Molar napierian absorption coefficient

In Chapter 3 Napierian units were used for absorption coefficients and absorbance. The reason was a simpler handling of the equations. Since instrumentation reads decadic units, they are used in most equations in this chapter. The decadic molar spectral absorption coefficient e of the compounds (i) varies with wavelength A. For this reason Bouguer-Lambert-Beer s law is restricted to monochromatic radiation. This restriction and the interactions between molecules in concentrated solutions cause two problems in applying the law to quantitative evaluation ... 

In this relationship k, is named the Napierian (natural) molar absorption coefficient [1 mol" cm ] of reactant Aj at wavelength of irradiation. In principle the derivation of the kinetic equations becomes easier if exponential functions and Napierian logarithms are involved. For this reason the Napierian units are used first. Division of the relationship above by the volume of the chosen volume element results in... 

In the course of this formal deduction of the amount of light absorbed, the Napierian molar absorption coefficient k is used. Later in the experimental section and during the practical examples using absorbance measurements, e symbolises the decadic (molar) absorption coefficients obtained in calibration experiments using UV/vis spectrometers. 

Derivation of photochemical equations can become easier using the Napierian molar absorption coefficient. This is discussed in detail in Section 5.1.2.2. The result is the photokinetic factor given by... 

In formal kinetics the symbols A, B,... are used for the reactants. The symbol E is used to represent absorbance in this book. Napierian units are used in this chapter (see Section 1.4.3). In Chapters 4 and 5 decadic units are used for convenience and the decadic molar absorption coefficient is indicated by B as used in Section 1.4.4. 

The physical meaning of the quantities Z(A) and s(A) for a given molarity of solute is as follows the reciprocal of the Napierian coefficient of absorption a(A) corresponds to the thickness of the medium for which the incident intensity is divided by the base of the Napierian logarithm (i.e., e = 2.718281828...), while the reciprocal of the decadic coefficient of absorption e(A) corresponds to the thickness of the solution for which the incident intensity is divided by ten. In addition, note that in analytical chemistry, the solution is in a rectangular cell with optical path denoted I, expressed in centimeters, while the molarity of the solute is expressed in mol.dm hence in this particular case the molar extinction coefficient is expressed in mor. dmlcm . Moreover, in some textbooks (e.g., pharmacy), a derived quantity called the specific molar extinction coefficient, denoted E is defined for a mass concentration of solute of 1 wt.% and a cell having an optical path 1 cm in length. 

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