The remarkable property of gases that makes them so valuable in thermometry is displayed
in Fig. 6.2 [reproduced here as Fig. 1.2] where the product of pv is plotted against p for
four different gases, all at the temperature of boiling sulfur in the top graph, all at the
temperature of boiling water in the one beneath, all at the triple point of water in the next
lower graph, and all at the temperature of solid CO 2 in the lowest. In each case it is seen
that, as the pressure approaches zero, the product of pv approaches the same value for all
[four] gases at the same temperature.
Fig. 1.2 The fundamental property of gases is that the product of pv in the limit of p approaching
zero is independent of the nature of the gas and depends only on temperature
12
1 Introduction: Temperature and Some Comment on Work