2.7 Low and High Temperature Thermometry
The low temperature range is bounded by a limit 0°C, that is, 273 K and approach towards the limit of low temperature (see Fig. 2.6).
Fig. 2.6 Sketch showing low temperature measurement
First, we take the case of mercury thermometers. The lower range of a mercury thermometer is limited by the fact that it freezes at −38.87°C. So, temperature below −39°C cannot be measured by mercury thermometer. With alcohol thermometers which freeze at −111.8°C, temperature below the freezing point cannot be measured. But difficulty arises in the fact that the contractions of mercury and alcohol are not uniform ...