3.4: LeBas molar volume

Table 3.6 Additive volume increments for calculating LeBas molar volume, (Cussler,...

Calculate the LeBas molar volume for toluene (methyl benzene). 

Figure 3.4 Activation energies of contaminant sampling by SPMDs as a function of molar volume (LeBas method). PAHs—filled circles Huckins et al. (1999) filled squares Booij et al. (2003a) pesticides—open circles Huckins et al. (2002b) chlorobenzenes and PCBs—open squares Booij et al. (2003b) planar PCBs— triangles Rantalainen et al. (2000) and PCDD/Fs—asterisks Rantalainen et al. (2000).

Molar volume can also be calculated by additive fragment methods [Elbro et al, 1991 Schotte, 1992] such as the fragment method of LeBas [Reid et al, 1988]. Moreover, it is frequently used as a measure of the - cavity term in - linear solvation energy relationships. 

Values of Dm for the hydrophilic solutes in p-HEMA and p-HEMA crosslinked with 1 mole % EGDMA are shown in Tables I and II. It is evident that the Dm values in the crosslinked membrane are smaller than in p-HEMA. Plots of these values according to Eq. 3 are shown in Fig. 1. A semiemperical equation developed by Wilke and Chang (13) was utilized to calculate Dq. The molar volume of the solute was estimated from atomic contributions according to LeBas (14). The molecular radii, tq, given in Table I were calculated assuming that the solutes were spherical (15). 

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