Platinum electrode arrangement measuring cell

During measurement, the conductivity cell is filled with an electrolyte solution this cell is usually made of glass with sealed platinum electrodes. Various shapes are used, depending on the purpose that it is to serve. Figure 2.9 depicts examples of suitable cell arrangements. The electrodes are covered with platinum black, to avoid electrode polarization. The electrodes are placed close to one another in poorly conductive solutions and further apart in more conductive solutions. 

The conductivity cell is modified from a conventional type. It is made of borosilicate glass, which resists the attack of anhydrous chlorine and bromine trifluorides, and is equipped with two smooth platinum electrodes to minimize electrode corrosive effects. These electrodes are approximately 12x25 mm. in size, held 1.5 mm. apart with borosilicate glass spacers. The arrangement of electrodes and leads is shown in Figure 1. An internal thermocouple well leads from the top of the cell to a point near the electrodes and contains a copper constantan thermocouple. The cell constant is determined by measuring the cell resistance... 

The measurements were conducted by applying the cell in oxidic melts containing small and equal molar concentrations of antimonyflll) and antimonyfV) (or arsenic(lll) and arsenic(V)) oxide. The special arrangement used separated the melt essentially from the surrounding atmosphere and allowed electrochemical pumping of oxygen into, and out of, the melt by means of a platinum electrode and a zirconia electrode or the zirconia crucible, which contained the melt and served as the oxide ion-conducting wall [28]. The concentration ratio of the polyvalent ionic species could thus be well adjusted. 

Figure 26-13. Arrangement of cells for measuring oxygen fugacities in a streaming nonisothermal melt by referring to only one nonisothermal dissolving zirconia reference electrode (see Equation 26-35). E, and = measured emfs Th = thermocouples measuring indicated temperatures = temperature of reference electrode = temperature at contact ZrO/melt , and T 2 temperatures of platinum measuring electrodes.

The thickness of the TEL is measured by the arrangement also shown in Fig. 4.11. A very fine platinum needle is welded on a micrometer screw and the micrometer is fixed at a position right above the electrode. When the cell is arranged, the Pt needle is adjusted slowly toward the electrode. Once the needle touches the electrode surface, there will be a sudden value shown on the ohmmeter, then the move of the needle is stopped and the position of the micrometer is recorded. Afterwards the micrometer is moved backward until some distance is kept between the electrode and the tip of the needle, and then the electrolyte is poured into the cell to form a relative thick electrolyte film on the electrode. Then the micrometer is moved towards... 

The Standard Potential of Chlorine. Measurements of the potentials of galvanic cells without liquid junctions from which the standard potential of chlorine may be deduced have been made by Lewis and Ruppert40 who used, as one electrode, platinum over which a mixture of chlorine and nitrogen was bubbled, and, as reference, a calomel electrode and hydrochloric acid as electrolyte. The arrangement may be represented by... 

In the second practical arrangement of the cell, which is shown in Figure 26-3 b, the platinum measuring electrode and Zr02 ceramic are in intimate contact, and the set-up could be called a single-rod electrode . The cell scheme is represented by... 

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