ANDREW LAMBERT PHOTOGRAPHY / SCIENCE PHOTO LIBRARY ANDREW LAMBERT PHOTOGRAPHY / SCIENCE PHOTO LIBRARY
Iron-platinum electrochemistry. Platinum electrode (square, lower centre) in a solution of iron (II) and iron (III) ions. The iron (III) ions are being reduced to iron (II) ions, gaining an electron in the process. The electron movements are powered by the oxidation of hydrogen in the smaller tube seen inside the larger tube. Hydrogen gas is adsorbed onto the platinum coil and loses two electrons to form two hydrogen ions in the surrounding water. A platinum-hydrogen electrode is the standard used to measure redox (reduction-oxidation) potentials of ions. In this case the iron (III) to iron (II) redox potential is +0.77 volts.
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