Equations are provided for the estimation of critical constants, freezing point, boiling point, accentric factor, density, refractive index, and surface tension of n-alkanes, n-alkylcyclopentanes, n-alkylcyclohexanes, and n-alkylbenzenes in terms of molecular weight. The equations show internal consistency among various properties for high molecular weight compounds. The properties of petroleum mixtures have been estimated through proposed equations, and it is shown that the equations can be used to estimate properties of heavy petroleum mixtures.