The Walden reductor is a reduction column filled with metallic

silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...

which can be used to reduce a metal ion in aqueous solution to a lower

oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...

. It can be used ''e.g.'' to reduce UO₂²⁺ to U⁴⁺. The method is named after George H. Walden, who developed it jointly with a Ph.D. student, Sylvan M. Edmonds, at

Columbia University Columbia University (also known as Columbia, and officially as Columbia University in the City of New York) is a private research university in New York City. Established in 1754 as King's College on the grounds of Trinity Church in Manhatt ...

Preparation and use

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pink ...

wire is submerged in a solution of

silver nitrate Silver nitrate is an inorganic compound with chemical formula . It is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides. It was once called ''lunar causti ...

Dendritic Dendrite derives from the Greek word "dendron" meaning ( "tree-like"), and may refer to: Biology *Dendrite, a branched projection of a neuron * Dendrite (non-neuronal), branching projections of certain skin cells and immune cells Physical *Dendr ...

crystals of silver immediately form on the copper wire according to the following redox reaction: Cu + 2 Ag⁺ → Cu²⁺ + 2 Ag The

crystals are then removed from the copper wire, washed with

pure water Purified water is water that has been mechanically filtered or processed to remove impurities and make it suitable for use. Distilled water was, formerly, the most common form of purified water, but, in recent years, water is more frequently puri ...

to remove the

copper nitrate Copper(II) nitrate describes any member of the family of inorganic compounds with the formula Cu( NO3)2(H2O)x. The hydrates are blue solids. Anhydrous copper nitrate forms blue-green crystals and sublimes in a vacuum at 150-200 °C. Common ...

and the excess of

and packed in a small glass column. To use the reductor, the solution to be reduced is poured at the top of the glass tube, and then drawn through it. The reactive front progresses along the column as in

chromatography In chemical analysis, chromatography is a laboratory technique for the separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it through a system ( ...

and the extent of reduction reaches up to 100 % as the solution passes down the tube and the product becomes completely separated from the starting material.

Applications

The Walden reductor can be used to obtain chemical species in their low valence state if required for chemical analyses or to obtain small amounts of the compound in the appropriate form.

Preparation and use

Applications

See also

References

Further reading