Electrode reaction cannot be reversed, and the identities of the anode and cathode are therefore fixed. The anode is always the negative electrode. The cell can be discharged but not recharged. A secondary cell, for example a rechargeable battery, is a cell in which the chemical reactions are reversible. When the cell is being charged, the anode becomes the positive (+) and the cathode the negative (−) electrode. This is also the case in an electrolytic cell. When the cell is being discharged, it behaves like a primary cell, with the anode as the negative and the cathode as the positive
Polarograph Polarograph A Polarograph is a chemical analysis instrument used to record automatic voltage-intensity curves. The Polarograph uses an electrolytic cell consisting of an electrode or microelectrode small area, generally of mercury drop type , which is a very fine capillary tube through which mercury flows slowly , which comes in the form of small droplets, which fall on the same surface of a much broader element, which is the other electrode . When one applies a variable voltage in this cell, the electrode large area remains unchanged, while the microelectrode undergoes a change of potential ,( i.e. is polarized). It