CONCENTRATED HYDROCHLORIC-ACID MEDIA - ACID-BASE, OXIDATION REDUCTION, AND SOLVATION PROPERTIES

The acidity level and the chloride anion activity are evaluated In H2O-HCI mixtures (1.0 < |HCI| < 12.0 M) by means of Ro(H) and Ro(CI-) functions. For both functions, the potentials of the ferrocenlum/ferrocene system (Fc+/Fc) are used as reference potentials. Hydrogen and calomel electrodes are respectively employed for acidity level and chloride anion activity evaluations. It is shown that Ro(H) decreases from 0 to -6.2 and Ro(CI-) from 0 to -4.8 when HCI concentration Increases from 1.0 to 12.0 M. Redox properties of some Mn++/M(Hg) couples (Mn+= Ag+, Pb2+, Cu+, Sn2+, Cd2+) are examined. The solvation transfer activity coefficient (f) of ions Mn+are calculated with use of the standard potential values of the corresponding redox systems. Mn+ions, considerably solvated in H2O-HCI mixtures (specific Interactions with Cl-) have a reactivity that varies very little with increasing HCI concentration. The f values for Nl22+and Fe3+determined from constants of liquid-liquid extraction show a desolvation of these Ions with Increasing HCI concentration. © 1990, American Chemical Society. All rights reserved.