**Figure 10.**

*Color variation of solutions of t-Bu5RB and pure diesel and ethanol and in solutions of ethanol (%v/v) in diesel. Adapted from El Seoud et al. [42].*

Galgano et al. have also used the solvatochromic dye 2,6-bis[4-(tert-butyl) phenyl]-4-{2,4,6-tris[4-(tert-butyl)phenyl]-pyridinium-1-yl}phenolate (t-Bu)5RB) to make quantitative analyses of bioethanol and mixtures of bioethanol with gasoline and water in an experiment based on a constructivist approach for undergraduates in a chemistry class [43].

Solutions of the dye in ethanol-water and anhydrous ethanol-gasoline mixtures evidenced solvatochromic effects, with the color changing according to the composition of the mixture, as shown in **Figure 11.**

The results of using solvatochromic effects of different dyes in mixtures, especially involving additized or altered fuels, seem extremely promising for the development of alternative colorimetric methods with field applications.
