Silver(I,III) oxide
| Names | |
|---|---|
| IUPAC name
silver(I,III) Oxide | |
| Other names
silver peroxide, argentic oxide, silver suboxide, divasil | |
| Identifiers | |
1301-96-8  | |
| Properties | |
| AgO Ag2O.Ag2O3 | |
| Molar mass | 123.87 g/mol |
| Appearance | grey-black powder diamagnetic |
| Density | 7.48 g/cm3 |
| Melting point | >100 °C, decomposition |
| .0027 g/100 mL | |
| Solubility | soluble in alkalis |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
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| Infobox references | |
Silver(I,III) oxide is the inorganic compound with the formula Ag4O4. It is a component of silver oxide-zinc alkaline batteries. It can be prepared by the slow addition of a silver(I) salt to a persulfate solution e.g. AgNO3 to a Na2S2O8 solution.[1] It adopts an unusual structure, being a mixed-valence compound.[2] It is a dark brown solid that decomposes with evolution of O2 in water. It dissolves in concentrated nitric acid to give brown solutions containing the Ag2+ ion.[3]
Structure
Although its empirical formula, AgO, suggests that silver is in the +2 oxidation state in this compound, AgO is in fact diamagnetic. X-ray diffraction studies show that the silver atoms adopt two different coordination environments, one having two collinear oxide neighbours and the other four coplanar oxide neighbours.[1] AgO is therefore formulated as AgIAgIIIO2[4] or Ag2O·Ag2O3. It is being a 1:1 molar mixture of silver(I) oxide, Ag2O, and silver(III) oxide, Ag2O3. It has previously been called silver peroxide, which is incorrect since does not contain the peroxide ion, O22−.
Preparation
US patent 4003757 (Lux and Chobanov) describes one method for preparing this oxide (then called Ag(II)-oxide) in a form suitable for batteries and gives the following example:
In 1.5 liters of aqueous solution containing 150 grams of sodium hydroxide, 65 grams of silver powder are suspended with continuous stirring. The silver powder has a density of approximately 1.6 grams per cubic centimeter. Its grain size distribution is: 52% under 10 microns; 33% 10 microns to 30 microns, 15% above 30 microns.
The liquid is then heated to about 85° C. Upon reaching this temperature, a total of 200 grams of potassium peroxidisulfate (K2S2O8) in portions of about 40 grams each is added at intervals of, for example, 1 hour. After addition of the final portion of oxidant, stirring is continued for 3 hours. The product is then filtered, washed to free it of alkali substances, dried at a temperature of approximately 80° C and reduced to particle form.
The foregoing yields approximately 73 grams of silver-(I,III)-oxide with more than 95% content of pure silver-(I,III)-oxide. The silver oxide produced is characterized by high thermodynamic stability, low internal discharge and consequent long shelf life. The rate of gas evolution of their products in 18% NaOH is below 1 microliter per gram-hour at room temperature. This stability is attributable to the fact that the process embodying the invention produces single crystals of exceptionally regular shape and monoclinic form.
References
- 1 2 Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
- ↑ David Tudela "Silver(II) Oxide or Silver(I,III) Oxide?" J. Chem. Educ., 2008, volume 85, p 863. doi: 10.1021/ed085p863
- ↑ Peter Fischer, Martin Jansen "Electrochemical Syntheses of Binary Silver Oxides" 1995, vol. 30, pp. 50–55. doi:10.1002/9780470132616.ch11
- ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9. p. 1181.
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