A mixture of three solutions periodically changes color and glows in UV
name: Fluorescent oscillating reaction with ruthenium and cerium ions
fluorescent Briggs Rauscher Reaction
Fluorescent Oscillating Reaction Demonstration Kit - Flinn Scientific
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Br2 + CH2(COOH)2 → BrCH(COOH)2 + Br- + H+
BrO3- + 12H+ + 10 Ce3+ → Br2 + 6H2O + 10Ce4+
Ce4+ + Ru2+ → Ce3+ + Ru3+
- Mix 16 g of malonic acid, 0.30 g of potassium bromide and 300 ml of water. It is solution A.
- Mix 13 g of potassium bromate and 300 ml of water. It is solution B.
- Mix 0.045 g of tris(bipyridine)ruthenium(II) chloride hexahydrate, 0.38 g of cerium(IV) nitrate and 150 ml of 6M sulfuric acid. It is solution C.
- Put a magnetic stir bar and pour solutions A and B into a 1l beaker, place the beaker on a magnetic stirrer and start to stir.
- Pour solution C into the beaker.
- Carefully lower a UV lamp into the beaker and secure it so that the liquid does not contact with the socket of the lamp.
- Make it dark and switch on the UV lamp. There are oscillations between bright and dark fluorescent orange in the solution.
This reaction is a modification of the Belousov-Zhabotinsky (BZ) reaction, and has the same mechanism. But there is an important additional reaction in this modification - the Ce4+ ions react with the Ru2+ ions producing the Ce3+ and the Ru3+ ions. The Ru3+ ions fluoresce in UV whereas the Ru2+ ions don't.