**2.2 Bubble size measurement**

The purpose is to demonstrate that the electrochemical probe can be used as a means of measuring bubble sizes. First, calibrated bubbles are used by single tubes. Then, a gas injector is used in a bubble column with homogeneous bubbling regime. In this case, the average frequency of the fluctuations of diffusion limited current detected by the probe is postulated as being equal to the bubble frequency leading to an estimation of bubble size.
