Step 1: Understanding the Concept:
In polarography, the diffusion current at a dropping mercury electrode depends on how fast the mercury drop grows, since a bigger, faster-growing drop offers more surface area for the electrode reaction.
Step 2: Key Formula or Approach:
Looking at the units in the Ilkovic equation helps identify what each symbol must represent. For the equation to give a current in the correct units, each term must carry its own specific physical quantity: n is a pure number (electrons transferred), D is a diffusion coefficient, t is a time, and C is a concentration.
Step 3: Detailed Explanation:
That leaves m to carry the mercury-related quantity, and since it appears in the equation as \( m^{2/3} \), it must represent a rate with units of mass per unit time, matching how much mercury flows out of the capillary each second. This mass flow rate governs how large each drop grows before it detaches, which in turn sets the electrode's surface area at any instant, directly influencing the measured diffusion current.
Step 4: Final Answer:
In the Ilkovic equation, m stands for the mass flow rate of mercury from the dropping mercury electrode.