Ozone as a UV Inhibitor

This experiment shows how ozone absorbs light at 254 nm. The ozone is generated in an home-built Siemens-ozoniser. This apparatus consists of a high-voltage source generating about 20kV at 3 mA/33kHz,

A modified spherical cooler (the outside is wrapped with aluminum-foil, which is grounded, the inner part (the spheres) is filled with water containing some potassium nitrate (as conducting salt) and the coolant is replaced by a slow flow of pure oxygen from a bottle. The inner electrode (the liquid) is connected to the high-voltage generator. When the generator is turned on a corona-discharge takes place where the oxygen flows. This discharge excites the oxygen which reacts to (creates) ozone.

The absorption of the ultraviolet light is shown with some chromatography plates (fluorescent at 254 nm, the green color results from fluoresecence caused by two mercury lamps illuminating the plates at 254 nm. The flow of ozone (about 15% in oxygen) is inserted between the source of the uv-light and the dc-plates, the ozone absorbs the light and no more fluorescence is visible behind it. This makes the invisible gas visible using invisible light.

Courtesy of:
Dr. rer. nat. Björn Dingwerth
Diplom-Chemiker
Merowingerstr. 23
40223 Düsseldorf

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Moral of the story: Do not use UV lamps that produce ozone for your display lights. (plus, ozone just ain’t healthy)

 Even with lamps that are “ozone free” consider a fan to blow away the ozone that they “don’t” generate (they all do, to some degree)