Abstract
A method of estimating molal volume of organic liquids at any temperature by means of the addition of "contact volume" is suggested. Different from previous methods in which critical density and pressure data are indispensable basic information, the present method needs orthobaric melting point and critical temperature. Many organic liquids have been proved to have the same fixed values with respect to "contact volume", provided that the energy level parameter, θ, of the liquid defined by θ=(t-to)/(to-to) is the same. Where to=critical temperature, to=melting point, t=the temperature of the liquid.
"contact volume" is the local free volumes denoted by a2, ab, b2, be, ac, ... etc., where a, b, c, ... etc. represent the atomic groups CH3-, CH2=, -CH-, ... etc. Thus, the molal free volume of n-heptane, for instance, is shown to be
vf=Vt-Vo=ΣΔvf=(2a+5b)2=4a2+20ab+25b2
where Vt and Voare the molal volume at t and to respectively.
For some fifty organic liquids consisting of paraffins, aromatics and alcohols, vfin θ=0.05-0.60 have been analyzed.
The result shows good agreement with experimental data in the literature and endorses the new liquid corresponding state concept.
