A Method of Charcoal Analysis

Because of the wide range of production methods for charcoal lumps and briquettes, the quality of the product is not always uniform and consistent with the established levels for general market acceptance. A standard method of analysis is needed. Present methods are based on ASTM methods for coal and coke (D-271-48 and D-346-35), while the method outlined here applies specifically to charcoal. To prepare samples for analysis, select a representative air-dry sample of charcoal and grind it carefully to pass a coarse screen such as a No. 20 U.S. Standard Sieve. Heat generated by excessive grinding will cause loss of moisture and distort the results. Store the ground samples in airtight containers and shake well before testing. Heat a muffle furnace to 750?C and place previously ignited porcelain crucibles (41 milimeters by 37 milimeters) and lids in the furnace for 10 minutes, then cool in a desiccator for 1 hour. Weigh the crucibles and add an accurately weighed (to 1/10 miligram) sample of about 1 gram of charcoal. To determine moisture content, place the samples in the oven at 105?C for 2 hours, cool in a desiccator for 1 hour, and weigh. To determine volatiles, heat the furnace to 950?C and, with the furnace door open, preheat the crucibles containing the samples used for moisture determination on the outer ledge at 300?C for 2 minutes, and on the edge of the furnace at 500?C for 3 minutes. Move the samples to the rear of the furnace, close the door and observe through a peephole; if sparking occurs, results will be in error. Remove the samples, place in a desiccator for 1 hour and weigh. For ash determination, place the same samples in the furnace for 6 hours at 750?C; burn the samples repeatedly until successive 1 hour periods of heating result in a loss of less than 0.0005 gram. Analysis should be carried out on duplicate samples for ash values should agree within 0.1 percent.

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