1. AnalysisTo analyze correctly the data given, as it was explained before, test T of Student was used which requires ofsome entrances; initially, it was calculated tcal as follows:Using this equation, it was proceeded with the verification of tabulated number in the distribution t ofStudent, resulting 2.015. In which case, if t cal > t tabulated, the data must be discarded, in case it is not so, thisdata must not to be discarded. Then, when it is known that none of the data was discarded, an average with thatinformation was calculated for each output (TOP and BOTTOM), by the lineal equation of refractive index vscomposition it was calculated from each part the compositions resulting in:Table 1. Experimental composition and refractive index.Furthermore, with the data from column, it is known that for begin the procedure it is necessary to have theY-X diagram for the more volatile compound, in this case, ethanol diagram must be done as it shows: Figure 7. Y-X Diagram for Ethanol-Water at a P=1atm.