Electromotive force description

It is relevant to follow up the description given above on reversible electrodes with attention focused on the potential difference of a cell. The potential difference measured under reversible conditions, is called the electromotive force, or emf, of the cell, E. It is clear that if a cell is reversible then it is implied that the half-cells of which it is composed are also reversible. 

A more complete description of this research will soon appear in the Journal of the American Chemical Society. The preparation of the cells so as to secure constancy and reprodudbility of the electromotive force values, the methods of making the measurements, the full experimental data, and thermodynamic calculations from them of other free-energy values will be there presented in detail. 

Ion-selective electrode theories need to explain why a stable electromotive force (e.m.f.) develops in the measurement cell, how the concentration of the primary ion and interfering ions affect the e.m.f., and how fast the e.m.f. responds to changes in sample composition. The theories are usually based on a model description of the measurement cell and the process occurring in it. Before going into details it should be noted that different, sometimes mutually contradicting models, may equally well explain the same potentio-metric observation. In fact, different real systems may behave potentiometrically in the same way. In other words, potentiometric observations are usually not very useful as positive proof of a model additional information, e.g., from surface spectroscopies, impedance measurements, radiotracer studies, is necessary. 

The transformer to describe coupling of the electromagnetic induction is replaced by following simple description. Namely, when the terminal voltage of the inductance component L in the TMS coil is Vl, the induced electromotive force is driven to the bioelectric measurement system as shown in the Fig. 1, where is a proportional factor. Furthermore, it is assumed that the coupling influence from the bioelectric measurement system to the TMS equipment is negligible, and TMS affects to the human body only in the oscillation mode. 

Electrodialysis is another method of separating ions, a membrane is used that selectively passes anions or cations. The transfer is accomplished by the induction of an electromotive driving force that causes the permeable ions to be transferred across the membrane from a solution of low concentration to one of higher concentration. See references 42, 43, and 44 for the description of equipment and situations where this method is used. 

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