Criteria for Standardization of pH Measurements in Organic Solvents and Water + Organic Solvent Mixtures of Moderate to High Permittivities

pH standardization in aqueous solutions may now be considered as substantially achieved. The experimental work done so far in pioneering pH standardization in nonaqueous and mixed solvents, an extension which is very important for chemistry and chemical engineering, though based on sound physicochemical principles is regrettably fragmentary and scarce. Systematic acquisition of data is urgently needed for many important media, although the field is apparently almost unlimited. Doing this without valid and recognized objectives might clearly result in a disorienting and chaotic situation. This paper defines as many pH standards, pH//S, as necessary to cover the normal scale length of pH in each solvent, within the usual range of temperatures. This requires the appropriate experimental work and an extra-thermodynamic procedure, which is a logical extension of what is now endorsed, and currently applied, in the case of aqueous solutions.