Alfredo Gómez

Thermodynamic Study of the Solubility of Some Sulfonamides in Octanol, Water, and the Mutually Saturated Solvents

The free energy, enthalpy and entropy of solution, were evaluated from solubility data for a group of sulfonamides from 25 to 40°C in octanol, water, and the mutually saturated solvents. In aqueous media, the solubility was determined at the isoelectric point and ionic strength 0.15 mol-L−1. The excess free energy and the activity coefficients of the solutes also were determined. The results are discussed in terms of solute–solvent interactions.

Thermodynamic study of the solubility of some sulfonamides in cyclohexane

The thermodynamic functions Gibbs energy, enthalpy and entropy of solution in cyclohexane, were evaluated from solubility data for a group of sulfonamides over the temperature range from 20.0 to 40.0 °C. The excess Gibbs energy and the activity coefficients of the solutes were also determined. The results are discussed in terms of solute-solvent interactions.

Estimation of the solubility of sulfonamides in aqueous media from partition coefficients and entropies of fusion

Semi empirical equation developed by Yalkowsky and Valvani, and another equation extended by Jain and Yalkowsky were used to estimate the aqueous solubility S w , of some sulfonamides using experimental octanol-water partition coefficients P , entropies of fusion j S f , and melting points t m , determined by DSC measurements. The calculated solubilities were compared with those experimentally determined. When experimental j S f and t m were used, the S w calculated values were in good agreement in most cases.

A Heat-Conduction Flow Microcalorimeter for Solute Transfer Enthalpy Determinations. Design And Calibration

Abstract The construction of a heat-conduction flow microcalorimeter of the twin type, that uses thermopiles to detect thermal changes in the reference and reaction cells, is described. For comparative purposes, gold and silver cells, with different geometric shapes, are used. The calorimetric set is immersed in a water thermostat at a temperature of 25.000 ± 0.005°C. The thermostat is placed in a room whose temperature is controlled to 25.0 ± 0.2°C by an air thermostat. The calibration constant of the apparatus is determined for several values of electric work and power. Values of 22 WV1 and 14 WV1 are obtained for the gold and silver cells, respectively. The influence of the flow rate on the potential signal is studied. Chemical calibrations are performed with HCl-NaOH, THAM-HCl (trihidroxymethylaminomethane), and urea-water systems at different flow rates. The results are in good agreement with those reported in the literature.

Applicability of the Stoeckli-Bansal-Donnet Equation for the Determination of Total Area of Active Carbons by Microcalorimetry of Immersion

Abstract Total and external surface area for different samples of active carbons are determined by immersion microcalorimetry at 25,00 ± 0,01°C utilizing CCl4, as solvent; the data obtained shows the applicability of the Stoeckli-Kraehenbuehl equation for highly microporous carbons, and also it shows the functionability of the Stoeckli-Bansal-Donnet equation for active carbons without implying that they are essentially microporous.