American conventions

The signs of the current refer to the American convention that reduction currents are positive, whereas oxidation currents are negative (remember that in electrochemistry the signs are conventional). 

The potential/current signs in the IUPAC convention follows the criterium positive currents for processes occurring at positive potentials , and vice versa. The American convention still adopts the opposite criterium positive currents for processes occurring at negative potentials , and vice versa. Even if the present theoretical treatment follows the American convention (positive sign to reduction processes), in presenting cyclic voltammetric profiles the IUPAC recommendation will be adopted. 

Solvent displacement, and isotherms. 954. 955 Solvent excess entropy at the interface, 912 Solvent interactions, 923, 964 Soriaga, M., 1103, 1146 Specifically adsorbed ions, 886 Spectrometer, 797 Spikes, electrodeposition. 1336 Spillover electrons, of metal, 889 Spiral growth, electrodeposition, 1316, 1324, 1326, 1324,1328 s-polarized light, 802 Srinivasan, S 1439,1494 Standard electrode potential American convention, 1354 convention, 1351 rUPAC convention, 1355 prediction of reactions, 1359 the zinc-minus and copper-plus convention, 1352... 

In the past the electrostatic convention has often been called the European convention and the thermodynamic convention popularized by Luitmer (The Oxidation Potentials of the Elements and Their Values in Aqueous Solution Prenlicc-HBlI Englewood Cliffs. NJ, (952) the American convention. In an effort to reduce confusion, the IUPAC adopted the "Stockholm convention" in which electrode potentials refer to the electrostatic potential and end s refer to the thermodynamic quantity. Furthermore, the recommendation is that standard reduction potentials be listed as electrode potentials" to avoid the possibility of confusion over signs. 

The American convention would assign a positive value to E° for the Zn Zn2+(aq) half cell written as an oxidation, but a negative sign if written as a reduction. It is seen that the European convention refers to the invariant electrostatic potential of the electrode with respect to the SHE, whereas the American convention relates to the thermodynamic Gibbs free energy which is sensitive to the direction of the cell reaction. 

IUPAC recommends that electrode potential be reserved for the European convention, whereas the EMF of a half cell is dealt with via the American convention. 

Yuan, Y., Gretze, U. and Fesenmaier, D.R. (2003) Internet technology use by American convention and visitors bureaus. Journal of Travel Research 41 (3), 240-255. 

The absorptivity is a fundamental property of a molecule at a specified monochromatic wavelength. It has two connotations in European usage, and a third according to American convention. If the concentration is expressed in mol/litre, then k is described as the molar absorptivity (e, litre/moFcm), and defined as The absorbance of a one molar solution in a cell of 1 cm path-length . It may also be quoted as the logarithm (base 10), the values being in the range 1 to 5. 

When concentration is expressed in g/100 ml, k is described as the specific absorbance and given the symbol A cm or A(l%, 1 cm), defined as The absorbance of a 1% w/v solution in a cell of 1 cm path-length . It is usually written in the shortened form Ai and is widely used in analytical chemistry. It was formerly known as the specific extinction coefficient , symbol or E (1%, 1 cm). American convention recognises the constant k as absorptivity (a, litre/g/cm) defined as the absorbance of a 1 g/litre solution in a cell of 1 cm path-length . These terms for absorptivity can be readily inter-converted, as follows... 

Each convention is unobjectionable if used consistently but the two cannot be mixed because the termination rate constants quoted according to the American convention will be exactly half those measured by the British system. The same conclusions are reached when either usage is adopted because a compensating factor of 2 is present in the kinetic equations that use American rate constants and is absent in the corresponding British system. 

On the other hand, the American convention, which is followed in this text, uses the following definitions ... 

From Eq. (6.15) Rt = 2kt M f = 2 ktc + ktd)[M°f (6.19) where [M ] is the total concentration of chain radicals of all sizes. A factor of 2 is used in the above expressions, in accordance with the generally accepted American convention, since for each incidence of a termination reaction, two chain radicals disappear from the system. Recall that a factor of 2 has also been usd previously in Eq. (6.9) for formation of radicals in pairs. It may be noted that in the British convention, this factor of 2 is not used, both in initiation and termination. However, both conventions are nonobjectionable and they lead to the same conclusions about polymerization rates, but the two cannot be mixed. 

For electrochemical processes we shall use the conventions recommended by the International Union of Pure and Applied Chemistry (IUPAC). Because these differ, often confusingly, from the Latimer or American convention still found in many publications in the USA, a detailed explanation of the International system is provided on pages 164-165. 

Although the electromotive force e is a scalar quantity, it has direction. The American convention is that, at equilibrium, e is given by... 

Convention of signs. In the above examples the standard American convention set by Lewis and Randall has been used. That is, the electrode potential is considered positive if the standard hydrogen electrode in a completed cell... 

Alternative spellings A number of words have more than one spelling. Often in English this is related to American vs non-American conventions so that we have tyre and tire and honour and honor. In many cases these differences are systematic, for instance with the suffix -ISE which can be encoded as organise or organize. Often it is possible to list... 

M. Meselson, Statement included in Hearing on the Biological Weapons Act of 1989 Inter-American Convention on International Commercial Arbitration before the Subcommittee on Immigration, Refugees, and International... 

The reverse method, oxidation potentials (the American convention) is seen in many books and is used by some practicing chemists in their publications. Vigilance is required tn deduce what is meant by electrode potential without the qualifying terms, reduction, oxidation, or lUPAC convention, etc. Careful attention to directions and signs, holding to one consistent form of the Nernst equation, is recommended to avoid sign mistakes in calculations. 

The American convention is followed in this text. In this case ktc and are defined by... 

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