an amazing reaction. Better still, if you can persuade your chemistry teacher to show it to you – and something that is important – leave a bit of water in the bottom of the glass tube to cushion it from the explosion – you don’t want glass going everywhere!