Protonic acidity scales in the system n-butyl alcohol — water

Abstract

The scales of acidity are developed by providing a set of standard buffer solutions in different mixtures of normal butyl alcohol with water outside the region of stratification. The acidity values are estimated by the US NBS method in cells without liquid junction. The glass electrode is used as an indicator electrode within a wide range of pH. The method allows the acquisition of the values brought closest to a theoretical measure of acidity: p a H + ∗ = − log a H + ∗ (where a H + ∗ is the proton activity standardized to infinite dilution in the corresponding solvent). In 100% butanol the method is modified by taking into account the electrolyte's incomplete dissociation as well as by using equilibrium constants of processes occurring in complex buffer systems. Protolytic equilibria of a series of indicators (sulfonphthalein and xanthene dyes) are investigated spectrophotometrically in butanol within a wide acidity range.