The Color of Ozone

Does ozone gas have a color? Yes, the color is blue. The problem is, ozone is normally found in gas, or in water at such low concentrations that the color is not visible.

Recently we performed some lab testing that required ozone levels in water greater than 100 ppm. The picture below provide some great examples of the color of ozone.


ozone color
0 ppm ozone on left vs >100 ppm ozone on right


Ozone in water
The Color of Ozone is visible in this image


ozone in water
An ATI Q45 Dissolved Ozone Monitor was used to measure dissolved ozone in water. The blue color of the water is even slightly visible in the flow cell used to measure ozone.


Dissolved Ozone in water
AS the dissolved ozone level increases the color of the water gets darker. The blue color in the water starts to become visually evident above 50 ppm.


Ozone levels in water turn water blue
The blue color of ozone is more visual in larger containers like this 1-gallon water jug.


Ozone Properties

The table below provides additional information on the properties of ozone. This shows the color of ozone is light blue, which is true. It is only visibly blue when ozone gas or ozone in water is at a very high concentration.

Property Ozone Oxygen
Molecular Formula O3 O2
Molecular Weight 48 g/mol 32 g/mol
Color Light blue Colorless
Smell Odor threshold of 0.001 ppm, pungent at high levels Odorless
Melting Point -192.5 deg C -218.79 deg C
Boiling point -111.9 deg C -1892.95 deg C
Critical Temperature -121 deg C -118.56 deg C
Critical Pressure 54.5 atm 5.043 atm
Density 2.144 g/l @ 0 deg C 1.429 g/l @ 0 deg C
Solubility @ 0 deg C 0.64 g/100 ml 0.049 g/100 ml
Electrochemical Potential 2.07 V 1.23 V


Ozone Solubility

Ozone is only partially soluble into water. The graph below shows the solubility of ozone into water based on water temperature and ozone gas concentration. As the water temperature decreases and ozone concentration increases ozone becomes more soluble into water.

Water pressure is the third and final factor in determining ozone solubility into water. However, as these images were taken of water at ambient pressure, this was not a factor used, and is not a required factor in achieving high ozone levels into water.

Do you have a need to achieve higher ozone levels into water? Or lab testing that requires dissolved ozone levels higher than off-the-shelf equipment can provide? Give us a call, we would be glad to help.