Saturation of a Hydrogen Electrode by Electrolysis of a Solution
Abstract Generated abstract
This paper proposes a method for using a hydrogen electrode in pH measurements without an external supply of purified hydrogen. The authors saturate a platinized platinum or palladium measuring electrode by electrolyzing the solution under investigation, using an auxiliary platinum electrode connected to a direct current source so that hydrogen is generated directly at the measuring electrode. Experiments in acidic, alkaline, and buffer solutions show rapid establishment and sustained stability of the electrode potential, with measured potentials relative to a calomel electrode following the theoretical pH dependence of a reversible hydrogen electrode. The method is presented as suitable for automated monitoring of hydrogen ion activity in technological solutions, including high temperature and high pressure applications.
Full Text
N. V. Podbornov, V. N. Titov
Saturation of a Hydrogen Electrode by Electrolysis of a Solution
(Presented by the scientific seminar of the departments)
When measuring the pH of various technological solutions, in a number of cases—especially at high temperatures and pressures—a hydrogen electrode may be used. One of the principal shortcomings, limiting—
Fig. 1. Dependence of the established e.m.f. on the pH of solutions: 1—sulfuric acid solutions; 2—acetate buffer; 3—borax solutions; 4—calcium oxide hydrate solution.
A factor hindering its practical use is the need to supply pure hydrogen, which makes it necessary to have special apparatus for obtaining and purifying this hydrogen. In addition to the inconvenience, the presence of such apparatus creates a substantial fire hazard and requires special care in handling it. According to the proposed method, saturation of the hydrogen electrode is carried out by electrolysis of the solution under investigation. For this purpose, a third auxiliary platinum electrode is introduced into the solution and connected to the positive pole of a direct-current source. The negative pole is connected to the measuring platinum (or palladium) electrode, coated with platinum black. The hydrogen liberated as a result of electrolysis is collected under the bell of the platinized electrode and saturates it; the electrode acquires the properties of a reversible hydrogen electrode. In acidic, alkaline, or buffer solutions the potential is established rather rapidly and does not fall off for a considerable time. The dependence of the established potentials, relative to the calomel electrode, on pH for a series of solutions is shown in the figure. The pH of the solutions was measured with a glass electrode. As can be seen from the graph, the straight line drawn through the experimental points corresponds to the theoretical one for the hydrogen electrode.
The measurement process is readily automated by using an automatic switching device and can be successfully applied for the automatic monitoring of the active concentration of hydrogen ions in technological solutions, for example, sulfuric acid solutions at elevated temperature and pressure.