THE RELATION BETWEEN VITRAIN PROPERTIES AND THE DEVELOPMENT OF OPTICAL ANISOTROPY DURING CARBONIZATION

Vitrains hand picked from a rank series of British coals were carbonized to various temperatures between 300 and 1000-degrees-C. The semicokes and cokes so produced were subjected to chemical analysis, and determinations of crystallite size by X-ray diffraction, reflectance properties and of optical texture composition by polarized-light microscopy. Consideration of the chemical and physical data in relation to the optical anisotropy showed association between the development of the optical anisotropy and the loss of volatile matter, and between the formation of the different anisotropic entities and different carbon contents. The composition of the parent vitrain is the prime factor controlling the anisotropic texture developed during carbonization, and the changes in the physical properties can be interpreted in terms of increasing molecular order and size as mosaic anisotropy grows in grain size through to flow-type anisotropy.