When Chemists Attack

Let’s say you don’t want to do the thermite reaction, but you still want to see some very neat looking violent chemistry. The reaction between aluminum and bromine might fit the bill.

2Al(s) + 3Br₂(l) –> 2AlBr₃(s)

It’s a very simple reaction, but it’s also very exothermic, and can put on an impressive show. Not only is enough heat generated to melt the aluminum metal, but the heat also vaporizes some bromine, producing huge clouds of white and orange smoke. For obvious reasons, this reaction should be done where you’ve got very good ventilation. I used my hood for these pictures and this video.

Here’s a still image of the reaction vessel containing only liquid bromine.

Liquid bromine and its vapor.

Bromine is the dark red liquid at the bottom. Bromine is quite volatile, and you can see orange bromine vapor in the top of the beaker.

About ten seconds after adding some torn aluminum foil, things look more like this.

Reaction!

A little later …

Things begin to heat up! (Click to enlarge)

Oh yeah!

Now we’re cooking! (Click to enlarge)

Want to see the video? Here are a few links to a 30-second video file with audio:

• AVI file, uses MPEG4 video and MP3 audio, 805K: This file plays fine under Linux using mplayer or xine. You Windows folks may have trouble with it without installing extra codecs.
• WMV file, 889K: Plays even on my stock school-issue Windows XP machine with Media Player

The aftermath of the reaction is interesting. Some of the aluminum foil melted and fused with the bottom of the beaker.

Aluminum fused to the beaker

Needless to say, we won’t be using this beaker again.

You can see the aluminum bromide product on the sides of the beaker.

Aluminum bromide (white / yellowish solid) on the beaker

The aluminum bromide formed will react with water, causing the release of hydrogen bromide (very nasty to breathe – acidic vapor), so you need to be careful disposing of the product! That reaction is also very exothermic, so touching the product or adding water to it is not recommended. Leave it out long enough, though, and it will absorb water from the air on its own.

Ain’t science neat?

Disclaimer: Do not try this reaction at home. In fact, do not try this reaction at all! You were warned.

Updated with more pictures and video: 04/25/2006

This entry was posted on Monday, April 24th, 2006 at 8:16 pm and is filed under Science, Science education. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.