3.2 Benzene + hexane

In studies related to the thermodynamics of solutions, the experimental information generated by the binary benzene + hexane, for different properties, has been, and still is, used by researchers in that area as a reference of their investigations; therefore, the choice of this system is justified. Twenty-three useful VLE data series were found in the bibliography [26–42], 16 iso-p and 7 iso-T. Figure 3 shows important errors in some of the series [29, 31, 37] at 101 kPa, with data missing the trend observed in the other series. These are propagated to the T vs x,y representations (Figure 4(a)). The random error for these series is serious as evidenced in Figure 4(b).


### Table 1.

Values obtained in the application of the thermodynamic consistency-test to VLE data of acetone + ethanol at different conditions.

Figure 4 depicts the iso-p data set at pressures other than the atmospheric. Figure 5(b) indicates that three of the published series [28] (the ones that correspond to p = 610.8 kPa, 810.8 kPa, and 1013.5 kPa) show systematic errors, giving

Ref. [35] (+) Ref. [26] (◊) Ref. [37]; (�) Ref. [29]; (∇) Ref. [32]; (▷) Ref. [31]; (◁) Ref. [37].

Plot of iso-p VLE data of the binary benzene + hexane at 101 kPa. (a) T,x,y; (b) γ,x; g<sup>E</sup>

hE values for the binary acetone(1) + ethanol(2). (a) p = 101.32 kPa; (b) p = 400 kPa. (○) Ref. [20]; (�)

A Practical Fitting Method Involving a Trade-Off Decision in the Parametrization Procedure…

Ref. [21]; (□) Ref. [22]; (+) Ref. [23]; (△) Ref. [24]; (◊) Ref. [25].

DOI: http://dx.doi.org/10.5772/intechopen.85743

not reflect this anomalous behavior, so that probably they will be caused by a

the extreme points, at infinite dilution, which is a clear sign of inconsistency.

Available iso-T data series are represented in Figure 5. Data are found for the whole composition interval only at 333 and 345 K. Several series were measured at 333 K [40–42], allowing their comparison. From the representation of p,x,y (Figure 5(a)) and related mixing quantities (Figure 5(b)), an acceptable coincidence is observed. Two of the data sets (Ref. [41]) show negative values of g

Conclusions drawn from the visual inspection are confirmed by the consistency analysis presented in Table 2. Data series n° 11 is discarded since consistency cannot be evaluated due to the lack of data in the zone corresponding to x<sup>1</sup> > 0.2. All consistency tests, except the direct van Ness, did not accept the series measured at

systematic deficiency in the monitored temperature.

/RT < 0; thus γ<sup>i</sup> < 1 as x<sup>1</sup> ! 1. However, the representation of T vs x,y does

E /RT in

/RT,x. (○) Ref. [34]

rise to g E

53

Figure 3.

Figure 2.
