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Inch of mercury (inHg and ″Hg) is a non-SI unit of measurement for pressure. It is used for barometric pressure in weather reports , refrigeration and aviation in the United States . It is the pressure exerted by a column of mercury 1 inch (25.4 mm) in height at the standard acceleration of gravity .
A glass McLeod gauge, drained of mercury. A McLeod gauge is a scientific instrument used to measure very low pressures, down to 10 −6 Torr (0.133 mPa). It was invented in 1874 by Herbert McLeod (1841–1923). [1] McLeod gauges were once commonly found attached to equipment that operates under vacuum, such as a lyophilizer. Today, however ...
After filling, the gauge is then cut away again. Further, the vacuum in the gauge eventually deteriorates due to slow diffusion of gases through the mercury, making the device inaccurate. [8] In 1938, Adolph Zimmerli (1886–1967) [9] invented a gauge that overcame the filling problems, at least for pressures below ambient pressure. [10]
Thereafter, research into the partial vacuum lapsed until 1850 when August Toepler invented the Toepler pump and in 1855 when Heinrich Geissler invented the mercury displacement pump, achieving a partial vacuum of about 10 Pa (0.1 Torr). A number of electrical properties become observable at this vacuum level, which renewed interest in further ...
Single-stage vacuum pumps typically produce vacuum to 35 torr (mm Hg) or 47 millibars (4.7 kPa), and two-stage pumps can produce vacuum to 25 torr, assuming air is being pumped and the ring-liquid is water at 15 °C (59 °F) or less. Dry air and 15 °C sealant-water temperature is the standard performance basis, which most manufacturers use for ...
From October 2008 to December 2012, if you bought shares in companies when Robert J. Alpern joined the board, and sold them when she left, you would have a 32.5 percent return on your investment, compared to a 58.6 percent return from the S&P 500.
The absolute pressure of 10 to 40 mmHg in the vacuum column is most often achieved by using multiple stages of steam jet ejectors. [16] Many industries, other than the petroleum refining industry, use vacuum distillation on a much smaller scale.
Amid the ongoing McDonald's E. coli investigation, Fox News Digital spoke with several food safety experts about the most prevalent foodborne illnesses and how to prevent them.