What is Ozone?

Discovered by Christian Friedrich Schonbein in 1840, Ozone is triatomic oxygen with the chemical formula O3.  It derives its name from the Greek word ozein or ogeiv, “to smell or smell.” 
Ozone gas is light blue at room temperature and has a characteristic pungent odor.  Physical 
property data is provided in the table below:

Molecular Weight	48 g/mole
Density Relative to Air	1.66
Specific Weight at 0 degree C & 760 mm Hg	2.143 kg/m3
Heat of Formation	34.5 kcal/mole
Boiling Point	-112 degrees C (dark blue liquid)
Melting Point	-193 degrees C (dark red or blue solid)

At standard temperature and pressure ozone is a blue gas. Ozone forms a dark blue liquid below -112 °C and a dark blue solid below -193 °C. Ozone is a powerful oxidizing agent, and is unstable, decaying to ordinary oxygen through the reaction:  2O3 → 3O2. 

Typical Ozone Lifetime as a Function of TemperatureGaseous                                                                        Dissolved in Water (pH 7)
Half Life Time        Temperature                                   Half Life Time        Temperature
3 months                -50 C                                                30 minutes             15 C
18 days                  -35 C                                                20 minutes              20 C
8 days                    -25 C                                                15 minutes              25 C
3 days                     20 C                                                12 minutes              30 C
1.5 hours                120 C                                                 8 minutes              35 C
1.5 seconds            250 C                                               

Values based on thermal decomposition only, does not consider chemical reactions, wall and catalytic effects.

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