Comparative Value of Coal to Other Fuels.
—Until a comparatively recent time, coal has been sold by weight and reputation alone; but conditions are rapidly approaching, which will require it to be sold according to its composition and heating value. Among manufacturers and others using large quantities of fuel, the practice of contracting for coal by specification is becoming increasingly common. The determining factors are the amounts of moisture, ash, sulphur, carbon, and volatile matter the coal contains, as well as the size of the pieces and freedom from dust. In a few of the most progressive cities, coal dealers are required to supply coal for schools and other municipal uses, which has been subject to the approval of the City Engineer. The time is not far distant when dealers will be required to submit samples of all fuel, for sale to the public, to the examination of the municipal authorities.
The following table of the heating values of various fuels is taken from Benson’s “Industrial Chemistry.”
British Thermal Units for One Cent from Different Fuels
| Acetylene, from carbide at 10 cents per pound | 600 |
| Denatured alcohol, at 40 cents per gallon | 2,000 |
| Air gas (from gasoline, 80°Bé at 25 cents per gallon) | 3,000 |
| Water gas, at $1 per 1000 cubic feet | 3,000 |
| Coal gas, at $1 per 1000 cubic feet | 6,500 |
| Gasoline, at 20 cents per gallon | 7,500 |
| Kerosene, at 15 cents per gallon | 11,000 |
| Natural gas, at 50 cents per 1000 cubic feet | 18,000 |
| Charcoal, at 10 cents per bushel (15 pounds) | 20,000 |
| Petroleum at 5 cents per gallon | 30,000 |
| Producer gas, from anthracite, $7 per ton | 30,000 |
| Producer gas, from coke, $5 per ton | 36,000 |
| Anthracite, at $7 per ton | 46,000 |
| Producer gas, from soft coal, at $3 per ton | 50,000 |
| Coke, at $5 per ton | 54,000 |
| Mond producer gas from soft coal, at $3 per ton | 65,000 |
| Soft coal, at $3 per ton | 80,000 |