Electrode amalgam reference

Metal and Metal Amalgam Reference Electrodes Other Than Silver... 

Reference Electrodes and Liquid Junctions. The electrical cincuit of the pH ceU is completed through a salt bridge that usually consists of a concentrated solution of potassium chloride [7447-40-7]. The solution makes contact at one end with the test solution and at the other with a reference electrode of constant potential. The Hquid junction is formed at the area of contact between the salt bridge and the test solution. The mercury—mercurous chloride electrode, the calomel electrode, provides a highly reproducible potential in the potassium chloride bridge solution and is the most widely used reference electrode. However, mercurous chloride is converted readily into mercuric ion and mercury when in contact with concentrated potassium chloride solutions above 80°C. This disproportionation reaction causes an unstable potential with calomel electrodes. Therefore, the silver—silver chloride electrode and the thallium amalgam—thallous chloride electrode often are preferred for measurements above 80°C. However, because silver chloride is relatively soluble in concentrated solutions of potassium chloride, the solution in the electrode chamber must be saturated with silver chloride. 

Reductant equivalent weights of, 847 Reduction 409 by chromium(II) salts, 409 by hydrogen sulphide, 416 by Jones reductor (zinc amalgam), 410 by liquid amalgams, 412 by silver reductor, 414 by sulphurous acid, 416 by tin(II) chloride, 415 by titanium(II[), 410 by vanadium(II), 410 see also Iron(III), reduction of Reduction potentials 66 Reference electrodes potentials, (T) 554 Relative atomic masses (T) 819 Relative error 134 mean deviation, 134... 

Rabenstein and Yamashita [52] determined penicillamine and its symmetrical and mixed disulfides by HPLC in biological fluids. Plasma and urine were deproteinized with trichloroacetic acid, and HPLC was performed on a column (25 cm x 4.6 mm) or Biophase ODS (5 pm) with a mobile phase comprising 0.1 M phosphate buffer (pH 3) and 0.34 mM Na octylsulfate at 1 mL/min. Detection was with a dual Hg-Au amalgam electrode versus a Ag-AgCl reference electrode. (z>)-penicillamine and homocysteine were determined at the downstream electrode at +0.15 V, and homocystine, penicillamine-homocysteine, and penicillamine disulfides were first reduced... 

Lebel [224] has described an automated chelometric method for the determination of sulfate in seawater. This method utilises the potentiometric end-point method for back titration of excess barium against EDTA following precipitation of sulfate as barium sulfate. An amalgamated silver electrode was used in conjunction with a calomel reference electrode in an automatic titration assembly consisting of a 2.5 ml autoburette and a pH meter coupled to a recorder. Recovery of added sulfate was between 99 and 101%, and standard deviations of successive analyses were less than 0.5 of the mean. 

An alternative method was described by Pinzauti et al (40) for determination of several antithyroid drugs potentimetrically with 0.01 M mercuric acetate with use of a mercuric sulfate reference electrode and an amalgamated gold or a silver indicator-electrode. The method is rapid and the results are reproducible the errors are all within + 0.38%. 

Figure 4.13 — (A) Serially arranged ISEs for the simultaneous determination of sodium, potassium, calcium and chloride ions. (B) Serially and parallelly arranged ISEs for the simultaneous determination of T, Br", Cl and F . WE working electrode PC personal computer Ej-E r, Cr, Br" and F ISEs, respectively C C3 amalgamated-lead columns (1.5 and 2.5 cm long, respectively) AgCl column RE reference electrode PHM pH/mV-meter S sample injection CS carrier stream P pump R chart recorder W waste. (Reproduced from [126] and [127] with permission of Elsevier Science Publishers and Pergamon Press, respectively).

Electrode materials may be liquid or solid metals, amalgams, References pp. 74—78... 

Figure 16.4 Cyclic voltammogram of 4.5 mM 2,3-dinitro-2,3-dimethylbutane in N,N-dimethylformamide/0.20 M Bu4NPF6 at a 25-pm-diameter mercury electrode. Curves experimental voltammograms after subtraction of background current. Points digital simulations. Potentials referred to cadmium reference electrode [cadmium amalgam/CdCl2 (sat d) in DMF]. [Reprinted with permission from W.J. Bowyer and D.H. Evans, J. Org. Chem. 53 5234 (1988). Copyright 1988 American Chemical Society.]...

Various attempts have been made to circumvent these problems and to eliminate junction potentials, including (1) extrapolation procedures designed to eliminate the difference between the compositions of the two solutions in the appropriate limit, (2) separation of the two solutions by means of a doublejunction salt bridge, (3) the use of double cells with dilute alkali metal amalgam connectors, and (4) the use of glass or other types of ion-specific electrodes as bridging reference electrodes. 

Other reference electrodes for use in polar aptotic solvents. Emphasis has been given to the use of the silver-silver ion reference electrode because it is almost universally applicable, and because standardization on the use of one reference electrode system simplifies the comparison of data between different workers. However, a number of other reference electrodes have been used (see Table 5.4), particularly those that have resulted from the vast amount of batteiy research. These include the Li/Li(solv)+ and other alkali metal electrodes that function reversibly in Me2SO, propylene carbonate, and hexa-methylphosphoramide. The thallium-thallous halide electrodes of the second kind also function reversibly in Me2SO and propylene carbonate. The cadmium amalgam-cadmium chloride reference electrode also functions reversibly in dimethylformamide and may be a useful substitute for the silver-silver ion reference electrode, which may be unstable in dimethyformamide.54... 

Silver solid amalgam can be used for the preparation of a - reference electrode of second kind (-> electrode of second kind) [iv]. 

TI+/TI(Hg) electrode — A -> reference electrode commonly known as Thalamid electrode employing thallium amalgam (40wt%) as electronically conducting phase and an aqueous solution of KC1 (saturated or 3.5 M) saturated with T1C1. In comparison with the saturated calomel electrode it shows a superior temperature stability up to T = 135 °C without temperature hysteresis, no disproportionation of T1C1 (as compared to Hg2 CI2) or significant complexation are found. 

The solution to the right of the glass electrode is usually a buffer solution of KH2P04 and Na2HP04, with 0.1 mol dm"3 of NaCl. The reference electrode is usually a calomel electrode, silver/silver chloride electrode, or a thallium amalgam/thallous chloride electrode. The emf of this cell depends on a(H + ) in the solution X in the same way as that of the cell with the Pt H2 electrode, and thus the same procedure is followed. 

A zinc amalgam electrode has been employed as reference electrode in dimethyl sulfoxide (DMSO) [205] and ammonia [206]. The saturated zinc amalgam was prepared [207] by electrolytic deposition of zinc into a layer of pure mercury from an aqueous ZnS04 solution. The solution in equilibrium with the Zn(Hg) consisted of a saturated solution of Zn(C104)2, 4DMSO or ZnCF, 6NH3. 

As reference electrode [211] for polarographic work, an aqueous or methanolic calomel electrode, connected to the DMSO solution with a suitable salt bridge to avoid contamination, has been used. The most stable reference electrodes in DMSO seem to be the amalgam electrodes, such as Tl(Hg)/TlCl [214] or Li(Hg)/LiCl [207]. 

The E.M.F. of a similar cell, in which the electrodes are pure solid cadmium and the saturated amalgam, is 0.05045 volt at 25 C. Determine the activity and activity coefficient of the cadmium in both amalgams referred to in the preceding paragraph, taking pure solid cadmium as the standard state. 

In Eq. (155) K(Hg) is a potassium amalgam electrode connected to a solution of KCl at concentration c in solvent S AgCl(s)/Ag(s) is the silver/silver chloride reference electrode. 

The use of cadmium and zinc bars as reference electrodes ) had become an established practice in the storage battery industry by the time that Nernst was concerning himself with the problem of a standard. Ostwald ( ) also mentions that in earlier times amalgamated zinc in a concentrated zinc sulfate solution was used as a constant electrode and occasionally as a reference electrode but that its use posed some serious problems. 

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