Calomel, III

Calcium chloride, III, I, 34, 84, 92 Calcium oxide, IV, S3 Calomel, III, 100 -Caproic acid, IV, 9 Capryl alcohol. (See Methyl hexyl car-binol.)... 

There are few photochemical studies on dinuclear and polynuclear gold (I) and (III) complexes in the literature. The [ n+ l)pa, nda ] excited states of [Au2(dppm)2] are powerful reductants, with an E° value of—1.6(1) V vs. SSCE (saturated sodium chloride calomel electrode) [3, 4a, 9] however [Au2(diphosphine)2] systems do not... 

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. 

Various plutonium materials are dissolved in acidic media and then fumed with sulfuric acid. In a 0.5 M sulfuric acid electrolyte, plutonium is reduced to Pu(III) at a platinum working electrode maintained at 0.310 V relative to a saturated calomel electrode. Plutonium (III) is oxidized to Pu(IV) at 0.670 V for the coulometric measurement. This work supports manufacturing, stock pile reduction, and pilot programs for making nuclear fuels from the stockpile. 

The redox couple (Fe(II)/Fe(III) causes a potential of approximately 450 mV/SCE (saturated calomel electrode). Some of the Cr ions are bound in Fe(III) complexes. Melstrom and Bernhardsson have measured the activity of CF to be 0.53 mole/liter. 

The electrochemical redox potential of several possible decomposition reactions at pH = 0 (relative to the potential of the saturated calomel electrode), which have been estimated from thermodynamic parameters (6,17-21), are shown schematically in Figure A. The band levels are shown for open-circuit conditions. The standard electrode potentials were calculated from the free energies of formation, which are summarized below in Table III. 

Iron (III) chloride Mercury (II) chloride Red coloration due to complex formation White precipitate of calomel produced on warming upon boiling, a black deposit of elemental mercury is produced... 

Both complexes are readily oxidized to the corresponding ion(III) compounds by strong oxidants in acid solution. They can be successfully titrated with cerium(IV) sulfate in sulfuric acid.4 The equivalence point is best detected potentiometrically (Pt vs. calomel electrode). 

In general, to compensate for larger IR drops, a three-electrode setup is used Most of the current I is passed between (i) the working electrode (WE) and (ii) an auxiliary electrode or counter electrode (CE), between which most of the IR drop will occur. The potential is monitored between WE and (iii) a reference electrode (RE), which draws very little current it is most often an NHE, or a standard calomel electrode (Hg Hg2Cl21KC1), or an Ag AgN03 electrode. A hopefully small fraction of the overall internal resistance, known as the "uncompensated" resistance Ru, will still be present between WE and RE the goal is to make Ru/R tolerably small. Figure 6.9 shows the symbols used for three-electrode electrochemical cells. 

Calomel electrode — is an - electrode of the second kind. It was introduced in 1890 by Ostwald, F.W. Asa- reference electrode of fixed, well-known, and very reproducible -+potential, it is still a commonly used reference electrode in electrochemistry [i—iii]. It consists of mercury, sparingly soluble mercurous chloride (calomel), and a chloride-containing solution. The electrode net reaction can be formulated in the following way ... 

If we have a solution in which both iron(II) and iron(III) ions are present, we can construct a half-cell by immersing a platinum foil as an electrode into it, and connecting the platinum electrode to the electrical circuit. The platinum should not be coated with platinum black in this case as we do not want any adsorption to take place on the surface, a so-called bright platinum electrode must therefore be used. With a suitable salt bridge we can connect this solution to another half-cell (e.g. a standard hydrogen or calomel electrode) and the e.m.f. of this cell can be measured. The potential of the half-cell corresponds to the half-cell equilibrium ... 

A number of workers have investigated the electrochemical behavior of the [Mn(terpy)2] cation 6, 61, 256, 330, 377). In acetonitrile solution, there is a well-defined oxidation to the manganese(III) state at -1-1.28 V relative to the standard calomel electrode this species is stable, in contrast to the tris(bipy) and tris(phen) analogues, which are converted to binuclear diman-... 

The hydrogen ion activity of the equilibrium aqueous phase was measured with Beckman pH and saturated calomel electrodes. The reference voltage Ea of the system was calculated using the Nemst Equation and the electrode measurement of standard buffer solutions. For all pH electrode measurements Ea varied only slightly between 414 and 417 mV. The data are shown in Table III and the calculated hydrogen ion activity [H+] is based on the average of the two values of electrode voltage (El and E2). 

Multimetallic sandwiches, including polymetallocenes, bis(fulvalene)-dimetal compounds, multi-decker sandwiches, and compounds in which two metals are bonded to a common unsaturated cyclic hydrocarbon are discussed in Section II. Sections III and IV are subdivided according to the metal group, and describe ligand-bridged bimetallics and metal clusters, respectively. Where appropriate, redox potentials have been included. Unless otherwise stated they are referenced versus the aqueous saturated calomel electrode (see). 

This value, together with the activity coefficient 0.733 for 0.1 normal silver nitrate from Table III, Chapter 8, and the value, page 248, of the potential of the tenth normal calomel cell gives, at 25°... 

Table III. Values of the Constant, eU for the Hydrogen Electrode and of Eg for the Quinhydrone Electrode for use in pH,Determinations at Various Temperatures with the 0.1 Normal Calomel Electrode...

The cyclic voltammetric experiment is an interfacial electrochemical technique (i.e. monitoring of processes occurring near the electrode surface) that involves measurement of current flow as a function of applied potential. The potential is swept from a resting potential, (measured against a reference such as the saturated calomel electrode or the potential of the Fe(II)/Fe(III) couple in ferrocene), at a constant rate (usually... 

An iron alloy or ore is dissolved in HCl and the iron is then reduced from Fe(III) to Fe(n) with stannous chloride (SnCl2). The excess SnCla is oxidized by addition of HgCl2. The calomel formed (insoluble Hg2Cl2) does not react at an appreciable rate with the titrant. The Fe(II) is then titrated with a standard K2Cr207 solution to a diphenylamine sulfonate end point. 

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