Introduction: A reference electrode is an electrode that serves as a reference comparison when measuring various electrode potentials. The electrode to be measured and the reference electrode of which the potential value of the electrode is accurately known are formed into a battery, and the value of the electromotive force of the battery is measured to calculate the electrode potential of the electrode to be measured. The electrode reaction performed on the reference electrode must be a single reversible reaction with stable and reproducible electrode potential. Usually a slightly soluble salt electrode is used as the reference electrode, and the hydrogen electrode is only an ideal but not easy to realize reference electrode. A list of commonly used reference electrodes is given below. Scope of application of various reference electrodes: Use a DC voltmeter with appropriate input impedance, test leads, and a stable reference electrode, such as a saturated copper/copper sulfate reference electrode (CSE), silver/silver chloride electrode (Ag/AgCl), or saturated potassium chloride (KCl) calomel electrode, the pipeline-to-electrolyte potential measurement can be performed. When the electrolyte is soil or fresh water, it is generally measured with CSE, but it is not applicable in seawater. When using CSE in a high chloride environment, the stability of the CSE must be checked before validating the readings. Silver/silver chloride electrodes are commonly used in seawater environments, and saturated potassium chloride calomel electrodes are more commonly used in laboratories. However, multifaceted polymer colloid-saturated KCl calomel electrodes can also be used, but the contact area to the environment needs to be appropriately increased. Choice of reference electrode: Neutral system - silver silver chloride electrode, saturated calomel electrode (filled with saturated potassium oxide solution) Acidic system - mercurous sulfate electrode (filled with saturated potassium sulfate solution) Alkaline system - mercury mercury oxide electrode (filled with 1 mol potassium hydroxide solution) basic requirements: A reference electrode is a reversible electrode system that has a stable and reproducible reversible electrode potential under specified conditions. Usually the main requirements for a reference electrode are: (1) The reversibility of the electrode is relatively good, and it is not easy to polarize. This requires the reference electrode to be a reversible electrode with a high exchange current density (>10A/cm). When the current flowing through the electrode is less than 10A/cm, the electrode is not polarized. Even if a slightly larger current flows for a short time, the potential can quickly return to the original value after the power is turned off. (2) The electrode potential is relatively stable and close to zero potential, so it is not easy to be polarized or passivated. After the reference electrode is made, its potential should be stable after standing for several days. (3) The potential reproducibility is good. The potential of the same reference electrode made by different people or each time should be the same. The potential of each reference electrode produced each time should be the same after stabilization, and the difference should be less than 1 mV. (4) The temperature coefficient is small, that is, the potential changes little with temperature. And when the temperature returns to the original temperature, the potential should quickly return to the original potential value. (5) The preparation, actual use and maintenance are more convenient and durable. Reference electrodes that can meet the above requirements include hydrogen electrode, calomel electrode, mercurous sulfate electrode, mercuric oxide electrode, silver chloride electrode, etc. Most of these electrodes are type II electrodes.
Introduction: A reference electrode is an electrode that serves as a reference comparison when measuring various electrode potentials. The electrode to be measured and the reference electrode of which the potential value of the electrode is accurately known are formed into a battery, and the value of the electromotive force of the battery is measured to calculate the electrode potential of the electrode to be measured. The electrode reaction performed on the reference electrode must be a single reversible reaction with stable and reproducible electrode potential. Usually a slightly soluble salt electrode is used as the reference electrode, and the hydrogen electrode is only an ideal but not easy to realize reference electrode. A list of commonly used reference electrodes is given below.
