Temperature Correction for Mercury Barometers

The mercury in the barometer expands as the temperature increases. The barometer is calibrated for 0oC. For higher temperatures a correction must be applied to compensate for the expansion of the mercury. The following table shows the correction, in millimetres (mm), that should be subtracted from the reading of atmospheric pressure. For observed heights of the mercury column between the listed values, you may interpolate to determine the required correction.

Temperature (oC) Observed Height (mm)
740 750 760 770 780 790
17
18
19
20
21
22
23
24
25
2.05 2.08 2.10 2.13 2.16 2.19
2.17 2.20 2.23 2.26 2.29 2.32
2.29 2.32 2.35 2.38 2.41 2.44
2.41 2.44 2.47 2.51 2.54 2.57
2.53 2.56 2.60 2.63 2.67 2.70
2.65 2.69 2.72 2.76 2.79 2.83
2.77 2.81 2.84 2.88 2.92 2.96
2.89 2.93 2.97 3.01 3.05 3.08
3.01 3.05 3.09 3.13 3.17 3.21

The above text and table are by David M. Harrison of the Department of Physics at the University of Toronto.