Talk: Density
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Water isn't really defined to have density 1 is it? That's a schoolboy definition. --drj
Mayhaps, I certainly was a schoolboy once :-) The fact that one litre of water weighs exactly one kilogram os no accident however. The SI units were chosen carefully, although i know not if the metre or the kilogram was defined first (my money is on the metre), the relation between them is indeed found through the density of water (at 4 degrees celcius if memory serves correctly). --Anders Törlind.
Oh, by the way, is the kilogram still defined as the lump of platinum they hold in Paris, or is it defined as a certain number of atoms of something? --Anders Törlind
I wondered about this recently. My research confirms what kilogram says. There is a standard mass made from platinum/rhodium. I guess it is too difficult to define it as the number of atoms of something. --drj
I believe that the metere was originally defined to be 1x10-6 of the distance from the equator to the north pole via a line that went through Paris, this was mesured incorrectly at the time, so the distance is somewhat different. The other units as far as I know are based on that. The kilogram was originally based on a cubic decimeter of water, but that is much too variable to be used as a reference.-- mike dill
- Actually, one ten-millionth, which is 10-7. (I fixed your tags.) Vicki Rosenzweig
Do you have the reference for the platinum density of 21.09? According to http://hypertextbook.com/facts/2004/OliviaTai.shtml, the density is 21.45 and they list 5 references. When I Google platinum density, the first entry webelements.com (another wiki) agrees with 21.09, but going on down the list several pages, everyone else says from 21.4 to 21.5. If you change to 21.45 then change the Wikipedia platinum article also. Art LaPella 05:04, Aug 22, 2004 (UTC)
I have checked the CRC Handbook of Chemistry and Physics (60th edition, page B-106) and it gives 21.45 at 20 degC: so have changed here and on the platinum page.
--GPoss 06:36, Aug 22, 2004 (UTC)
