User:Milton Beychok/Sandbox

Coal classification
There are many compositional differences between the coals mined from different coal deposit locations worldwide. The different types of coal are most usually classified by rank which depends upon the degree of transformation from the original source (i.e., decayed plants) and is therefore a measure of a coal's age. As the process of progressive transformation took place, the heating value and the fixed carbon content of the coal increased and the amount of volatile matter in the coal decreased. The method of ranking coals used in the United States and Canada was developed by the American Society for Testing and Materials (ASTM) and is based on a number of parameters obtained by various prescribed tests:


 * Heating value: The energy released as heat when coal (or any other substance) undergoes complete combustion with oxygen.
 * Volatile matter: The portion of a coal sample which, when heated in the absence of air at prescribed conditions, is liberated as gases. It includes carbon dioxide, organics and inorganic gases containing sulfur and nitrogen.
 * Moisture: The water inherently contained within the coal and existing in the coal in its natural state of deposition. It as measured as the amount of water released when a coal sample is heated at prescribed conditions. It does not include any free water on the surface of the coal. Such free water is removed by by air-drying the coal sample being tested.
 * Ash: The inorganic residue remaining after a coal sample is completely burned and is largely composed of compounds of silica, aluminum, iron, calcium, magnesium and others. The ash may vary considerably from the mineral matter present in the coal (such as clay, quartz, pyrites and gypsum) before being burned.
 * Fixed carbon: The