Moisture As A Component Of The Volatile Matter Of Coal

IN PREVIOUS classifications of coal, it has been customary to regard moisture eliminated from coal samples between 20° and 100° C. as extraneous matter, rather than as a constituent part of the coal. It seems, however, that the physical character and use properties of the low-rank coals are directly related to the amount of such moisture present, and recent chemical work has shown1 that such coals contain unstable groupings which decompose between 20° C. and temperatures somewhat above 100° C., with the splitting off of moisture. According to this view, the moisture eliminated from air-dried coal below boiling point is similar in all essential respects to moisture eliminated above 100° C., and is produced by analogous reactions; and inasmuch as the moisture given off above 100° C. has always been treated as a constituent of the volatile matter of coal, it would seem that consistent usage would include as a part of the volatile matter all moisture present as an essential component of the coal as it occurs in nature. As a matter of experience, it seems clear that the general physical and chemical characteristics of the low-rank coals are largely determined by or related to the moisture, whether chemically or physically combined, present in air-dried coal; it is also demonstrable by trial that the low-rank coals cannot be satisfactorily classified on a purely chemical basis by using the moisture free form of analysis. The low-rank coals of the western United States include numerous well-defined types, many of which were referred to in a classification proposed by Ashley,2 in which the physical and use properties of the coals were made the primary basis for their systematic grouping. When testing this classification by replotting analyses of these type coals according to the Seyler scheme of classification,3 a satisfactory parallelism between use properties and chemical constitution of the dry coal was found among