On 01/02/2021 20:07, Fred Cisin via cctalk wrote:
A US pint of water weighs 1.043 pounds.
One "fluid ounce" (volume) of water weighs 1.043 ounces (weight)!
The nit-picker in me would say "you mean mass", except that there's an
even bigger nit to pick - the density of water is not constant but
varies with temperature!
<grin> That's also a US measure. An imperial fluid ounce is 28.4ml and
a floz of water weighs 28.4g, same as an avoirdupois ounce. In fact
it's defined (or was) as the volume of water that weighs one ounce.
The volume that weighs one ounce at what temperature? I think it may be
4°C - the temperature of maximum density.
I often wondered why the US fluid ounce wasn't the same size as ours. I
always assumed that it was measured at a different temperature, until
someone said it was from a different definition of the ounce - not
avoirdupois, but one of the other systems.
The other day I looked up to see whether the density (assuming one ounce
avdp) corresponded to a temperature that made sense, and it turns out it
corresponds to water at 100°C. Not that my data tables gave a density
for water at 100 degrees - but you can extend the line and there it is.
I have no idea whether that is how the unit is derived. The
definition is in terms of cubic inches, which doesn't help settle the
question.
Philip.
