Water activity in acid solutions using the ferrocene redox system
Résumé
The Eo potential of ferricinium/ferrocene system (Fc+/Fc), detd. by differential pulse polarog. and referred to the KCl satd. calomel electrode (SCE) placed in a sep. compartment contg. 0.1 M phosphoric acid, has a const. value in concd. acid solns. with an equal water activity. Phosphoric, hydrochloric, perchloric, sulfuric, hexafluorosilicic acids and their binary and ternary mixts. were considered. This result may be used in some cases to evaluate water activity and acidity level without pH indicating systems being required.