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


Redbird Subway Car - in service
Type:
250 "Redbird" subway cars - NYC Subway system - steel bodies / frames
Built:
1959-1960 - American Car & Foundry - Model R26 # 7750-7859
1960-1961 - American Car & Foundry - Model R28 # 7860-7959
1962-1963 - St. Louis Car - Model R29 # 8570-8805
1962-1963 - St. Louis Car - Model R33 # 8806-9345
1963-1964 - St. Louis Car - Model R36 # 9346-9769
Specs:
( 51 x 9 ft ) 15,000 to 18,000 pounds (body)
Sunk:
50 cars - Cape May Reef on July 3, 2003
50 cars - Deepwater Reef on July 16, 2003
50 cars - Atlantic City Reef on July 25, 2003
50 cars - Garden State North Reef on Sept 3, 2003
50 cars - Shark River Reef on Oct 14, 2003
619 cars - Delaware Reef 11 from Aug 2001 to Nov 2003
Sponsor:
New York City Metropolitan Transportation Authority (MTA)
anti-
Sponsor:
Environmental group Clean Ocean Action lobbied aggressively and almost successfully to prevent the use of these subway cars as artificial reefs in New Jersey, resulting in most of the cars going to other states.
GPS:
too many to list, and all gone anyway
Depth:
Depths vary by location between 80 ft and 130 ft.

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