Principles and Techniques of Diffuse‐Reflectance Spectroscopy

Abstract The prerequisites for applicability of the Kubelka‐Munk theory of diffuse reflectance for obtaining characteristic color curves of powders are discussed, and some experimental support for the theory is given. Methods are described for eliminating surface reflection, which is always superimposed upon the diffuse reflection and which therefore distorts the spectrum. The effect of interactions with the adsorbent on the reflection spectra of adsorbed molecules is demonstrated by means of examples, and the special suitability of the method for investigating chemisorption and for following reactions at phase boundaries is pointed out. By analogy to the Beer‐Lambert law, the Kubelka‐Munk function can be used for quantitative photometric analysis. The reflectance curves of white standards are presented, and measurements relating to the conditions for “infinitely thick layers” are reported. The scattering coefficient of the Kubelka‐Munk functions has been estimated for several samples of color‐filters as a functions of grain‐size and wavelength. The effect of moisture on diffuse reflectance spectra is discussed, and details of the measuring techniques are presented.

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