[SciPy-dev] Add density of water to constants?

Pauli Virtanen pav@iki...
Thu Oct 2 13:17:43 CDT 2008


Thu, 02 Oct 2008 12:08:10 -0500, Ryan May wrote:
> I was just cleaning up my own hand-rolled constants file and noticed
> that the only one not already in scipy's own constants file was the
> density of liquid water.  I'm not sure how much we want to accumulate
> more of these physical constants in there, but here's a patch
> nonetheless.

I'm not sure if the density of liquid water is actually a good constant.

First, it varies between 999.972 and 992.2 kg/m^3 already at temperatures 
between 0 °C and 40 °C.

Second, the kilogram is not defined in terms of the density of water, but 
in terms of a metal prototype weight that was manufactured based on a 
single measurement of the density of water. The maximum density of water 
turns out to be, funnily enough, not 1000 kg/m^3 but slightly less. [1,2]

.. [1] "Water". Wikipedia, http://en.wikipedia.org/wiki/H2O
.. [2] "Kilogram. Wikipedia, http://en.wikipedia.org/wiki/Kilogram

-- 
Pauli Virtanen



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