Publication No. 255.01
The Pink Catalyst
Add a pink cobalt chloride solution to a colorless solution containing potassium sodium tartrate and hydrogen peroxide and
watch as a very obvious green-colored complex forms. As the reaction ends, the solution will return to its original pink color—
indicating that the cobalt chloride catalyst is not used up in the reaction.
Cobalt chloride solution, CoCl2, 0.1 M, 15 mL
Graduated cylinder, 100-mL
Hydrogen peroxide solution, 6%, H2O2, 40 mL
Potassium sodium tartrate solution, 0.2 M, 100 mL
Spatula or scoop
Water, distilled, approximately 100 mL
Stirring rod or magnetic stirrer
Beaker, 500-mL or 1-L
Cobalt chloride solution is moderately toxic by ingestion; the solid is a possible carcinogen as a fume or dust. Hydrogen
peroxide is a strong oxidizer and a skin and eye irritant. Avoid contact of all chemicals with eyes and skin. Wear chemical
splash goggles, chemical-resistant gloves, and a chemical-resistant apron. Please review current Material Safety Data Sheets
for additional safety, handling, and disposal information.
Prepare 0.2 M potassium sodium tartrate solution by dissolving 6 g of KNaC4H4O64H2O in 100 mL of distilled water.
1. Using a graduated cylinder, measure out 100 mL of 0.2 M potassium sodium tartrate solution and pour it into a 500-mL or
2. Place the beaker on a hot plate at a medium setting and slowly warm the solution to 70 °C.
3. When the temperature of the potassium sodium tartrate solution reaches 70 °C, carefully add 40 mL of 6% hydrogen per-
oxide. No reaction is observed.
4. Note the initial pink color of the cobalt chloride solution, and then add the solution to the 500-mL beaker and stir.
5. Observe the rate and progress of the resulting chemical reaction. (The solution turns bright green and vigorous bubbling
ensues within one minute. The mixture begins to froth and foam, t