Machinery's Handbook, 31st Edition
Specific Gravity
377
Properties of Mass and Weight Density.— The density of any solid, fluid or gaseous substance is the mass of that sub stance per unit volume. If weight is used in the ordinary sense as being equivalent to mass, then density may be defined as the weight per unit volume. The density depends upon the unit in which the mass or weight is expressed, and upon the unit of volume used. In engi neering and scientific work, density is generally expressed in grams per cubic centimeter, without naming the units, because the density will be equal to the specific gravity. Specific Gravity.— Specific gravity is a number indicating how many times a volume of material is heavier than an equal volume of water. Density of water varies slightly at different temperatures. In exacting scientific studies, a reference temperature of 4 ° C (39.2 ° F) is often used, and the weight of 1 cubic meter of pure water at 4 ° C is 1000 kg. In engineering practice, the usual custom is to measure specific gravity at water temperature of 60 or 62 ° F (15.5 or 16.6 ° C); 1 cubic foot of pure water at 62 ° F weighs 62.355 pounds. Given Rule to find density Given Rule to find specific gravity
weight/cm 3 = S.G. weight/m 3 = S.G. 3 1000 weight/in 3 = S.G. 3 0.0361 weight/ft 3 = S.G. 4 0.01604
weight/cm 3 weight/m 3 weight/in 3 weight/ft 3
S.G. = weight/cm 3 S.G. = weight/m 3 4 1000 S.G. = weight/in 3 4 0.0361
Specific Gravity (S.G.)
S.G. = weight/ft 3 3 0.01604 When specific gravity is known, the weight per cubic centimeter is equal to its specific gravity. The weight per cubic meter equals the specific gravity 3 1000. The weight per cubic inch equals the specific gravity 3 0.0361. The weight of a cubic foot equals the specific gravity divided by 0.01604. When weight per cubic centimeter is known, the specific gravity is equal to the weight per cubic centimeter. If weight per cubic meter is known, the specific gravity equals this weight divided by 1000. If density is given in lb/in 3 , specific gravity may be determined by dividing the density by 0.0361. If weight per cubic foot is known, specific gravity equals this weight multiplied by 0.01604. Examples: The specific gravity of cast iron is 7.2. The weight of 80 cm 3 of cast iron = 7.2 3 80 = 5.6 kg. The weight of 5 in 3 of cast iron = 7.2 3 0.0361 3 5 = 1.2996 pounds. Examples: The weight of a cubic centimeter of gold is 19.31 grams. The specific gravity of gold = weight of a cubic centimeter of gold = 19.31. A cubic inch of gold weighs 0.697 pound. The specific gravity of gold = 0.697 0.0361 = 19.31 Table 15. Average Specific Gravity of Various Substances
a Weight
a Weight
a Weight
Substance
Substance
Substance
ABS
1.05 66 1057 Glass 1.19 74 1185 Glass, crushed 2.6 160 2563 Gold, pure 2.7 167 2675 Granite 2.4 150 2403 Gravel 1.4 87 1394 Gypsum 1.8 112 1794 Ice 1.8 112 1794 Iron, cast 2.3 143 2291 Iron, wrought 2.0 125 2002 Iron slag 2.2 137 2195 Lead 1.55 97 1554 Masonry 2.3 143 2291 Mica 0.4 25 400 Mortar 1.5 94 1506 Nickel, cast 1.3 81 1297 Nickel, rolled 2.2 137 2195 Nylon 6, Cast … 75 1201 PTFE … 100 1602 Phosphorus 4.0 249 3989 Plaster of Paris
2.6 162 2595 Platinum 21.5 1342 21497
Acrylic
… 74 1185 Polycarbonate 1.19 74 19.3 1204 19286 Polypropylene 0.91 57
1185 961 913 1057 2595 769 1602 2002 2291 2803 2691 7865 2002 1201 1794 2995 7320 6872 7208
Aluminum bronze Aluminum, cast Aluminum, wrought
7.8 486 7785 Gold, 22 carat fine 17.5 1091 17476 Polyethylene
0.97 60 1.05 66 2.6 162 … 100 … 125 2.3 143 2.8 175 2.7 168 7.9 491 2.0 125 1.8 112 3.0 187 7.3 457 6.9 429 7.2 450
2.7 168 2691 Polyurethane … 109 1746 Quartz 0.9 56 897 Sand, dry 7.2 447 7160 Sand, wet 7.7 479 7673 Sandstone 2.7 168 2691 Silver 11.4 711 11389 Slate 2.6 162 2595 Soapstone 2.7 168 2691 Steel 2.4 150 2403 Sulfur 2.8 175 2803 Tile 1.5 94 1506 Trap rock 1.16 73 1169 White metal 2.19 137 2195 Zinc, cast 1.8 112 1794 Zinc, sheet
Asbestos Asphaltum
2.4 150 2403 Salt, common … 48
Borax
Brick, common Brick, fire Brick, hard Brick, pressed
10.5 656 10508
Brickwork, in cement 1.8 112 1794 Limestone Brickwork, in mortar 1.6 100 1602 Marble Cement, Portland (set) 3.1 193 3092 Mercury
CPVC Chalk
13.56 845.3 13540 Tar, bituminous 1.2 75
Charcoal
Coal, anthracite Coal, bituminous Concrete Earth, loose Earth, rammed
8.3 517 8282 Water at 4 ° C 1.0 62.43 1000
8.7 542 8682 Water at 62 ° F 1.0 62.355
Emery
1.8 112 1794
… … … …
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