Specific Gravity

Specific gravity is a number indicating how many times a certain volume of a material is heavier than an equal volume of water. The density of water differs slightly at different temperatures, so the usual custom is to make comparisons on the basis that the water has a temperature of 62°F. The weight of 1 cubic inch of pure water at 62°F is 0.0361 pound. If the specific gravity of any material is known, the weight of a cubic inch of the material, therefore, can be found by multiplying its specific gravity by 0.0361.

Example:The specific gravity of cast iron is 7.2. Find the weight of 5 cubic inches of cast iron.
7.2 × 0.0361 × 5 = 1.2996 pounds
To find the weight per cubic foot of a material, multiply the specific gravity by 62.355. If the weight of a cubic inch of a material is known, the specific gravity is found by dividing the weight per cubic inch by 0.0361.

Example:The weight of a cubic inch of gold is 0.697 pound. Find the specific gravity.
0.697 ÷ 0.0361 = 19.31
If the weight per cubic foot of a material is known, the specific gravity is found by multiplying this weight by 0.01604.

The weight per cubic foot is calculated on the basis of the specific gravity except for those substances that occur in bulk, heaped, or loose form. In these instances, only the weights per cubic foot are given because the voids present in representative samples make the values of the specific gravities
inaccurate.

Average Weights and Volumes of Fuels.—The average weight of a bushel of charcoal is
20 pounds; of a bushel of coke, 40 pounds; of a bushel of anthracite coal, 67 pounds; and of
a bushel of bituminous coal, 60 pounds.
Anthracite coal, 1 cubic foot = 55 to 65 pounds.
Anthracite coal, 1 ton (2240 pounds) = 34 to 41 cubic feet.
Bituminous coal, 1 cubic foot = 50 to 55 pounds.
Bituminous coal, 1 ton (2240 pounds) = 41 to 45 cubic feet.
Charcoal, 1 cubic foot = 18 to 18.5 pounds.
Charcoal, 1 ton (2240 pounds) = 120 to 124 cubic feet.
Coke, 1 cubic foot = 28 pounds.
Coke, 1 ton (2240 pounds) = 80 cubic feet.

Weight of Wood—The weight of seasoned wood per cord is approximately as follows,
assuming about 70 cubic feet of solid wood per cord: beech, 3300 pounds; chestnut, 2600 pounds; elm, 2900 pounds; maple, 3100 pounds; poplar, 2200 pounds; white pine, 2200 pounds; red oak, 3300 pounds; white oak, 3500 pounds.
Weight per Foot of Wood, Board Measure.—The following is the weight in pounds of
various kinds of woods, commercially known as dry timber, per foot board measure: white oak, 4.16; white pine, 1.98; Douglas fir, 2.65; short-leaf yellow pine, 2.65; red pine, 2.60; hemlock, 2.08; spruce, 2.08; cypress, 2.39; cedar, 1.93; chestnut, 3.43; Georgia yellow pine, 3.17; California spruce, 2.08.