Electrode compartment

Combination electrodes have increased in use and are a consoHdation of the glass and reference electrodes in a single probe, usually in a concentric arrangement, with the reference electrode compartment surrounding the pH sensor. The advantages of combination electrodes include the convenience of... 

Free flow. Dobry and Finn [Chem. Eng. Prog., 54, 59 (1958)] used upward flow, stabilized by adding methyl cellulose, polyvinyl alcohol, or dextran to the background solution. Upward flow was also used in the electrode compartments, with cooling efficiency sufficient to keep the main solution within 1°C of entering temperature. 

The liquid membrane (thickness 0.2 cm) was separated from the aqueous solutions by two vertical cellophane films.The electrode compartments were filled with 0.05 M sulfuric acid solutions and were separated by the solid anion-exchange membranes MA-40. Binary mixtures contained, as a mle, 0.04 M Cu(II) and 0.018 M Pt(IV) in 0.01 M HCl. 0.1 M HCl was used usually as the strip solution. 

When internal generation is used in association with a platinum auxiliary electrode the latter must be placed in a separate compartment contact between the auxiliary electrode compartment and the sample solution is made through... 

Chemists use a special notation to specify the structure of electrode compartments in a galvanic cell. The two electrodes in the Daniell cell, for instance, are denoted Zn(s) Zn2+(aq) and Cu2+(aq) Cu(s). Each vertical line represents an interface between phases—in this case, between solid metal and ions in solution in the order reactant product. 

In this expression, E° is the standard emf of the cell, the emf measured when all the species taking part are in their standard states. In practice, this condition means that all gases are at 1 bar, all participating solutes are at 1 molT-1, and all liquids and solids are pure. For example, to measure the standard emf of the Daniell cell, we use 1 M CuS04(aq) and a pure copper electrode in one electrode compartment and 1 M ZnS04(aq) and a pure zinc electrode in the other. 

Self-Test 4A Write the diagram for a cell with a hydrogen electrode on the left and an irnn(III)/irnn(lI) electrode on the right. The two electrode compartments are connected by a salt bridge and platinum is used as the conductor at each electrode. 

Therefore, by measuring E, we can infer the concentration of Ag in the left-hand electrode compartment. If the concentration of Ag+ ions in the left-hand electrode is less than that in the right, then E > 0 for the cell as specified and the right-hand electrode will be found to be the cathode. 

Each electrode compartment of a galvanic cell contains a silver electrode and 10.0 ml, of 0.10 M AgN03(aq) they are connected by a salt bridge. You now add 10.0 ml. of 0.10 M NaCl(aq) to the left-hand electrode compartment. Almost all the silver precipitates as silver chloride but a little remains in solution as a saturated solution of AgCI. The measured emf is E = +0.42 V. What is the concentration of Ag+ in the saturated solution ... 

In a simple version of a fuel cell, a fuel such as hydrogen gas is passed over a platinum electrode, oxygen is passed over the other, similar electrode, and the electrolyte is aqueous potassium hydroxide. A porous membrane separates the two electrode compartments. Many varieties of fuel cells are possible, and in some the electrolyte is a solid polymer membrane or a ceramic (see Section 14.22). Three of the most promising fuel cells are the alkali fuel cell, the phosphoric acid fuel cell, and the methanol fuel cell. 

Figure 16 shows a diagram of a small cell, working electrode compartment 10 cm , which combines many of the features discussed above. 

Reference electrodes for non-aqueous solvents are always troublesome because the necessary salt bridge may add considerable errors by undefined junction potentials. Leakage of components of the reference compartment, water in particular, into the working electrode compartment is a further problem. Whenever electrochemical cells of very small dimensions have to be designed, the construction of a suitable reference electrode system may be very difficult. Thus, an ideal reference electrode would be a simple wire introduced into the test cell. The usefulness of redox modified electrodes as reference electrodes in this respect has been studied in some detail... 

The single cell thus fabricated was placed in a single chamber station as illustrated in Fig. 2. A humidified mixture of methane and oxygen was supplied to the station so that both electrode compartments were exposed to the same composition of methane and oxygen. For the measurement of the cell temperature, a thermocouple (TC) was placed approximately 4 mm away from the cathode site. For the evaluation of the fuel-cell performance, Ft wires and Inconel gauzes were used as the output terminals and electrical collectors, respectively. 

Figure 16.5 Schematic of the electrochemical array cell. CE, counter-electrode compartment WE, working electrode compartment RE, reference electrode compartment GS, glass sinter GS/GI, gas inlet with glass sinter.

It is most important, of course, also to solve the diaphragm problem of mutually separating the generator and counter electrode compartments, either... 

Fig. 2.10 Schematic design of a cell for the determination of transport numbers from measurements of the concentration decrease in electrode compartments (Hittorf s method)...

Thus, the transport number can be found from measurement of the decrease in the amount of the salt in the electrode compartments. 

Figure 26. EXAFS spectroelectrochemical cell (A) front view, (B) top view, (C) side view, (D) assembly (a) auxiliary electrode compartment, (b) working electrode well, (c) reference electrode compartment, (d) X-ray window, (e) inlet port, (f) auxiliary electrode lead, (g) RVC working electrode, (h) Pt syringe needle inlet and electrical contact, (i) Pt wire auxiliary electrode, (j) Ag/AgCl(3M NaCl) reference electrode. (From Ref. 98, with permission.)...

Figure 2.105 Optically transparent thin layer electrochemical (OTTLE) cell. A = PTFE cell body, B = 13 x 2 mm window, (C and E) = PTFE spacers, D = gold minigrid electrode, F = 25 mm window, G = pressure plate, H = gold working electrode contact, 1 = reference electrode compartment, J = silver wire, K = auxiliary electrode and L = solution presaturator. From Ranjith...

Large reservoirs of buffer solution are maintained in the electrode compartments to minimize the effect of electrolysis which is to produce hydrogen ions at the anode and hydroxyl ions at the cathode. The choice of buffer is critical in its effect on the degree of separation of a mixture, and is dictated largely by the values of the various dissociation constants. 

Draw a double vertical line to represent the salt bridge connecting the two electrode compartments Zn(s) I Zn2+(1 M) II... 

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