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The relationship between the torr and the millimeter of mercury is: 1 Torr = 0.999 999 857 533 699... mmHg; 1 mmHg = 1.000 000 142 466 321... Torr; The difference between one millimeter of mercury and one torr, as well as between one atmosphere (101.325 kPa) and 760 mmHg (101.3250144354 kPa), is less than one part in seven million (or less than ...
Torricelli concluded that the mercury fluid in the tube is aided by the atmospheric pressure that is present on the surface of mercury fluid on the dish. He also stated that the changes of liquid level from day to day are caused by the variation of atmospheric pressure. The empty space in the tube is called the Torricellian vacuum. [3] 760 mmHg ...
1 mmHg = 1 mm × 13 595.1 kg/m 3 × 9.806 65 m/s 2 = 133.322 387 415 Pa (exactly) The use of an actual column of mercury for precise measurement of pressure requires corrections for the actual gravity at given location (±0.44%) and the density of mercury at the actual temperature (−0.45% at 25 °C or 77 °F).
For nearly all intents and purposes, torr is the same as mmHg. However, in most scientific journals, torr usually refers to mmHg (Absolute), (ie: 0 torr = total vacuum), whereas mmHg refers to non-absolute readings, (ie: 0 mmHg = air pressure = 760 torr. Likewise, total vacuum = -760 mmHg). So, 120/80 mmHg will usually equal 880/840 torr .
So, for example, pressure head might be written "742.2 mm Hg" or "4.2 in H 2 O at 59 °F" for measurements taken with mercury or water as the manometric fluid respectively. The word "gauge" or "vacuum" may be added to such a measurement to distinguish between a pressure above or below the atmospheric pressure.
The tube is sealed during manufacture with the sealed end containing a vacuum. [1] Mercury is a useful material to use in a manometer because of its high density. This means that a much shorter column is needed compared to water. [2] For instance, the pressure represented by a column of 100 mm of water is just under 7.4 mm of mercury . [3]
Molecular distillation is vacuum distillation below the pressure of 0.01 torr [21] (1.3 Pa). 0.01 torr is one order of magnitude above high vacuum, where fluids are in the free molecular flow regime, i.e. the mean free path of molecules is comparable to the size of the equipment. [1]
McLeod gauges operate by taking in a sample volume of gas from a vacuum chamber, then compressing it by tilting and infilling with mercury. The pressure in this smaller volume is then measured by a mercury manometer, and knowing the compression ratio (the ratio of the initial and final volumes), the pressure of the original vacuum can be ...