Curvature of the vapour pressure curve

This paper brings out the existence of the maximum in the curvature of the vapour pressure curve. It occurs in the reduced temperature range of 0.6-0. 7 for all liquids and has a value of 3.8-4.8. A set of 17 working fluids co nsisting of several refrigerants, carbon dioxide, cryogenic liquids and wat er are taken as test fluids. There exists also a minimum dose to the critic al point which can be observed only when a thermodynamically consistent fun ctional form of the vapour pressure equation is chosen. This feature, in ad dition to throwing some light on the behaviour of the vapour pressure curve , could provide some useful inputs to the choice of working fluids for vapo ur pressure thermometers and thermostatic expansion valves, (C) 2001 Elsevi er Science B.V. All rights reserved.