Weights and measures

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dyqik
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Re: Weights and measures

Post by dyqik » Sat Sep 18, 2021 10:04 pm

Martin_B wrote:
Sat Sep 18, 2021 12:44 am
dyqik wrote:
Fri Sep 17, 2021 3:01 pm
It's important to note that US standard units aren't the same as UK imperial measures, so there's no real advantage for trade with the US for anything requiring precision.

And then there's the measures with the same name that aren't even close. Remember, "a pint's a pound the world round" is a common saying in the US.
To the rest of the world (or at least those parts which use it) a pint is 568 ml. Although asking for a pint in France will get you a drink measured at 500 ml (which I've tried asking for as a demi-litre and got blank looks!)

But a US pint isn't even a pound. A US pint is 473 ml, while a pound is 454 g. For a pint to be a pound the liquid being measured has to be 960 kg/m3. For this to be water (which is a reasonable thing to expect) the water would have to be at ~95°C. At room temperature (20°C) water has a density of 998 kg/m3, so a pint is 1.04 pounds.

It's always possible that the US saying references some other liquid, but beer has a density at room temperature of 1040-1070 kg/m3 (depends on the alcohol content) and milk is 1025-1035 kg/m3 (depending on fat content). Gasoline has a density of 720-780 kg/m3, kerosene 780-830 and diesel 830-850 kg/m3.
You can get a specific grade of very heavy fuel oil which has a density of ~960 kg/m3 at room temperature, but I'm not sure why a common US saying should reference a fairly recently specified, highly specific fuel oil.
Apparently the US fluid ounce is based on the density of wine (and the US pint is based on the wine gallon). 0.960 g/cm³ is pretty low density for wine, but a final gravity of 0.990 relative to water's 1.000 is common for dry white wine. The US and UK used different standard temperatures for the measurement as well.

Btw, beer typically starts at 1.040 to 1.070, and finishes between 1.005 and 1.010 for ales, and as low as 0.995 for saison or light lager.

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