ABSTRACT
We have seen already that the Kelvin absolute temperature was defined to be identical with the ideal gas scale and so, as long as we have real gases whose equation of state can be accurately measured at very low pressures, we have a practical way of realising the absolute scale of temperature. The practicality of this, however, disappears at both low and high temperatures: at high temperatures because it becomes impossible to contain the gas (the containers soften or melt); at low temperatures because gases effectively cease to exist.
