OT: pints, pounds (Was: APL\360

[Philip Belben]

> 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.