A new procedure for classifying coals is needed. This procedure must recognize both coal type (proportions of various macerals and minerals) and rank (stage of metamorphic development). An integrated program must be instigated to study a large number of vitrinite-rich samples covering a broad range of ranks. Fundamental properties, including molecular structures, must be related to responses of the samples in conversion processes. Properties and responses of liptinite and inertinite, and interactions of inorganics, subsequently must be integrated with the data from vitrinites. Multivariate statistical treatment of the data will be required. Until such a unified classification system is devised, we shall continue to be limited to applying empirical tests to predict process responses, a procedure hardly deserving to be called a science.Coal is a sedimentary rock accumulated as peat, composed principally of macerals and subordinately of minerals, and containing water and gases in submicroscopic pores. Macérais (mas' er-als) are organic sub stances derived from plant tissues, cell contents, and exudates that were variably subjected to decay, incorporated into sedimentary strata, and then altered physically and chemically by natural (geological) processes.Coal is not a uniform mixture of carbon, hydrogen, oxygen, sulfur, and minor proportions of other elements; nor is it, as is often implied, simply a uniform, polyaromatic, polymeric substance.Rather, it is an aggregate of microscopically distinguishable, physically distinctive, and chemically different macérais and minerals.Coal is analogous to a fruitcake, formed initially as a mixture of diverse ingredients, then baked to a product that is visibly heteroge neous. The heterogeneous nature of coal is evident in Figure 1, a
