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Has anyone seen a version of the iodine clock reaction where instead of the system oscillating between clear and blue it shows blue bands travelling down the vessel?

I ask because someone not unknown to this site has made a version of the experiment with such moving bands and I was wondering if it was worth sending a write up of it to the Journal of Chemical Education or some similar journal.

Clarification:

Apologies if I was unclear, I am asking the phenomenon has been published before or if it is unpublished but already well known.

I know the BZ reaction can produce all sorts of patterns, but I have never seen travelling bands in the iodine clock. A quick Google has found no mention of the phenomenon. I am not asking "is it worth publishing", which I believe is against site rules anyway. I'm just asking about prior art.

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  • $\begingroup$ Uhhh... I'm not sure what you're saying or what your question is, exactly. Did you get that reaction to run and would like to know if it's worth writing a paper on it? Did you see it and would like to do a writeup for the researcher who got the reaction to work like that? Did you hear someone did it and would like to write a paper without even having seen it yet? Or something else entirely? Also, who's "someone not unknown to this site"? :) $\endgroup$ – Tanith Rosenbaum Apr 9 '13 at 21:18
  • $\begingroup$ @TanithRosenbaum: He means me ;-) I basically had modified the Briggs–Rauscher oscillatory reaction for fun, and it resulted in cascading bands in a beaker. John suggested I publish it in JCE; I was skeptical that it was big enough to be published. $\endgroup$ – ManishEarth Apr 10 '13 at 1:41
  • $\begingroup$ @ManishEarth: actually, now I think about it, if all you did was add layers of the reagents prepared at successively later times this isn't very interesting. I was assuming the horizontal banding arose spontaneously or at least without excessive manual manipulation. $\endgroup$ – John Rennie Apr 10 '13 at 12:16
  • $\begingroup$ @JohnRennie: Well, it wasn't excessive manual manipulation. I let the normal reaction take place fully. Whatever was left, I poured some selected reactants on in a certain order (quickly, but carefully). That was all the manipulating involved, the bands happened automatically. There is no manipulation during the entire duration of the video :) $\endgroup$ – ManishEarth Apr 10 '13 at 12:20
  • $\begingroup$ @ManishEarth: well if you can reproduce it I reckon chemistry teachers across the world would like the recipe :-) $\endgroup$ – John Rennie Apr 10 '13 at 14:48
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Whilst not specifically an iodine clock reaction, Belousov-Zhabotinski reactions are oscillatory and can produce moving bands, spirals and concentric circles of colour. This works best in thin films (limiting convection) as the top commenter on the linked video points out.

There's a great thesis by Peter Hantz which looks at these kinds of reactions in detail (the first bit is in french, the rest is in english) and specifically covers Liesegang banding, where an oscillating chemical reaction in a mobile phase causes bands of precipitation in a gel column. As Hantz points out on page 22, the gel is required to prevent convection from destroying the bands, however the viscosity of the gel also freezes the precipitate in place as it forms. This would seem to be close to what you are interested in, however.

Here's a picture of Liesegang bands in test tubes from wikipedia:

enter image description here

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  • $\begingroup$ Ah, but the Belousov-Zhabotinski are supposed to be hard to get right (not something you'd do in a first year undergrad lab). Any idea if a modified version of the Briggs-Rauscher that creates cascading bands has been published before? If not, is it worth publishing in an educational journal like the JCE? (it's something quite easy to do in the lab, and quite fun once you get it. Plus you can try to make it faster.) $\endgroup$ – ManishEarth Apr 10 '13 at 1:45
  • $\begingroup$ @ManishEarth - I'm not sure. If it's a novel reaction I would say it's worth publishing or at the very least blogging. I was thinking that a Briggs-Rauscher reaction in viscous media (for instance, K-Y Jelly) or a beaker full of polyacrylamide water beads with reagents injected at different points might produce some neat effects. $\endgroup$ – Richard Terrett Apr 10 '13 at 1:59
  • $\begingroup$ I didn't use any special media, just the normal reagents (not a novel reaction per se, it's just the process of mixing the reagents). But yeah, sounds like something nice to try :) Not sure if it would make any difference, though -- there's nothing moving in the oscillatory reaction, you just have the impression of motion (like Christmas lights). Then again, I can see how it may make a difference in the initial stages. $\endgroup$ – ManishEarth Apr 10 '13 at 2:02
  • $\begingroup$ @ManishEarth - I understand that, but playing with viscosity and percolation may provide new opportunities for messing with the phase of the oscillation as a function of position as well as creating concentration gradients of reactants, which should affect the rate of oscillation as a function of position. $\endgroup$ – Richard Terrett Apr 10 '13 at 2:06
  • $\begingroup$ Ah, right, didn't think of that. Good insight! :) $\endgroup$ – ManishEarth Apr 10 '13 at 2:08

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