Jelly Potentiometry, Do It Yourself

Understanding potentiometry is a difficult task when students in initial courses of Analytical Chemistry are first introduced to instrumental techniques. The closest instrument to them is a pH meter, which is frequently used as a “black box”, without a real understanding of how it works. Here we present the assembly of jelly modules that the students can combine in different ways with the purpose of visualizing what reference and indicator electrodes are and their function when they are used in potentiometric measurements with quantitative purposes. This didactic sequence was used during six semesters in a first course of Analytical Chemistry dictated for students becoming laboratory technicians in Chemistry and Chemical Engineering. It is a hands-on experiment to exemplify both a direct potentiometric analysis and a potentiometric titration (indirect analysis). It is simple, low-cost, and easy to apply. It only requires gelatin, salts, pieces of metal, and a multimeter. The students showed interest in its execution, and they were able to identify the functions of the electrodes, discuss the different analytical implications of potentiometric techniques among themselves, and make the requested graphics with very good results.Fil: Sosa, Griselda Leonor. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Deluchi, Guido Enrico. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Ramírez, Silvana A.. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Hamer, Mariana. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Characterization of diatomaceous earth modified by organic ligands for enhanced zinc adsorption

In order to enhance zinc adsorption, natural diatomaceous earth was modified by a simple batch procedure incorporating ligands with carboxylic and amine functional groups: ethylenediaminetetraacetic acid and 2-N(hydroxyethyl) iminodiacetic acid were used. The supernatants were analysed by square wave anodic stripping voltammetry monitored titrations to quantify ligand incorporation to the diatomaceous earth. The solids were characterized by energy-dispersive X-ray spectroscopy, scanning electron microscopy, X-ray diffraction, electrophoretic mobility, Fourier transform infrared spectroscopy and thermogravimetric analyses. Ligands modified the surface of the natural solid and were unable to enter the interlayer space of the smectite, main component of diatomaceous earth. Langmuir model was the most suitable to describe Zn(II) adsorption on diatomaceous earth whereas Freundlich showed better fit to data of the modified solids. The incorporation of organic ligands increased zinc retention by ca. 50%.Fil: Sosa, Griselda Leonor. Universidad Nacional de General Sarmiento. Instituto de Ciencias. Área de Biología y Bioinformática; ArgentinaFil: Fernández Morantes, César. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; ArgentinaFil: Flores, Federico Manuel. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; ArgentinaFil: Torres Sanchez, Rosa Maria. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; ArgentinaFil: Zalts, Anita. Universidad Nacional de General Sarmiento. Instituto de Ciencias. Área de Biología y Bioinformática; ArgentinaFil: Ramírez, Silvana Andrea María. Universidad Nacional de General Sarmiento. Instituto de Ciencias. Área de Biología y Bioinformática; Argentin