Division 1.3 PRINCIPLE OF THE TEST

In general, the vapour pressure is determined at various temperatures. In a limited temperature range, the logarithm of the vapour pressure of a pure substance is a linear function of the inverse of the thermodynamic temperature according to the simplified Clapeyron-Clausius equation:

$$\log p=\Delta \frac{\mathrm{Hv}}{\mathrm{2,3}}\mathrm{RT}+\mathrm{constant}$$

where:

p

the vapour pressure in pascals

ΔHv

the heat of vaporisation in J mol^–1

R

the universal gas constant, 8,314 J mol^–1 K^–1

T

the temperature in K