Chlorine & Aluminum reaction demo: hints on what are the critical parameters?

I'm a laboratory technician from Quebec - Canada and for many years, I have tried to perform the demonstration detailed by the Nuffield Foundation & Royal Society Chemistry for the reaction of generated Chlorine with Aluminum foil:
https://edu.rsc.org/experiments/rea...nd iodine.&text=2Al + 3X2 → 2AlX,Cl, Br and I).

The results varied so much, from good reaction to slow reaction, to even no reaction at all besides some fumes... I cannot point out to what are the critical parameters to make this demonstration a repeatable success!

any hints?
 
The chlorine gas is generated, yes, in the vessel. I had to boost the hypochlorithe and use concentrated acid to have a good chlorine content. But most of the time, when I heat the reaction tube, I have a lot of white fumes... then sometimes a few sparks of bright blue light, but that dies really quickly. I have tried to ''dry'' the Al foil with alcool before, just to try preventing a moisture to kill the reaction, but it does't help much. I wonder if the quality of the aluminum foil is important???
 
The chlorine gas is generated, yes, in the vessel. I had to boost the hypochlorithe and use concentrated acid to have a good chlorine content. But most of the time, when I heat the reaction tube, I have a lot of white fumes... then sometimes a few sparks of bright blue light, but that dies really quickly. I have tried to ''dry'' the Al foil with alcool before, just to try preventing a moisture to kill the reaction, but it does't help much. I wonder if the quality of the aluminum foil is important???
Okay try Conc HCl and potassium permanganate VII in your chlorine generator.

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So, 5 g of KMNO4 and excess volume of HCl 12N ? Did you ever get a fast & strong reaction with this? Would it be better to use aluminum powder instead of foil??
 
Hi all - for those who are attempting these demos:
1) Br2 works without a problem and is really interesting - you can watch the reaction to Iodine, except the vapors are brown compared to deep purple with Iodine. However, getting Br2 is costly... worth it still, I think.

2) for Cl2 reaction, the trick is to get a head start and a good concentration of gas. so:
- Chlorine production:
- use small glassware (eg 18 tube for reduction zone, 50mL erlenmayer for generator);
- use calcium hyppochlorite (10 g solid, from pool supply)
- scrape gently the aluminum foil with emery paper;
- preheat the foil in the reduction vessel BEFORE you start the Cl2 production; add 5-6 M HCl to the CaOCl in 2-3 shots of 3mL (this will gently push the gas into the vessel as you add another aliquote)
- continue to heat the vessel for few seconds until the reaction starts, then stop the gas. The Al will be consumed in few seconds.
- if you want to continue with adding water to the reduction vessel to show the AlCl3 presence & acidity, be aware that local exothermic reaction of AlCL3 with water may shatter the test tube :)

With these conditions, I was able to repeat this demonstration easily and reliably. And please, use the fume hood...

Have fun !
 
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