Oscillating Chemical Reaction (Briggs - Raucher)

(Ref. Chemical Demonstration, B. Shakhashiri)

 

Briggs-Raucher Reaction

 

        1 liter tall form beaker cont. 600 ml 15% hydrogen peroxide

        1 L TF beaker containing 600 ml solution "A"

        1 L TF beaker containing 600 ml solution "C"

        white background board

        magnetic stirring machine and large stir bar

 

Variation (ref. from article given to me by Prof. W. Jolly )

 

Solution A:  0.20M KIO3, 0.080M H2SO4

 

To ~2 liters water add 85 grams potassium iodate, dissolve completely - this can take an hour or more)

add 9 ml 18M H2SO4 (do not add until KIO3 is completely dissolved)

add water to total volume 2 liters

 

Solution C: 0.030% starch, 0.150M malonic acid, 0.020M MnSO4

 

To ~1.5 liters water add 31.2 g malonic acid, dissolve completely

add 6.8 g manganese (II) sulfate.hydrate, dissolve completely

boil ~300 ml water; make a thick paste of water and 0.6 g starch and stir with a glass rod; make the paste thin by adding more water, then add that to the boiling water; boil for a few minutes then let cool; when cool, add to the 3 liters of sol. C, then

add water to total volume 2 liters

 

Solution B: 15% H2O2

 

Make fresh before use (good for a few hours)

Dilute 30% H2O2 by adding equal amount of water

(or use 180 ml 50% H2O2 - for TV 600 ml)

 

Demo: simultaneously pour A and C into B. Works with or without magnet stirring machine. More uniform and consistent w/stirring. Reacts for about 3-5 minutes.