## 3 Results and Discussion
### The Influence of n-Hexane and Ethanol on the Viscosity, Density and Surface Tension of Canola Oil  
Canola oil cannot be directly applied for diesel engines that are adapted to diesel fuel. In order to use it as a possible fuel for diesel engines, its physicochemical properties must be changed, especially the viscosity of the oil should be significantly reduced. The viscosity of studied canola oil is equal to 70.45 mPa-s, but it should be noted that it is smaller than for example the viscosity of olive and peanut oil, but greater than those of corn and soybean oils [37; 38; 39; 40; 41; 42]. This is made possible by the addition to the canola oil substances whose properties such as viscosity, density and surface tension are much smaller than those of the oil. It proved that the addition of n-hexane to canola oil decreases its viscosity, surface tension and density without significant changes of capacity heat [15]. However, despite a significant reduction affected by n-hexane the viscosity of canola oil was significantly larger than that of diesel fuel. From this point of view, for greater improvement of the canola oil viscosity, not only n-hexane, but also ethanol was added. Ethanol was introduced to the mixture of canola oil and n-hexane by contact with the mixture. It proved that the viscosity of canola oil after the contact with ethanol is significantly reduced from 70.45 to 36.61 mPa-s (Figure 3). After the contact of ethanol with the canola oil and n-hexane mixture the dynamic viscosity of the mixture decreases with the n-hexane concentration increase. This decrease is larger than that of the canola oil and n-hexane mixture without the alcohol contact with this mixture. At the concentration of n-hexane equal to 20% the viscosity of the mixture being in contact with ethanol is practically close to that of the canola oil + n-hexane (20%) mixture (Figure 3). As mentioned above the viscosity of the liquids at a given temperature depends on the interactions between the liquid molecules and the distance between them. The magnitude of these interactions depends on the type of the liquids. In the case of the liquids such as fatty acids whose molecules can be divided into two parts--hydrophobic and hydrophilic--the main contribution to the intermolecular interactions comes from the dispersion and acid-base forces. As the surface tension of n-hexane results only from the dispersion force [26; 27] and is considerably smaller than that of fatty acids (Table 1) [43], the presence of n-hexane in canola oil is expected to cause the decrease in the dispersion interactions between the molecules of canola oil components and to increase the distance between these molecules. On the other hand, the contact of ethanol with canola oil causes the decrease in the viscosity from 70.45 to 36.61 mPa-s (Figure 3), as was mentioned above. Figure 3: The plot of the viscosity (\(\eta\)) of the canola oil + n-hexane + ethanol mixture (curve 1) and canola oil + n-hexane mixture (curve 2) vs. the n-hexane concentration (\(C_{p}\)). (The first point corresponding to the 0% n-hexane concentration on curve 1 this is the viscosity of canola oil + ethanol mixture; the first point corresponding to 0% n-hexane concentration on curve 2 this is the viscosity of canola oil). It seems that during the contact of ethanol with canola oil some substances are extracted to the ethanol phase and the structure of canola oil is changed. Probably the distance between the fatty acid molecules increases slightly. For this reason, the dispersion forces decreases significantly. On the other hand, ethanol penetrates into the oil phase and can influence also on the acid-base intermolecular interactions between the fatty acids. Considering the changes of the canola oil viscosity it should be remembered that the viscosity of n-hexane (0.3102 mPa\(\cdot\)s) and ethanol (1.22 mPa\(\cdot\)s) (Table 1) is considerably smaller than that for canola oil (70.45 mPa\(\cdot\)s) (Table 1) [15; 43; 44].