This part of ISO 7404 specifies the method for determining the reflectance of vitrinite of coals microcopically on the polished surfaces, immersed in oil. The methods are applicable to coals from single seams or coal blends covering the whole range of low, medium and high rank coal.Vitrinite reflectance measurements can be used to characterise the components within blends. Measures can be taken to correct for the vitrinite percentage within each of the components of the blend or determining the proportion of components in a blend, particularly when the components have dissimilar vitrinite contents. The method necessitates the identification of vitrinite by