Standard calomel electrode

The electrolysis is carried out at a reference potential of -2.4 volts vs a standard calomel electrode. An initial current density of 0.0403 amp/cm is obtained which drops to 0.0195 amp/cm at the end of the reduction, which is carried on over a period of 1,682 minutes at 15° to 20°C. The catholyte is filtered, the solid material is washed with water and dried. 430 g of the 2,3-bis-(3-pyridyl)-butane-2,3-diol is recrystallized from water, MP 244° to 245°C. 

Example.—The electro-affinities of Cu and Zn in normal ( = ) solutions of their salts are - - 0 606 and — 0 493 volt, referred to the standard calomel electrode ... 

Suppose the reference electrode for Table 12.1 were the standard calomel electrode, Hg2Cl2/Hg,Cl ([Cl ] =... 

Consider the question posed in Exercise 12.49 except that a saturated calomel electrode (the solution is saturated with KCI instead of having [Cl = 1.00 mol-L ) is used in place of the standard calomel electrode. How will this replacement change the answers given in Exercise 12.49 The solubility of KCI is 35 g/(100 rnL H,0). 

Figure 2 Selective electrochemical detection of a mixture on multielectrode amper-ometry. AA = Ascorbic acid, NE = norepinephrine, DOPAC = 3-4-dihydroxy-phenylacetic acid, E = epinephrine bitartrate, 5-HIAA = 5-hydroxyindole-3-acetic acid, HVA = homovanillic acid, TRP = tryptophan, 5-HT = 5-hydroxytryptamine, and 3-MT = 3-methoxytyramine (separated by RPLC). Detection was with a 4-electrode glassy carbon array, with electrode 1 at 500 m V) electrode 2 at 700 mV, electrode 3 at 900 mV, and electrode 4 at 1100 mV. Note that at electrode 1, HVA, TRP, and 3-MT are not seen. At electrode 2, only TRP is not seen. A standard calomel electrode was used as reference. (Reprinted with permission from Hoogvliet, J. C., Reijn, J. M., and van Bennekom, W. P., Anal. Chem., 63, 2418, 1991. 1991 Analytical Chemistry.)...

A method has been developed for differentiating hexavalent from trivalent chromium [33]. The metal is electrodeposited with mercury on pyrolytic graphite-coated tubular furnaces in the temperature range 1000-3000 °C, using a flow-through assembly. Both the hexa- and trivalent forms are deposited as the metal at pH 4.7 and a potential at -1.8 V against the standard calomel electrode, while at pH 4.7, but at -0.3 V, the hexavalent form is selectively reduced to the trivalent form and accumulated by adsorption. This method was applied to the analysis of chromium species in samples of different salinity, in conjunction with atomic absorption spectrophotometry. The limit of detection was 0.05 xg/l chromium and relative standard deviation from replicate measurements of 0.4 xg chromium (VI) was 13%. Matrix interference was largely overcome in this procedure. 

Electron mediators successfully used with oxidases include 2,6-dichlorophenolindophol, hexacyanoferrate-(III), tetrathiafulvalene, tetracyano-p-quinodimethane, various quinones and ferrocene derivatices. From Marcus theory it is evident that for long-range electron transfer the reorganization energies of the redox compound have to be low. Additionally, the redox potential of the mediator should be about 0 to 100 mV vs. standard calomel electrode (SCE) for a flavoprotein (formal potential of glucose oxidase is about -450 mV vs SCE) in order to attain rapid vectrial electron transfer from the active site of the enzyme to the oxidized form of the redox species. 

The reaction is considered to proceed via a silyl anion mechanism, although the possibility of a radical-based mechanism has also been discussed.115,125 In order to clarify the mechanism, coupling experiments on a 1 1 mixture of chlorotrimethylsilane, 27 (reduction potential <—3.0 V),126 and chlorotriphenylsilane, 28 (reduction potential vs. standard calomel electrode (SCE) < —3.0 V),120 were performed, in which the mixed coupling product 1,1,1-trimethyl-2,2,2-triphenyldisilane, 29, and the homocoupling product hexaphenyldisilane, 30, only, were found,125 as indicated in Scheme 15. 

Examples (a) Titration of Mg2+ with 8-hydroxyquinoline. In this particular instance, a diffusion current for 8-hydroxyquinoline is normally achieved at - 1.6 V Vs Standard Calomel Electrode (SCE), whereas Mg2+ ion is more or less inert at this potential. 

Amino acids enhance the oxidation peak of Cu(0) obtained with a carbon paste electrode incorporating Cu(II) cyclohexylbutyrate. The increased current is proportional to the amino acid concentration at trace levels in the pM range373. The behavior of such electrodes was investigated for cysteine (115). On scanning potentials in the positive direction, the amino acid is accumulated on the electrode as the Cu(I) complex at +0.90 V vs a standard calomel electrode (SCE), in acetate buffer at pH 4.5 linear range is 2 x 10 9 to 1 x 10-7 M, 1 min accumulation, RSD 3% (n = 5)374,375. 

Figure 3.5 A grid which allows the interconversion of potentials between the standard calomel electrode (SCE) and the standard hydrogen electrode (SHE). In addition, the standard electrode potentials of two couples, i.e. Zn " ", Zn and Fe +, Fe, are shown for comparative purposes.

Electrochemically, the BF4 anion was found to be stable against oxidation on a glassy carbon (GC) surface up to 3.6 V vs a standard calomel electrode (SCE), which translates into - 5.0 V vs lithium. When a distinction is made, this stability limit is somehow lower than those of AsFe and PFe anions however, caution must be exercised here, as these data were measured on GC with quaternary ammonium as supporting electrolyte, instead of on a surface of cathode materials. This could result in substantial difference. ... 

Fig. 4.1 Skeleton structure of a photoelectrochemical cell (PEC) comprised of a photoanode and cathode. Potentials of both are measured with reference to a third electrode, the standard calomel electrode.

The outer-sphere one-electron reduction of CO2 leads to the formation of the 02 radical anion. In dry dimethylformamide, the C02/ C02 couple has been experimentally determined to be —2.21 V vs. standard calomel electrode (SCE) or approximately —2.6 V vs. the ferrocene/ferrocenium couple [21,22]. From pulse radiolysis experiments, the reduction potential of CO2 is —1.90 V vs. the SHE in water (—2.14 V vs. SCE) [23]. Theoretical calculations have been used to calculate the contributions of various factors to the reduction potential of CO2. These include the electron affinity of CO2,... 

All aqueous potential values are referenced to the standard hydrogen electrode. Nonaqueous potential values are referenced to ferrocene (Fc) if possible. Other references are indicated in parentheses where SCE represents the standard calomel electrode, A1 represents the Ag/Ag+ reference electrode ([Ag+] = 0.01 M unless otherwise indicated) and A2 represents the Ag/AgCl reference electrode. In acetonitrile, potential values referenced to SCE may be corrected to the ferrocene reference standard by subtracting 0.380 V, depending upon the anion present (a) Ref 11, (b) Ref 10c. c [Ag+] = 0.1 M. 

Fig. 3.5,19 Open-circuit voltage (K. ) for CdS formed in 9-layer CdAr films as a function of particle size (estimated from UV/visible absorption spectra). The electrolyte was 1.0 M Na2S03 at pH 7.25, and platinum and standard calomel electrodes were used as the counter and reference electrodes, respectively. (From Ref. 5.)...

See text, bSolid state spectra (Nujol or KBr) unless otherwise stated, only strong bands quoted. cRelative to CD3N02. dRelative to [Mo04]2. e Relative to standard calomel electrode f Petroleum ether solution. e triphos = PhPfCF CHjPPh. h Benzene solution. 1 Toluene solution. 1 Raman spectrum. 

Patterson and Weaver (83) obtained SER spectra of a number of cycloal-kenes, (namely, cyclopentene, cyclohexene, 1,4-cyclohexadiene, and 1,3-cyclohexadiene) on the surface of a roughened gold electrode at potentials between —0.4 and +0.4 V versus the standard calomel electrode. In general, the vC=C modes were reduced in wavenumber, by 65 cm 1 (1,3-cyclohexa-... 

Suppose the reference electrode for Table 12.1 were the standard calomel electrode, Hg2Cl2/Hg,Cl ([Cl] = 1.00 mol L1), with ° set equal to 0. Under this system, what would be the potential for (a) the standard hydrogen electrode (b) the standard Cu2+/Cu redox couple ... 

Suppose that the standard calomel electrode used in Exercise 12.53 was replaced by a saturated calomel electrode (the solution is saturated with KC1). How will this change affect the answers to Exercise 12.53 The solubility of KC1 is 35 g in 100 mL HzO. 

In acetonitrile, the valence band of Ti02 lies at about +2.4 V versus the standard calomel electrode and the conduction band lies at -0.8 V. The hole migrates to the surface where it oxidizes adsorbed olefin (oxidation potential = +1.4 V), producing a surface-bound cation radical. The electron also migrates to the surface where it is captured by adsorbed oxygen (reduction potential = -0.75 V), forming adsorbed superoxide. 

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