Correlations between normal boiling points and critical parameters (critical temperatures and critical pressures) and between normal boiling points and acentric factors of normal and branched paraffins in the range from C-7 to C-100 have been developed. These correlations can be used to quickly and easily compute critical properties that allow to reproduce closely, by means of the Soave-Redlich-Kwong (SRK) equation of state (EoS), the vapour pressure of pure compounds. In the range of 0.5-5 mmHg the values of vapour pressure calculated by means of the SRK EoS become less accurate and they can be improved using a different equation for the temperature-depending attractive parameter (i.e., the Mathias-Copeman alpha function) instead of the classical Soave function. (C) 2008 Elsevier B.V. All rights reserved.