Question

Why don't${\mathbf{Cr}}^{\mathbf{3}\mathbf{+}}$and ${\mathbf{TiO}}^{\mathbf{2}\mathbf{+}}$interfere in the analysis of ${\mathbf{Fe}}^{\mathbf{3}\mathbf{+}}$when a Walden reductor, instead of a Jones reductor, is used for pre-reduction?

Short answer

Jones reductor is used, its potential is $-0.764\mathrm{V}\mathrm{so},{\mathrm{Cr}}^{3+}\mathrm{and}{\mathrm{TiO}}^{2+}$would get reduced. That’s way, they would interfere with the analysis of${\mathrm{Fe}}^{3+}$.

Step-by-step solution

Definition of Walden reductor.

• The Walden reductor is a reduction column filled with metallic silver that can be used to lower the oxidation state of a metal ion in aqueous solution.

• It can be used to convert ${\mathrm{UO}}_2^{2+}\mathrm{to}{\mathrm{U}}^{4+}$

Determine the Walden reductor used for pre-reduction.

• Walden reductor contains solid silver and $1\mathrm{MHCI}$and its reduction potential is $0.222\mathrm{V}$.

• The potential is high enough so ${\mathrm{Cr}}^{3+}\mathrm{and}{\mathrm{TiO}}^{2+}$ are not reduced and ${\mathrm{Fe}}^{3+}$can be reduced.

• On the other hand, when Jones reductor is used, its potential is $-0.764\mathrm{V}\mathrm{so}{\mathrm{Cr}}^{3‐}\mathrm{and}{\mathrm{TiO}}^{2\mathrm{\iota }}$would get reduced. That way, they would interfere with the analysis of ${\mathrm{Fe}}^{3\mathrm{\iota }}$.

• If required for chemical analyses, the Walden reductor can be employed to obtain chemical species in their low valence state, or to obtain small amounts of the compound in the suitable form.