Walden reductor
Encyclopedia
The Walden reductor is a reduction column filled with metallic silver
which can be used to reduce a metal ion in aqueous solution to a lower oxidation state
. It can be used e.g. to reduce UO22+ in U4+. The method is named after George H. Walden who developed together with a Ph.D. student Sylvan M. Edmonds at the Columbia University
.
is contacted with a solution of silver nitrate
. Dentritic
crystals of silver immediately forms on the copper wire according to the following redox reaction:
Cu + 2 Ag+ —> Cu2+ + 2 Ag
The silver
crystals are then removed from the copper wire, washed with pure water
to remove the copper nitrate and the excess of silver nitrate
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
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.
state if required for chemical analyses or to obtain small amounts of the compound in the appropriate form.
Other oxidizing reagents (opposite)
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
which can be used to reduce a metal ion in aqueous solution to a lower oxidation state
Oxidation state
In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...
. It can be used e.g. to reduce UO22+ in U4+. The method is named after George H. Walden who developed together with a Ph.D. student Sylvan M. Edmonds at the Columbia University
Columbia University
Columbia University in the City of New York is a private, Ivy League university in Manhattan, New York City. Columbia is the oldest institution of higher learning in the state of New York, the fifth oldest in the United States, and one of the country's nine Colonial Colleges founded before the...
.
Preparation and use
A wire of copperCopper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
is contacted with a solution of silver nitrate
Silver nitrate
Silver nitrate is an inorganic compound with chemical formula . This compound 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...
. Dentritic
Dendrite
Dendrites are the branched projections of a neuron that act to conduct the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project...
crystals of silver immediately forms on the copper wire according to the following redox reaction:
Cu + 2 Ag+ —> Cu2+ + 2 Ag
The silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
crystals are then removed from the copper wire, washed with pure water
Purified water
Purified water is water from any source that is physically processed to remove impurities. Distilled water and deionized water have been the most common forms of purified water, but water can also be purified by other processes including reverse osmosis, carbon filtration, microfiltration,...
to remove the copper nitrate and the excess of silver nitrate
Silver nitrate
Silver nitrate is an inorganic compound with chemical formula . This compound 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...
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
Chromatography
Chromatography is the collective term for a set of laboratory techniques for the separation of mixtures....
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 valenceValence (chemistry)
In chemistry, valence, also known as valency or valence number, is a measure of the number of bonds formed by an atom of a given element. "Valence" can be defined as the number of valence bonds...
state if required for chemical analyses or to obtain small amounts of the compound in the appropriate form.
See also
Other reducing reagents- Jones reductorJones reductorA Jones reductor is a device which can be used to reduce a metal ion in aqueous solution to a very low oxidation state. The active component is a zinc/mercury amalgam...
Other oxidizing reagents (opposite)
- Tollens' reagentTollens' reagentTollens' reagent is a chemical reagent most commonly used to determine whether a known carbonyl-containing compound is an aldehyde or a ketone. It is usually ammoniacal silver nitrate, but can also be other mixtures, as long as aqueous diamminesilver complex is present...
- Benedict's reagentBenedict's reagentBenedict's reagent is a chemical reagent named after an American chemist, Stanley Rossiter Benedict....
- Fehling's solutionFehling's solutionFehling's solution is a chemical test used to differentiate between water-soluble aldehyde and ketone functional groups, and as a test for monosaccharides. The test was developed by German chemist Hermann von Fehling in 1849.-Laboratory preparation:...