Refractive index of organic compounds

Katritzky, A.R., Sild, S. and Karelson, M. (1998b) General quantitative structure-property relationship treatment of the refractive index of organic compounds./. Chem. Inf. Comput. Sci, 38, 840-844. 

As implied by Eq. 15.2, all the materials in Table 15.1 must have higher refractive indices than the material with which they are in contact. Materials that are commonly used as windows in the mid-infrared [e.g., KBr n = 1.53) and KCl ( i = 1.45)] are not included in this list, as their refractive indices are too low for use as IREs. Because the refractive indices of KBr and KCl are roughly equal to the refractive index of organic compounds, total internal reflection will not be observed. In this case, radiation passes directly through the IRE and sample without regard to the angle of incidence. In other words, these materials are better suited for use as infrared-transmitting windows than as internal reflection elements. 

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