Characterization of pH in liquid mixtures of methanol/H2O/CO2

The presence of H2O and CO2 in enhanced-fluidity liquids changes the pH in these mixtures due to the formation of carbonic acid. The acid-base equilib ria in enhanced-fluidity liquids will also be affected by the reduction in the dielectric constant with the addition of CO2. The pH of enhanced-fluidi ty liquid mixtures at room temperature was determined from the UV/visible a bsorption spectra of several pH indicators. pH values of methanol/H2O/CO2 m ixtures with CO2 proportions as high as 19.2 mol % are reported. The effect of adding buffer to methanol/H2O/CO2 mixtures on pH was also studied. It w as also shown that pressure variation did not significantly influence the p H of enhanced-fluidity liquids.