Centerfold. Coal byproducts in tree form showing basic chemicals as branches and derivative substances as twigs and leaves. The basic chemicals may be obtained from coal through heating in a closed container (destructive distillation); the derivatives require additional processing of those basic materials. One ton of bituminous coal roasted in an airtight oven (destructive distillation) produces approximately 1,300 to 1,500 pounds of coke, 8 to 10 gallons of coal tar, 3 gallons of light oil, 5 to 6 pounds of ammonia, and 9,500 to 11,000 cubic feet of gas. Modified from an undated public domain illustration provided by the Virginia Surface Mining and Reclamation Association, Inc. Norton, Va.