Conductometric Titration for the Prediction of Conductivity in Solutions with Polymeric Membranes

The analytical technique of conductometric titration is used to characterize polymeric materials.This technique allows obtaining the polymer dry weight capacity(DWC) and the extent of reaction and establishing the optimal number of water molecules per sulfonic groups.In this particular case the polymer material under study was Nafion?117.Two different reactions were made: Neutralization and exchange.Both of them allow obtaining the same result.Conductometric titrations could be considered as a good method to study the neutralization and exchange reactions for polymeric materials used in fuel cells or electrolyzers.The implementation of this analytical technique allows reducing operation time of those types of materials.The waiting time between determinations permits to say that the amount of reactant consumed and products obtained were the same after each addition of titrant.

Conductometric Titration of Metformin Hydrochloride: Simulation and Experimentation

In order to teach students,the importance of conductometric titrations in this work,we present a laboratory experiment to quantify the amount of metformin hydrochloride in a tablet.The quantification was carried out through the evaluation of the chloride by silver nitrate.The titration and the end point were followed by conductometric titration,as well as by potentiometric and visually by the Volhard method.In addition,the theoretical conductivities of the metformin hydrochloride solution were calculated when known volumes of titrant are added,using the limit conductivity data for each of the ions present in the literature.To simulate the conductometric titration,the calculated conductivity values were plotted based on the volume of silver nitrate added.A comparison between techniques is made in order to determine the best monitoring method,being this one conductimetry to detect the equivalence point for metformin hydrochloride with 0.99±0.03,according to relative standard deviation(%RSD).Simulated titration curves adequately describe obtained results in an experimental way.The conductometric titration is the best method for quantification since it shows less dispersion between obtained results and has the highest concordance among results.Their application is shown through the analysis and conductometric titration simulations.

Syntheses and Properties of K_17[Ln(CuW_11O_39)_2]·xH_2O

Heteropoly-complexes K17[Ln(CuW11O39)2].xH2O(Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Dy) were prepared. The properties of the products were investigated by ion-exchange, conductometric titration, IR, UV and X-ray powder diffraction. The results show that the structure of the products is similar to that of U(a-Ge11O39)2 and consistent with the model proposed by Peacock.

Polar Gradient Latex Particles with Hydrophilic Core and Hydrophobic Shell Prepared via Multistep Emulsion Polymerization

Monodisperse polar gradient particles were synthesized via a three-step emulsion polymerization using poly（butyl acrylate-methyl metbacrylate-methacrylic acid-ethylene glycol dimethacrylate） （P（BA-MMA-MAA- EGDMA）） as core, poly（methyl methacrylate-methacrylic acid-styrene） （P（St-MMA-MAA）） as interlayer and polystyrene （PSt） as shell. The particle growth and encapsulation in each emulsion polymerization step were followed by transmission electron microscopy （TEM）, dynamic light scattering （DLS） and conductometric titration. Results indicated that the feeding mode and the interlayer were essential to prepare the polar gradient latex particles with hydrophilic core and hydrophobic shell. The morphologies of the two-layer core/interlayer and three-layer core/interlayer/shell particles were observed in TEM micrographs, and the sequential encapsulations of the carboxyl-containing core and the core/interlayer particles were confirmed by an increase in the particle size as well as an increase in the buried carboxyl percentage