OT: pints, pounds (Was: APL\360
Philip Belben
philip at axeside.co.uk
Tue Feb 9 12:07:04 CST 2021
> 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.
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