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Demonstration of Microscale Projection Experiments - Chemistry en miniature

Goldschmidt-Radical

Peter Keusch




German version






Chemicals:
10 - 4 M  N,N-diphenyl-N'-(2,4,6-trinitrophenyl)-hydrazyl (DPHH) / ethanol 96 %  (20 mg / 500 mL)
lead dioxide

Hazards and safety precautions:

Lead dioxide: Poison. Chronic exposure to lead compounds may lead to a build-up of lead in the body, giving rise to a variety of health problems, including anaemia, kidney and liver damage.
Ethanol is highly flammable.

Safety glasses, protective gloves, suitable ventilation.


Experimental procedure:

Two test tubes are set up as shown in the table below.


Test tube 1 1 mL solution of DPHH  (reference solution)
Test tube 2   1 mL solution of DPHH
PbO2  


A Pasteur pipette contains a small amount of powdery lead dioxide in its tip. The pipette is placed in T2. The lead dioxide is introduced into the solution of DPHH by gentle squeezing of the pipette bulb.


Result:

The yellow solution in T2 turns violet (see Photo below).


Photo
Photo

Discussion:

·   Diphenylpicrylhydrazine is oxidized by PbO2 to diphenylpicrylhydrazyl radical.

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General experimental instructions and index of experiments






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