Reference electrodes standard calomel electrode

Table la.30 Corrosion properties of the stainless steel X2CrNiMol7133 in 0.9% NaCl. Potential referred to standard calomel electrode (SCE) (Ref. 18)... 

Direct potentiometric method The sample and standard solutions are introduced into the potentiometric measuring cell mixed with background electrolyte. The fluoride ion-selective electrode and appropriate reference electrode (saturated calomel electrode or silver/silver chloride electrode with double jimction is recommended) are dipped into the solution and the electromotive force is measured. An EMF versus log (fluoride ion concentration) calibration curve is used for evaluation. 

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 ... 

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.)...

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.)...

Electrochemical data have been used to predict ionization energies and stability relative to doping in air for semiconducting polymers. Bredas et al. [43] derived an empirical correlation for determination of ionization energies from electrochemical oxidation and reduction potentials (Eq. 5) in which the onset of oxidation is referred to the standard calomel electrode, S.C.E.)... 

Data based on tables in Ref. [2] and references therein values in eV obtained in acetonitrile, H20, or other polar solvents redox potentials are reported vs. standard calomel electrode calculation of AGeI performed with Eq. (13). Abbreviations CA = chloranil CN = 1-cyanonaphthalene bpy = 2,2 -bipyridine, MV2+ = methylviologen dicp = 1,3-diisocya-nopropane and TMB = N,N,iV, N -tetramethylbenzidine... 

A recent study [93JCS(D)967] of aryl-l,3,2,4-dithiadiazoIylium salts has shown that they typically show a half-wave reduction potential in the region +0.29 Em < +0.4 V (with reference to the standard calomel electrode). As found for the 1,2,3,5-isomers, these salts show a Hammett relationship between 1/2 and the a value for the para substituent on the aryl group. The greater reaction constant p, for the 3+/3 redox system, compared with 2+/2, is in agreement with MO calculations—which indicate some unpaired spin density on the heterocyclic carbon, allowing delocalization onto the aryl substituent. (The nodal plane associated with 2 prohibits, to a first-order approximation, delocalization with the aryl functionality.)... 

The other diad system, consisting of sensitizer 1 deposited on Cab-O-Sil and electron donor 3 in solution, shows more interesting photochemistry. Referring to Figure 5, the redox potential of 3 allows for the reductive quenching of excited-state Ru(II) via reaction 2. The formal potential of 3 is +0.50 V versus SCE (standard calomel electrode) in aqueous solution (0.1 M KCl, Pt working electrode) by way of comparison, the formal potential of the Ru-(II)-Ru(I) couple is ca. +0.6 V (97, 98). 

SCE Standard Calomel Electrode A reference electrode based on the... 

Accurate measurement of pH is achieved by the use of electrical pH meters. Potentiometric meters consist of a measuring electrode (hydrogen gas, quinone, glass, or antimony) and a reference electrode or standard electrode (usually calomel) connected to a potentiometer circuit which measures the voltage generated by the electrical cell when the electrodes are immersed in the solution to be tested. These meters... 

The experimental arrangement for the measurement of corrosion potential is shown in Fig. 3.18a. The potential of the metal electrode (working electrode) is measured with respect to a standard Calomel electrode, which is non-polarizable. The reference electrode is kept in a separate container and it is connected electrically with the working electrode placed in a container in contact with the electrolyte via a salt bridge. A high impedance voltmeter is connected between the working electrode and the reference electrode. The negative terminal of the voltmeter is connected to the... 

Linear polarization techniques are often used to conduct an initial electrochemical characterization of a metal or alloy, prior to more complex investigations, torr is first determined relative to a reference eicctrxxle, usually the standard calomel electrode (SCE). A small potential is then applied and swept from about 20 mV below to 20 mV anodic to it. The current density is measured and is calculated. 

Experimentally, the aqueous iron(II) is titrated with cerium(IV) in aqueous solution in a burette. The arrangement is shown in Figure 4.6, the platinum indicator electrode changes its potential (with reference to a calomel half-cell as standard) as the solution is titrated. Figure 4.7 shows the graph of the cell e.m.f. against added cerium(IV). At the equivalence point the amount of the added Ce (aq) is equal to the original amount of Fe (aq) hence the amounts of Ce (aq) and Fe (aq) are also equal. Under these conditions the potential of the electrode in the mixture is ( - - f)/2 this, the equivalence point, occurs at the point indicated. 

The most widely used reference electrode, due to its ease of preparation and constancy of potential, is the calomel electrode. A calomel half-cell is one in which mercury and calomel [mercury(I) chloride] are covered with potassium chloride solution of definite concentration this may be 0.1 M, 1M, or saturated. These electrodes are referred to as the decimolar, the molar and the saturated calomel electrode (S.C.E.) and have the potentials, relative to the standard hydrogen electrode at 25 °C, of 0.3358,0.2824 and 0.2444 volt. Of these electrodes the S.C.E. is most commonly used, largely because of the suppressive effect of saturated potassium chloride solution on liquid junction potentials. However, this electrode suffers from the drawback that its potential varies rapidly with alteration in temperature owing to changes in the solubility of potassium chloride, and restoration of a stable potential may be slow owing to the disturbance of the calomel-potassium chloride equilibrium. The potentials of the decimolar and molar electrodes are less affected by change in temperature and are to be preferred in cases where accurate values of electrode potentials are required. The electrode reaction is... 

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