Density & Specific Gravity

Specific gravity is the ratio of the density of a material to the density of water. Materials with a specific gravity greater than 1.000 ( 1.035 in the ocean ) sink; materials with a specific gravity less than 1.000 ( 1.035 in the ocean ) float. Lead has the highest specific gravity - 11.35, except for gold. Gases like air also have weight, density, and specific gravity.

These figures are approximate and should be used only as general indicators.

Material

Density
( lb / cu-ft )

Specific
Gravity

Liquids

Water - pure (@ 39°F)

62.4 1.000 (reference)
Seawater (@ 39°F)

64.1 - 64.9
( 64.6 std )
1.027 - 1.040
( 1.035 std )
Ice (@ 32°F)

56.2 0.90
Petroleum Oil ~ 51.2 ~ 0.92

Seawater varies in salinity from place to place. High evaporation levels cause noticeably saltier surface water in the tropics. Freshwater runoff in some enclosed northern areas like the Baltic Sea dilutes the seawater to almost fresh. Locally, the specific gravity averages about 1.031.

Gases

Air - moist 0.075 0.0012
Air - dry 0.076 0.0012
Air - 500 psi 2.66 0.04201
Air - 3000 psi 15.59 0.2461

Helium

0.0111

0.0002
Nitrogen 0.0781 0.0013
Oxygen 0.0892 0.0014

compressible gases @ 1 Atmosphere ( 14.696 psia ) ~ 32°F
unless otherwise specified

1 cu-ft = 7.48 gallons

Note: a full 80 cubic foot scuba cylinder holds 77 x 0.076 = 5.85 pounds of air.

Metals

Aluminum * 168 2.70
Titanium 283 4.54
Rust ~ 330 ~ 5.3
Iron * 437 - 491 7.00 - 7.87
Steel * 490 7.85
Bronze * 518 8.30
Brass * 524 8.40
Monel * 552 8.8
Copper 559 8.96
Silver 655 10.5
Lead 708 11.35
Uranium 1184 19.0
Gold 1206 19.3

* depends on alloy and/or preparation

Plastics

Styrofoam (uncrushed) ~2.3 ~0.04
Rubber / Neoprene (foam) 8.0 - 12.0 0.13 - 0.19
PE (polyethylene) 58.7 0.95
ABS 65.7 1.05
Nylon 68.7 1.10
Rubber / Neoprene (solid) ~68.7 1.10
PVC (polyvinylchloride) 81.1 1.30
Fiberglass ~124.8 ~2.0


Woods

Softwoods:
Balsa * 6.9 - 8.7 0.11 - 0.14
Cork * 12.5 0.20
White Pine * 17.5 - 26.2 0.28 - 0.42
Cedar * 30.6 - 35.6 0.49 - 0.57
Hardwoods:
Red Oak * 28.1 - 41.8 0.45 - .067
White Ash * 30.0 - 44.9 0.48 - 0.72
Lignum vitae * 80.0 1.28

Wood - waterlogged * (all)

93.6

1.5

* depends on moisture content and other factors

Miscellaneous

Coal ( solid ) 84 - 94 1.3 - 1.5
Limestone ( coral ) 125 2.0
Ceramic 125 2.0
Brick 131 2.1
Concrete 144 2.3
Granite 162 2.6
Glass 162 2.6

Muscle

64.8

1.04
Fat 57.4 0.92
Bone 115.2 1.85
Blood 66.0 1.06 *
Brains ** **

* so blood is thicker than water
** depends on the individual


A tugboat is a small sturdy and powerful vessel designed to push or tow other vessels and barges

Tenacious tugboat
Tenacious

You will see them in every sizable port; smart, businesslike small ships, low in the water and surging out to a large inbound ship. Tugs represent power for pushing and pulling, an engine with just enough hull for adequate buoyancy. Thick fenders for close-quarters work, pushing a big ship alongside the quay against the wind, hauling her off at the end of a towing wire.

Printed from njscuba.net