| http://www.w3.org/ns/prov#value | - Heretofore, in the process of extracting various products or byproducts from carbonaceous material such as coal, it has been necessary to pass the material first through a retort for the purpose of extracting as much moisture as possible from the coal, and then afterwards the coal was passed through another retort, heated to a higher temperature for the actual separation of the various volatile pr
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