Slope factor, Nernst equation

The Nernst factor, 0.059 V for room temperature, does not always reach its theoretical value. In experimental work, it is better to use the expression Nernstian slope S of the function E = f(a). The slope must be determined empirically. The constant const in Eq. (7.8) is a combination of all terms not dependent on concentration. In practical work, the name asymmetry potential ( as) is preferred. This expression is derived from the expectation that the constant should be zero for a completely symmetric cell, i.e. if inner and outer solutions are of equal pH and if inner and outer reference electrodes are of identical types. In practice, Eas is not always zero but must be calibrated empirically by means of buffer solutions with known pH. By setting - log alHsO" ) = pH, the common form of the Nernst equation for the glass electrode results ... 

Nernst factor (5, slope) The term 23RTInF is the Nernst equation, which is equal (at T = 25°C) to 59.16 mV when n = 1 and 29.58 mV when n = 2, and which includes the sign of the charge on the ion in the term n. The Nernst factor varies with temperature. (See Table A.l.)... 

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