Oscillating reaction -- cool experiment

[woelen]

I finally could do an oscillating reaction at home. It is really cool to see this happen. The chems, needed for this experiment are quite easy to get your hands on, or you simply make them. Most notably the needed KBrO3, I made this myself, another page on that will follow soon, a solution, containing Mn(2+) ions also is not that hard to make if you don't have manganese (II) salts.

 

http://woelen.scheikunde.net/science/chem/exps/oscillating/index.html

 

The only chemical, which is harder to obtain and quite expensive is malonic acid, HOOC-CH2-COOH. Citric acid can be substituted for this, but the effect by far is not so nice with citric acid.

[psynapse]

So what is an oscillating reaction? What do you observe?

[Darkblade48]

So what is an oscillating reaction? What do you observe?

In general, oscillating reactions will show some colour change (be it red to blue, yellow to purple, colourless to coloured, etc) that will oscillate (go back and forth) between the colours.

 

Very neat experiment Woelen! Can't wait to see the page on making KBrO3

[YT2095]

Nice

 

I can`t be 100% sure, but Oxalic acid should make a beter replacement than Citric acid, is breaks down to CO2 quite readily. Might be worth a try

[woelen]

Unfortunately, oxalic acid doesn't work. If you look at the reaction mechanism for oscillating reactions, then you that that you need a specific pathway for the oxidation of the organic compound. Oxalic acid is oxidized straight away, you simply get CO2 and bromide (or bromine if KBrO3 is in excess) and that's all. I also tried ascorbic acid, and that gives a similar non-interesting result. Up to now, I only found malonic acid and citric acid as useful reagents for the oscillating reaction, and citric acid only does so in a limited way. You get loads of turbid crap in the liquid and it makes the reaction much less attractive.

[YT2095]

ok dokes, cheers for that

 

I`ve got a Bromate cell on the go right now, so I`ll give that go in a few days time