The utilization of a wire-mesh sensor for the measurement of chemical species conversion during the chemical adsorption of carbon dioxide in sodium hydroxide solution is reported for the first time. The wire-mesh sensor obtains cross-sectional images of the liquid-phase conductivity, which changes with the consumption of hydroxide during the reaction. A theoretical model was applied to verify the use of conductivity as an indicator for the reaction progress. Experiments were carried out using a lab-scale bubble column reactor with two wire-mesh sensors at different reactor heights. The results obtained from the reactor model and experiments showed very good agreement and demonstrate the potential of this imaging instrument to follow the course of a chemical reaction via ionic species concentration even in a dense bubbly flow. This way, a better understanding of the coupling of hydrodynamics, mass transfer, and reaction in bubble columns and other reaction devices can be achieved.