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Thermal Units.

The BRITISH THERMAL UNIT (B. T. U.) is the heat required to raise the temperature of one pound of water, one degree Fahr. (average between 32° and 212°F). As one kilogram is equal to 2.20462 pounds and one degree Cent. is equal to 9/5 degrees Fahr. the large calorie is 3.96832 (2.20462 × 9/5) times as great as the British Thermal Unit, the small calorie being 0.00396832 times the British thermal unit.

The SMALL CALORIE is the amount of heat required to raise the temperature of one gram of water one degree Cent. (from 0° to 1°, 4° to 5°, or 15° to 16° being used, giving slightly different values.)

The LARGE CALORIE is the amount of heat required to raise the temperature of one kilogram of water one degree Cent. It is therefore one thousand times as large as the small calorie.

The HEAT OF COMBUSTION of a substance is the number of small or large calories of heat evolved during the combustion of a gram or a kilogram of the substance.

Using the English weights and measures, it is the number of B.T.U. of heat evolved during the combustion of one pound of the substance. To convert the former into the latter value the number of calories must be multiplied by 1.8 (3.96832 ÷ 2.20462).

The HEAT OF FORMATION of a substance is the number of calories of heat evolved or absorbed when a gram molecular weight of the substance is formed. When heat is absorbed, the value found is negative.

The MELTING POINT of the substance is the temperature at which the solid or liquid forms are capable of existing together in equilibrium.

The BOILING POINT of a liquid is the highest temperature at which the liquid and its pure vapor can exist together in equilibrium. This temperature varies with the pressure.

The SPECIFIC HEAT of a substance is the ratio of the number of thermal units necessary to raise the temperature of a substance one degree, divided by the number of thermal units necessary to raise the same weight of water at 60°F one degree. It may also be defined as the number of thermal units required to raise the temperature of one gram of a substance one degree Centigrade.

The HEAT OF FUSION of a substance is the number of thermal units required to change a unit mass of the solid at its melting point into liquid at the same temperature.

The HEAT OF VAPORIZATION of a liquid is the number of thermal units required to change a unit mass of the liquid at its boiling point into vapor at the same temperature.

TEMPERATURE UNIT or thermal intensity is measured in degrees Centigrade (Celsius) or degrees Fahrenheit. One degree Cent. is one one-hundredth of the difference of temperature between the freezing point of water and its boiling point at 760 millimeters pressure as indicated by the expansion of mercury. A degree Fahr. is one one-hundred eightieth of the difference of temperature between the freezing point of water and the boiling point of water.

MECHANICAL EQUIVALENT OF HEAT-779.4 ft. pounds 1

B.T.U.

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45 50 55 60 65 70 75 80 85 90 95 100 PER CENT DISTILLED

Fig. 72-Shale Oil Fractional Gravity Before and After Cracking.

Distillation Products of Coal and Oil Shale.

Oil shale is a stratified sedimentary rock in which are found numerous fragments of fossil plants and animals, principally aquatic form. Oil shale in its natural form does not contain any oil whatever but it does contain on the average about 35% of organic matter. The mineral base of oil shale presents a suggestion as to the origin of the organic matter. The mineral is a hydrous silicate of alumina and as a general rule hydrous silicates of alumina have great absorptive power for hydrocarbons of large molecular weight. A typical one, Bentonite, as well as Fuller's Earth, has the property of decolorizing and removing complex matter from hydrocarbon oils. Oil shale may then be compared with Fuller's Earth which has turned black or greenish black after absorbing a large amount of coloring matter from petroleum. This may readily have taken place while the petroleum was vaporizing. This organic matter when subjected to pyrogenic distillation forms the following products:

Fuel oil or shale oil, 20.25% equal to 405 lbs. or 54 gal. per ton.
Water, 4.08% equal to 83 lbs. or 10 gal.

Combustible gas 8.86% equal to 1,605 cubic cubic feet.

Ammonia as ammonium sulphate, 0.90% = 34 lbs. ammonium sulphate.

Mineral matter and carbonaceous residue 66.0%.

With a low temperature distillation, larger amounts of heavier fuel oil are obtained. With the higher temperature distillation, smaller amounts of shale oil containing more or less naphtha and burning oil are obtained.

A typical distillation of oil shale is as follows:

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This product in many respects resembles ordinary crude petroleum and for this reason the shale oil industry has aroused great interest on account of its possible substitution for petroleum. Shale oil, however, is utilized in only a few countries, chiefly Scotland, though oil shale is very widely distributed throughout the world. The oil shale resources of the United States are so extensive as to furnish an effective guarantee for the future when the underground reservoirs of petroleum are exhausted. The cost of obtaining the

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