oscillating reaction Briggs-Rauscher

[Karin]

I am looking for a tried and tested method for the BR oscillating reaction. I have tried the method below but it didn't work for me. Any ideas of what could go wrong?

Solution A-1. Pour 400 mL of distilled water into a 2-liter beaker. Wearing gloves, pour 410 mL of
30% hydrogen peroxide into the beaker of water. Dilute the solution to 1.0 liter with distilled water.
This solution is 4.0M in H2O2.
Solution A-2. Place 43 g of potassium iodate and approximately 800 mL of distilled water in the
second 2-liter beaker. Add 4.3 mL concentrated H2SO4 to this mixture. Warm and stir the mixture
until the potassium iodate dissolves. Dilute the solution to 1.0 liter with distilled water. This
solution is 0.20M in KIO3 and 0.077M in H2SO4.
Solution A-3. Dissolve 16 g of malonic acid and 3.4 g of manganese(II) sulfate monohydrate in
approximately 500 mL of distilled water in the third 2-liter beaker. In the 100-mL beaker, heat 50
mL of distilled water to a boil. In the 50-mL beaker, mix 0.3 g of soluble starch with about 5 mL of
distilled water and stir the mixture to form a slurry. Pour the slurry into the boiling water and
continue heating and stirring the mixture until the starch has dissolved (1-2 minutes). The solution
Wet Lab 3 / p.7
may be slightly turbid. Pour this starch solution into the solution of malonic acid and manganese(II)
sulfate. Dilute the mixture to 1.0 liter with distilled water. This solution is 0.15M in malonic acid
and 0.020M in MnSO4.
Pour equal quantities of solution A-1 and solution A-2 into the beaker on the
magnetic stirrer. Adjust the stirring rate to produce a large vortex in the mixture.
Pour an equal quantity of solution A-3 into the beaker. (This will produce a
mixture whose nominal contents are 0.050M malonic acid, 0.0067M Mn2+,
0.067M IO3-, 1.3M H2O2, and 0.038M H2SO4.) The initially colorless solution will
become amber almost immediately. Then, it will suddenly turn blue-black. The
blue-black will fade to colorless, and the cycle will repeat several times with a
period which initially lasts about 15 seconds but gradually lengthens. After a few
minutes, the solution will remain blue-black.

Cheers,
Karin

[kimmy]

This is what we use

I normally only make what is needed depending on class size.


Briggs-Rauscher Oscillating Color Change Reaction
The Briggs-Rauscher reaction, also known as 'the oscillating clock', is one of the most common demonstrations of a chemical oscillator reaction. The reaction begins when three colorless solutions are mixed together. The color of the resulting mixture will oscillate between clear, amber, and deep blue for about 3-5 minutes. The solution ends up as a blue-black mixture.
Materials
• Solution A:
Add 43 g potassium iodate (KIO3) to ~800 mL distilled water. Stir in 4.5 mL sulfuric acid (H2SO4). Continue stirring until the potassium iodate is dissolved. Dilute to 1 L.
• Solution B:
Add 15.6 g malonic acid (HOOCCH2COOH) and 3.4 g manganese sulfate monohydrate (MnSO4 . H2O) to ~800 mL distilled water. Add 4 g of starch. Stir until dissolved. Dilute to 1 L.
• Solution C:
Dilute 400 mL of 30% hydrogen peroxide (H2O2) to 1 L.
You will need:
• 300 mL of each solution
• 1 L beaker
Procedure
1. Pour 300 mL each of solutions A and B into the beaker.
2. Mix well
3. Add 300 mL of solution C into the beaker. Be sure to add solution C after mixing solutions A + B or else the demonstration will not work. Enjoy!

[rosaliemb]

Prof Bunsen has a kit of all chemicals needed for this. "The Facinating Oscillating Reaction kit"
I couldn't locate source of malonic acid.

Rosaliemb(another one)

[Lyn]

ChemSupply has malonic acid.
Lyn.

[RosalieL]

Any current tips for making this one work?

[RosalieL]

Prof bunsen doesn't seem to do the kits anymore. Does anyone know where else to find them in Australia? I have found one in the US but shipping is more than the kit... but 2x class kits plus shipping is still cheaper than a bottle of malonic acid on it's own so possibly worth it (except not knowing how long it will take to show up!).