The Inverted Philosopher’s Stone: how to turn silver to a base metal

Abstract

Metals often are classified as “noble” or “base”—characterizing their reduction potential as one of the most important chemical properties. We show that metals are only as noble as allowed by their environment, i.e. this is a relative term, and the “frame of reference” simply is the solvent in which the redox system is present. We prove that silver is a prime example for a noble metal that forfeits its noble character in the simple ionic liquid HMIM Br (1-hexyl-3-methylimidazolium bromide) as an example for such a solvent.

Bichloride-based ionic liquids for the merged storage, processing, and electrolysis of hydrogen chloride

“…S5 and table S2). As the applicability of reference systems in ionic liquids is still under investigation, an exact determination of the absolute potentials is only possible to a limited extent ( 41 ). However, it still allows determining the decomposition voltage which can be obtained from the difference between oxidation and reduction potential.…”

The Unified Redox Scale for All Solvents: Consistency and Gibbs Transfer Energies of Electrolytes from their Constituent Single Ions

“…In AN, the redox potentials of the Ag + /Ag system and of the H + /H 2 system are exceptionally close together, thus indicating a similar solvation of Ag + ions and H + ions by AN. It was shown that the relationship between H + and Ag + solvation can be reversed: Ag + is more strongly solvated than H + in the ionic liquid 1‐hexyl‐3‐methylimidazolium bromide, i. e., silver is a “non‐precious” metal in this medium [53] . Concerning the Cl − ion, a comparatively weak solvation is observed in aprotic solvents: to force Cl − (by electronation of Cl 2 ) into solution, a comparatively low redox potential is already sufficient.…”

“…It was shown that the relationship between H + and Ag + solvation can be reversed: Ag + is more strongly solvated than H + in the ionic liquid 1-hexyl-3-methylimidazolium bromide, i. e., silver is a "non-precious" metal in this medium. [53] Concerning the Cl À ion, a comparatively weak solvation is observed in aprotic solvents: to force Cl À (by electronation of Cl 2 ) into solution, a comparatively low redox potential is already sufficient. Thus, chlorine is a much weaker oxidant in aprotic solvents than in protic solvents, and in PC it is even a weaker oxidant than the Ag + ion.…”