This work is focused in studying the inclusion of chemical speciation in the characterization of mining tailings in Mexican regulation with a case study in Parral, Chihuahua, Mexico. In this site, high concentration of lead and arsenic in tailings located in the surroundings represent a high concern to the local population. The total concentration of Pb in the samples ranged from 78.03 ± 2.67 to 5748 ± 263.63 [mg kg^-1] and from 5.49 ± 0.43 to 509.84 ± 40.18 [mg kg^-1] for As. Chemical speciation was tested for samples that exceeded the limits of the Mexican Regulation using sequential extractions proposed by the Bureau Community of Reference (BCR) to obtain the distribution of lead and arsenic in four different fractions. The set of extractions consisted in the extractable/exchangeable fraction (F1), the reducible fraction (F2), the metals bound to organic matter and sulfides (F3) those under oxidizing conditions, and the residual fraction (RF). The results show that 70% of lead is found in F1 and F2 fractions while 20% is found in F3 fraction. In case of arsenic, 60% is found in residual fraction, 25% in fraction F3 and less than 15% in fractions F1 and F2.

A series of experiments based on problem-solving and collaborative-learning pedagogies are described that encourage students to interpret results and draw conclusions from data. Different approaches including parallel library synthesis, solvent variation, and leaving group variation are used to study a nucleophilic aromatic substitution of 1-halo-2,4-dinitrobenzene to obtain aryl-substituted 2,4-dinitrophenylamines. Determining the yield of each reaction in parallel synthesis allows students to make simple structure−reactivity relationships.

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In laboratory experiments it is common for students to acquire knowledge and develop the basic abilities needed to solve different types of problems related to synthesis and analysis. The students are so interested in this objective that they do not generally pay any attention to the wastes generated during their lab experiments. It is well known that experiments usually generate small quantities of a large variety of wastes. Nevertheless, the complexity of the wastes generated in the laboratories of educational institutions is large. Thus, detailed studies of their treatment should be undertaken. In North American and European universities the problem has been solved by sending these wastes to specialized companies that treat and dispose of them; however, in Mexico, such alternatives are not available owing to the high cost for waste disposal. Therefore, the Organic Chemistry Department of the Chemistry School at the National Autonomous University of Mexico has started a project concerned with the management and treatment of wastes generated during experimental lab sessions. In the United States and Europe, students do not generally treat their wastes. Therefore, it would be convenient to include this treatment as part of the educational aspects in organic experiments in all parts of the world to develop an environmentally conscience culture among them.

<p>En este trabajo es presenta una propuesta de protocolos experimentales en el contexto de la Química Forense como  proyectos para el desarrollo y validación de métodos analíticos, en los que se abordaron de forma adicional aspectos integradores de la carrera de química y de la aplicación de los mismos a situaciones plausibles en la realidad, para resaltar la importancia de la generación de resultados confiables que soporten la controversia jurídica. El proceso de enseñanza y aprendizaje se alcanza, ya que al final el estudiante es capaz de obtener los parámetros de validación para el tipo de pruebas cualitativas que se establecen en lo protocolos propuestos.</p>