## 3 Results and Discussion
### The Influence of n-Hexane and Ethanol on the Viscosity, Density and Surface Tension of Canola Oil
The mutual dissolution of n-hexane and ethanol affects the interface tension of canola oil-n-hexane and canola oil-ethanol as well as n-hexane-ethanol. The interface tension of canola oil with n-hexane-ethanol decreases with the increasing concentration of n-hexane in canola oil (Figure 9). This tension at the n-hexane concentration equal to 20% (1.6 mN/m) is close to that of the ethanol-n-hexane interface tension (1.42 mN/m). The interface tension is connected with the surface tension of the two phases being in the contact. In the literature there are many approaches to express the liquid-liquid and/or solid-liquid interface tension as a function of the surface one. Among them, these of [PERSON] et al. [27,48] and [PERSON] and [PERSON] [49] are the most often applied in practice. According to [PERSON] et al. [27,28] one can write the following:  
\[\gamma_{ij}=\gamma_{i}+\gamma_{j}-2\sqrt{\gamma_{i}^{LW}\gamma_{j}^{LW}}-2 \sqrt{\gamma_{i}^{+}\gamma_{j}^{-}}-2\sqrt{\gamma_{i}^{-}\gamma_{j}^{+}} \tag{4}\]  
where \(\gamma\) is the surface tension of the liquid or the solid and \(\gamma^{LW}\) is the Lifshitz-van der Waals component of \(\gamma\), \(\gamma^{+}\) and \(\gamma^{-}\) are the electron-acceptor and the electron-donor parameters of the acid-base component (\(\gamma^{AB}\)) of the surface tension, respectively. The subscripts \(i\) and \(j\) refer to phases \(i\) and \(j\). [PERSON] and [PERSON] proposed the following equation [49]:  
\[\gamma_{ij}=\gamma_{i}+\gamma_{j}-2\sqrt{\gamma_{i}^{a}\gamma_{j}^{a}}-2\sqrt {\gamma_{i}^{p}\gamma_{j}^{p}} \tag{5}\]  
where \(a\) and \(p\) refer to the dispersion (apolar) and polar components of the surface tension of a given phase. In the case when the surface tension of at least one phase results only from the Lifshitz-van der Waals or dispersion intermolecular interactions Equations (2) and (5) assumed the simpler forms [26,27]:  
\[\gamma_{ij}=\gamma_{i}+\gamma_{j}-2\sqrt{\gamma_{i}^{LW}\gamma_{j}^{LW}} \tag{6}\]  
and  
\[\gamma_{ij}=\gamma_{i}+\gamma_{j}-2\sqrt{\gamma_{i}^{a}\gamma_{j}^{a}} \tag{7}\]  
Assuming that there is not mutual dissolution of the n-hexane and alcohol and knowing that the surface tension of n-hexane results only from the Lifshitz-van der Waals intermolecular interactions the n-hexane-ethanol interface tension was calculated from Equation (6) and is equal to 1.91 mN/m. As for n-hexane and ethanol, the Lifshitz-van der Waals and dispersion component has the same value, and the n-hexane-ethanol interface tension calculated from Equation (7) has the same value as that calculated from Equation (6). The measured value of n-hexane-ethanol interface tension is equal to 1.42 mN/m. This indicates that the mutual n-hexane and ethanol dissolution changes the interface tension value. In turn, let us assume that the solution of n-hexane in the ethanol is ideal. In such a case the composition of the solution can be determined based on the surface tension. As  
Figure 9: The plot of the measured interface tension (\(\gamma_{LL}\)) between canola oil + n-hexane and ethanol phases (curve 1) as well as determined from Equation (5) (curve 2) and Equation (4) (curve 3) vs. the n-hexane concentration (\(C_{p}\)). mentioned above the surface tension of the ethanol saturated by n-hexane was equal to 20.4 mN/m. Thus, for the ideal n-hexane solution in ethanol the mole fraction of n-hexane is equal to 0.59. In such case Equations (6) and (7) are not fulfilled.