Several literature relations proposed by Vetere are re-examined to simplify their analytical form and to improve their performances. Their results are compared with those of three old literature equations, namely the equations by Riedel, Chen and Liu. On the whole, four of them embody universal parameters, which can be used for any type of compounds and require Tb and the critical constants Tc and Pc in order to be applied. Regarding the other ones, three are function of Tb and molecular weight M, and the last three need as input parameters M and the polar parameter Wp .The parameters of the equation which disregard the use of the critical constants must be optimised separately for three classes of compounds, namely hydrocarbons, polar compounds and alcohols. Further, to have a severe test, nearly 290 experimental data of ΔHvb were processed, chosen from the most reliable reported in the fifth edition of The Properties of Gases and Liquids.
