Experiment OC 1.1 Oscillating Platinum Wire

1. Methanol being heated in an Erlenmeyer flask 2. Platinum wire heated until glowing
Methanol (dyed blue) is heated A platinum wire is heated till glowing
3. Platinum wire hanging over methanol 4. Methanol ignites
The glowing platinum wire is hung over the methanol The methanol ignites
5. This process repeats ... 6. ... until all the methanol has combusted
This process repeats itself ... ... until all the methanol has combusted.
Animation of Experiment (GIF Format, 524 k)
Animation of Experiment (MPEG Format, 913 k)
Photo 1: Methanol (dyed with methyl blue) is heated in an Erlenmeyer flask.
Photo 2: Simultaneously, a platinum wire is heated until glowing. The wire is next hung in the Erlenmeyer flask.
Photo 3: At first, the platinum wire glows weakly. After a short amount of time, however, it begins to glow more intensely. The cause is the catalytic oxidation of methanol to formaldehyde according to the following equation:

CH3OH + 1/2 O2 ® CH2O + H2O

This exothermic reaction, which takes place directly on the outer surface of the platinum wire, causes the wire to heat up.
Photo 4: At a given temperature, the wire ignites the methanol/air mixture, which burns with a green flame:

CH3OH + 1.5 O2 ® CO2 + 2 H2O

The flames are extinguished when the oxygen present in the air in the flask is consumed. In order to make the flames more visible, boric acid and concentrated sulfuric acid (catalyst) are added to the methanol. This forms the volatile boric acid trimethyl ester, which burns with a green flame:

B2O3 + 6 CH3OH Acid catalyst 2 B(OCH3)3 + 3 H2O
Photos 5 + 6: The process repeats itself periodically as long as methanol is available and as long as the flask is constantly replenished with a fresh stream of oxygen-containing air.
back