Dear All,
Does anyone know the history of 'standard' air pressure of 29.92 inches of
mercury (inHg) or 760 millimeters of mercury (mmHg).
When I looked at the values that have been used previously I found:
One atmosphere of pressure is equivalent to:
760 millimeters of mercury
29.92 inches of mercury
14.7 pounds per square inch (psi)
1013.25 millibar (mb)
34 feet of water (approximately 10 meters of water)
Thinking that the 'standard' air pressure might be a mid-point between high
and low pressures, I investigated to find that:
The lowest air pressure recorded at sea level was 87 kilopascals, and
the highest air pressure recorded at sea level was 108.4 kilopascal, but
the mid-point between these values is 97.7�kilopascals, and this doesn't
seem to fit with any of the previously used 'standard' values.
I then thought that 10 metres of water might be a clue. Taking the standard
value of acceleration due to gravity (g) as 9.806�65 metres per second
squared, I found that the pressure below 10 metres of water is about
98�kilopascals, so I had no luck there either.
Can anyone help with the history of 'standard' air pressure?
Thanks,
Pat Naughtin LCAMS
Geelong, Australia
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