Correction of Barometer Readings

Steroid Hormones and Other Steroidal Synthetics Sublimation Pressure for Organic Compounds Surface Tension of Liquid Elements Temperature Correction for Barometer Readings Temperature Correction for Glass Volumetric Apparatus Temperature Correction for Volumetric Solutions Temperature Correction, Glass Scale... 

For records on weather maps, meteoroiogists customariiy correct barometer readings to sea ievei, and some barometers may be caiibrated accordingiy. Such instruments are not suitabie for iaboratory use where true pressure under standard conditions is required. Scaie corrections shouid be specified in the maker s instructions with the instrument, and are aiso indicated by the iack of correspondence between a gauge mark usuaiiy piaced exactiy 76.2 cm from the zero point and the 76.2-cm scaie graduation. 

The mercury barometer (Fig. 10-11) indicates directly the absolute pressure of the atmosphere in terms of height of the mercuiy column. Normal (standard) barometric pressure is 101.325 kPa by definition. Equivalents of this pressure in other units are 760 mm mercury (at 0°C), 29.921 iuHg (at 0°C), 14.696 IbFin, and 1 atm. For cases in which barometer readings, when expressed by the height of a mercuiy column, must be corrected to standard temperature (usually 0°C), appropriate temperature correction factors are given in ASME PTC, op. cit., pp. 23-26 and Weast, Handbook of Chemistty and Physics, 59th ed., Chemical Rubber, Cleveland, 1978-1979, pp. E39-E41. 

A mercury barometer reading of 728.3 mm is obtained at 23°C with a brass scale. What is the barometer reading "corrected to 0°C"—that is, in torr ... 

The entries A in the table below are calculated from Eq. (XVlll-1) on the assumption that the barometer has a brass scale graduated to be accurate at 0°C. See Chapter XIX for a description of the recommended procedure for reading a barometer. These corrections should be subtracted from the observed barometer readings i.e., p(Torr) = PobsCnun, 7) — A. (If the brass scale is accurate at 20°C, the appropriate corrections are approximately 0.3 mm greater than those given.) Once the barometer reading has been corrected to 0°C, the pressure is referred to as Torr rather than mm Hg. 

Total Suction Head This is the reading h, of a gauge at the suction flange of a pump (corrected to the pump centerline°), plus the barometer reading and the velocity head h at the point of gauge attachment ... 

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