At 1 A cm -2 , the cell displayed a standard deviation of  0.75 mV (Table ). This is significantly less than the  3.10 mV reported previously for a comparable, conventional bubbled cell, and was equivalent to around 9% of the current going into production of gas in the form of bubbles. 2.1.4 Gas Bubble Detection at the Anode and Cathode of the Capillary-Fed