Refractive index (RI) is the most important optical property of non-opaque materials. It is the leading diagnostic optical property of non-opaque materials, especially asbestos minerals. Dispersion staining (DS) has been proven to be the most effective technique with desirable accuracy for the measurement of asbestos minerals’ RI using the immersion method by polarized light microscopy (PLM). This paper presents a practical procedure for this measurement. To facilitate the analysis, two comprehensive suites of pre-calculated look-up tables for the conversion of the observed matching wavelength to RI were constructed for the two major types of RI liquids: Cargille Laboratories (Cargille) and Delaware Research Institute of Microscopy and Material Characterization LLC (DRIMMC), respectively, covering the range of RI liquids suitable for analyzing the six regulated asbestos minerals. RI liquid calibration in the absence of an Abbe refractometer is discussed. An alternative solution using Cargille optical glass standards is proposed, and two comprehensive suites of pre-calculated look-up tables for both Cargille and DRIMMC liquids are included, covering the range of RI liquids routinely used in the analysis of the six regulated asbestos minerals.
CORRECTIONS: On page 59 of the published article, the Figure 7 illustration is an error and does not depict the “light path of the phase contrast microscope,” as stated in the caption. It is the light path of a darkfield microscope.
On page 63 of the published article, the temperature ranges are incorrect for Table 5. λm and t to RI Conversion for Chrysotile in Cargille 1.550 (E). The correct temperature ranges are 17° to 29° C. Download/view the PDF of the corrected Table 5
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