compression of water--density diff? w/ depth

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compression of water--density diff? w/ depth

Postby Guest » Sat Apr 23, 2005 6:31 am

I was told that water is not compressable.
Does not the density of ocean water increase as depth increases? If it does could I please get a chart and/or be directed to one.

Postby Guest » Sun Apr 24, 2005 12:43 am

Liquids are pretty damn incompressible. I did find a table in an old Handbook of Chemistry and Physics. It gives coefficients for volume change according to relationship

(V1 - V2)/V1 = Xt * (P2 - P1), where the "1" subscript is volume at atmospheric pressure. Note that the volume change is fractional. The table is given in dynes per square centimeter for units, but converting to Pascals:

For water at 0 degrees C, Xt = 5.04E-12 /Pa and
at 10 degrees C, 4.78e-12 /Pa., so at 1 MPa, volume change is about 5 ppm, and density would change by the same amount (opposite sign). You would make a greater error in the assumptions for temperature in the water column overhead.

Usually, deep sea water will be near max. density at 4 degrees C, unless there are thermal vents, etc.

At very high pressures, Xt is not constant, it varies as
Xt = C / ( L + P), for water, C is constant 0.1368, and L is a weak funtion of temperature, 272 Mpa at 0 degrees, 286 MPa at 10 degrees C, and it becomes less compressible than expected at very high pressure.

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