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Nowadays microwave radiation is being researched to produce biodiesel from different raw materials due to the many advantages that this technology presents compared to traditional transesterification, such as shorter reaction times and less amount of heat energy to obtain biodiesel. The aim of this research was to explore the possibility of carrying out the microwave-assisted transesterification of macroalgae and compare the results with the traditional transesterification. For that reason, some experiences were conducted using sunflower oil and macroalgae as raw material. Based on the obtained results, the best conditions for microwave-assisted transesterification reaction were macroalgae to methanol ratio of 1:15 (wt/vol), sodium hydroxide concentration of 2 wt % and reaction time of 3 min.

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The refractive indices of lithium, magnesium, and copper sulfate in ethanol + water solutions were measured over the temperature range (288.15 to 318.15) K and at atmospheric pressure. Also, ethanol + water and single salt + water binary systems were measured. Binary and ternary systems were correlated using polynomial expressions, and the parameters depend on the composition of the mixtures. Data fitting shows good agreement with experimental values.

The objective of this work is to share the authors' experience towards a different mode of teaching/learning method. Cooperative learning (Jigsaw) was employed on the University of Vigo's fourth-year engineering students. The results of the experience show that cooperative learning is quite a viable alternative to the classical way of lecturing at the university when the number of students is not too high. The authors' observation indicates that students did not show a lot of interest towards the new learning style but their resistance changed once they began the activity. The Jigsaw method has proved to be a useful tool for improving the learning process so that students have the opportunity to participate actively in the learning activities.

The solubilities of (sodium and copper(II)) sulfate þ ethanol þ water mixtures have been determined at (278.15, 288.15, and 298.15) K and for the potassium sulfate þ ethanol þ water system at the same temperatures and also at (308.15 and 318.15) K. The equilibrium composition for different points has been calculated by means of refraction index and density measurements. An empirical correlation for the solubilities of the ternary mixtures has been used to correlate experimental values as a function of the solvent composition. Data fitting shows a good agreement with experimental values.

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