The Elements of Qualitative Chemical Analysis, vol. 1, parts 1 and 2. / With Special Consideration of the Application of the Laws of Equilibrium and of the Modern Theories of Solution.

by Julius Stieglitz

[U⁶⁺] = [UO₂²⁺] × [H⁺]⁴ × k_base / (K_HOH)⁴.

(5)

[p287]

In other words, we may substitute [U⁶⁺] and a constant factor K_HOH⁴ / k_base for [UO₂²⁺] × [H⁺]⁴ in the first term (numerator) of the oxidation-reduction equation (3), derived from Luther's quantitative work. We thus obtain:

[U⁶⁺] / [U⁴⁺] = K_equil. × k_base / K_HOH⁴ = K,

(6)

which must agree just as well with the quantitative data,[575] as does the original equilibrium equation (3). It follows, that we may write the chemical equation, for the action in acid solutions, simply U⁶⁺ ⇄ U⁴⁺, exactly as we have Fe³⁺ ⇄ Fe²⁺ (p. [269]). [U⁶⁺] cannot be measured, as yet, but in the analogous case of Fe³⁺ ⇄ Fe²⁺, where both terms of the equilibrium equation are accessible to direct measurement, the experimental evidence distinctly favors[576] the views expressed.[577]

Permanganic Acid, Chromic Acids, etc., as Oxidizing Agents.

If we bring permanganate, against potassium iodide, into the beakers of the chemometer (p. [253]), we find that it is a much more vigorous oxidizing agent than is arsenic acid, and again we find that the addition of acid (sulphuric) to the permanganate solution enormously increases the potential (exp.) and therefore its oxidizing power. The addition of an acid would, obviously, enormously increase the concentration of a positive septavalent ion, if permanganic acid is assumed to be, to a slight extent, base forming and therefore amphoteric:

H⁺ + MnO₄⁻ ⇄ (HO)MnO₃
(HO)MnO₃ + 3 HOH ⇄ Mn(OH)₇ ⥃ Mn⁷⁺ + 7 OH⁻.