Liquid ozone. Photo by kristofvagyok.
| IUPAC name
| Other names
|Molar mass||48.00 g/mol|
|Appearance||Pale blue gas|
|Density||2.144 kg/m3 (at 0 °C)|
|Melting point||−192.2 °C (−314.0 °F; 81.0 K)|
|Boiling point||−112 °C (−170 °F; 161 K)|
|1.05 g/L (at 0 °C)|
|Solubility||Very soluble in CCl4, chloroform, conc. sulfuric acid|
|Solubility in acetic acid|| 0.0245 g/100 ml (20 °C)|
0.0154 (40 °C)
0.0173 (60 °C)
0.00768 (78 °C)
|Solubility in nitric acid|| aqueous|
0.0012 g/100 ml (25 °C)
0.00099 g/100 ml (35 °C)
0.00078 g/100 ml (45 °C)
0.00039 g/100 ml (68 °C)
|Solubility in aq. NaOH|| 0.00077 g/100 ml (16 °C)|
0.00019 g/100 ml (26 °C)
0.00017 g/100 ml (35 °C)
0.00014 g/100 ml (45 °C)
|Vapor pressure||>1 atm (20 °C)|
Std enthalpy of
|Safety data sheet||OzoneSolutions|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Ozone or trioxygen, is an inorganic molecule with the chemical formula O3. It is an allotrope of oxygen, much less stable than the common diatomic allotrope O2.
Ozone is a powerful oxidant, much more powerful than dioxygen.
Ozone will oxidize most metals (except noble metals) to oxides of the metals in their highest oxidation state. It will also oxidize nitrogen oxides up until dinitrogen pentoxide
- NO + O3 → NO2 + O2
- NO2 + O3 → NO3· + O2
- NO3· + NO2 → N2O5
Solid nitronium perchlorate can be made from NO2, ClO2, and O3:
- 2 NO2 + 2 ClO2 + 2 O3 → 2 NO2ClO4 + O2
It will also oxidize sulphides to sulphates and sulfur and sulfur oxides to sulfuric acid in the presence of water.
- PbS + 4 O3 → PbSO4 + 4 O2
- S + H2O + O3 → H2SO4
- C + 2 O3 → CO2 + 2 O2
This is useful when cleaning glassware that have traces of carbon (such as graphite) that are hard to clean.
- 2 NH3 + 4 O3 → NH4NO3 + 4 O2 + H2O
Ozone also reacts with organic compounds, such as unsaturated compounds to form ozonides.
Ozone is a pale blue gas with a distinctively pungent smell commonly described as that of copy machines, due to commercial copy machine producing small amounts. Some people describe it as "electric", reminiscent of bumper cars from amusement parks. Although electric discharges do produce small amounts of ozone, they also produce nitrous oxide gases, altering the ozone smell. Its liquid form is dark blue and it forms a violet-black solid at extremely low temperatures. It is also unstable at high concentrations, decaying to ordinary diatomic oxygen. It has a varying length half-life, in a sealed chamber at standard conditions, with fan moving the gas, ozone has a half-life of a day.
Ozone is unstable, so it must be generated in situ.
Ozone can be generated from electric discharges in air. Ozone generators work on this principle. However such method also generates nitrous oxides, as air is 78% nitrogen. Feed pure oxygen from a Kipp's apparatus into the generator to produce more ozone and no nitrous oxides. A compressed oxygen tube can also be used.
Another method of generating ozone is decomposition of various highly oxidized or peroxide compounds in acidic solution. An example is decomposition of barium peroxide in sulfuric acid. Alternately, you can use potassium permanganate and mid-strength (50-80%) sulfuric acid. The resulting permanganic acid decomposes, liberating ozone. Avoid using concentrated sulfuric acid, this will give you the anhydride Mn2O7, which is a hair-trigger explosive (but still liberates ozone).
Ozone at concentrations higher than 0.1 ppm in air is dangerous, as it will oxidize organic material indiscriminately. Ground level ozone can harm lung function and irritate the respiratory system. Ozone reacts with compounds lining the lungs to form specific, cholesterol-derived metabolites that are thought to facilitate the build-up and pathogenesis of atherosclerotic plaques (a form of heart disease).
Ozone will react with organic materials to form ozonides, many being explosive.
Ozone will decompose after several hours and has to be made in situ. Cryogenic ozone can be stored (cold causes it to become more stable) but even that is dangerous because liquid ozone is a hair-trigger explosive.
Ozone will decompose to normal oxygen in open air. Make sure you release ozone only outside and never in closed chambers.