Torr
The torr (symbol Torr ) or millimetre of mercury (symbol mm Hg ) is a measuring unit of the initially definite Pression like the exerted pressure with 0°C by a column of 1 Millimètre of mercury (mmHg).
It later was indexed on the Atmospheric pressure: 1 standard atmosphere corresponds to 760 mm Hg and has 101 325 Pascal S.
One from of thus deduced that the torr is equivalent to approximately 133,322 368 Pa.
An European directive of 1984 defines it directly in term of pascals: 1 mm Hg = 133,322 Pa.
The torr car its name of the Physicist and Italian Mathematician Evangelista Torricelli.
Calculation
One can find by calculation the value of a torr in a PASCAL: it is about the product of the constant of gravity G = 9,81 m/s by the density of mercury rô = 13,6 kg/l.
Within the framework of medicine
This unit of measurement of Pression is used in Médecine under its name " millimetre of mercure" (noted mmHg) to quantify the Blood-pressure although it is more regularly expressed in centimetre of mercury (noted cmHg); 1 cmHg being equal to 10 mmHg.
One also uses it for the intraocular Pression, whose normal values lie between 9 and 21 mmHg.
Within the framework of physics
This unit of Pression is used in physics in the case of the very low pressures (deposit CVD, vacuum application).
External bonds
- Conversion of torr towards other units of pressure
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