what the f does millimeters of mercury mean?

Question

i know its a measurement of pressure, but it makes no sense on the surface, unlike something staightforward like pounds per square inch.

Answer 1

You know how when you suck on a straw you get your drink to move up through the straw? This happens because by sucking, you are creating a partial vacuum on one side of the straw, and the atmospheric pressure on the liquid on the other side, now having nothing to counter it, pushes the liquid up through the straw. But no matter how much you suck, you cannot reduce the pressure on your side of the straw to less than zero (i.e. a complete vacuum), and as such there is a maximum height to which you can raise a column of water - that height depends solely on the atmospheric pressure on the other side of the straw. This means that you can construct a barometer simply by having a glass tube immersed vertically in some liquid, and pumping out all the air on one side of the tube, and then sealing the tube - the height of the liquid then gives you the ambient air pressure. Water, however, is not very dense, and so your barometer would have to be very large if it used water. To get around this problem, scientists use Mercury, which is a much denser liquid, to measure the pressure. A pressure of 1 mm Hg is simply a pressure that can support a column of Mercury 1 mm high under this arrangement.

Answer 2

Actually, mm of Hg are millimeters of liquid mercury that goes up a small pipe to measure pressure.

One way to define pressure is in terms of the height of a column of fluid that may be supported by that pressure; or the height of a column of fluid that exerts that pressure at its base. Although a manometer may use any fluid in principle, common fluids like water give heights that cannot be contained in a normal room. A water column needs to be of the order of 10 metres high to exert 1 atmosphere of pressure. Therefore a very dense fluid is required—mercury. Normal atmospheric pressure can support around 760 mm (29.92 in) of mercury; hence 1/760 of an atmosphere, or 1 mm of mercury (mmHg), has been a convenient measure of pressure for a long time, and is sometimes also called a torr.

Answer 3

you would prefer the old version "inches of mercury"?
it makes the same amount of sense.

Just depends on how you think about it

Answer 4

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