Some aspects of the chemistry of molten nitrites
Some aspects of the chemistry of molten nitrites
The Lux-Flood acid-base behaviour and oxidation-reduction properties of nitrite melts were investigated. These studies showed the nitrite melt to be a moderately strong base and also to exhibit both reducing and oxidizing properties.
Seven vanadium compounds were studied, potassium disulphatovanadate (III), vanadyl (IV) sulphate and vanadium (IV) oxide being initially oxidized to metavanadate while vanadium pentoxide initially reacted to give both metavanadate and vanadium (IV) oxide. Metavanadate then reacted further at 300°C to yield orthovanadate which was found to catalyze the decomposition of nitrite melt.
Sodium cobaltinitrite underwent cation exchange in nitrite eutectics with melting points below its decomposition temperature (170°C) to yield potassium cobaltinitrite as an Intermediate which decomposed at 220°C to form Co3O4. However, in the higher melting Na/KNO2 (220°C) considerable thermal decomposition of sodium cobaltinitrite took place below the melting point. Hexamminecobalt (111) chloride initially decomposed in nitrite eutectics, producing cobalt (II) chloride which reacted with the melt to form potassium cobaltinitrite.
The electronic spectra of nickel (II) and copper (II) in molten Li/KNO2 were obtained. The spectrum of nickel (II) complex was consistent with a regular octahedral coordination suggested to be [Ni(NO2)3(ONO)3]4-. The reflectance spectra for the solid showed a change in the nature of coordination which suggested the formation of [Ni(NO2)4(ONO)2]4-. From the spectrum of copper (II) a distorted octahedral complex, [Cu(NO2)4(ONO)2]4- is suggested.
The behaviours of six lead compounds as well as metallic lead in Na/KNO2 eutectic were studied. Metallic lead was only surface oxidized and lead monoxide was inert, whereas lead dioxide oxidized the nitrite ion to nitrate ion. Red lead, Pb3O4, reacted with the nitrite melt, forming lead monoxide. Based on thermogravimetric analysis, the reaction is suggested to take place through the formation of both Pb(NO2)2 and Pb(NO2)4. Lead (II) nitrite decomposed stepwise in a nitrite melt to yield lead monoxide as the final product. The compounds 2Pb(NO2)2. PbO and Pb(NO2)2. 2PbO are proposed as intermediates. Both lead nitrate and lead chloride underwent anion exchange at and slightly below the melting point to form lead (II) nitrite.
The reactions of sodium orthotungstate, tungsten trioxide, tungsten hexacarbonyl and metallic tungsten were investigated. Sodium orthotungstate was inert, whereas tungsten trioxide reacted below the melting point forming orthotungstate. Tungsten metal acted as a reducing agent, orthotungstate, nitrogen, nitrous oxide and nitric oxide being formed according to the conditions. Tungsten hexacarbonyl underwent sublimation and appeared to be unreactive in the melt. Zirconium metal did not react with a nitrite melt up to 400°C, even on the addition of sodium peroxide. Potassium permanganate reacted to form the unstable, green manganate (VI) ion which then decomposed to form manganate (IV).
The stoichiometries of the Lux-Flood acid-base reactions of (NaPO3), Na3(PO3)3, Na4(PO3)4, NK4P2O7, Na5P3O10 and P4O10 were studied. All these phosphate compounds, except pyrophosphate, initially depolymerized below the melting point to pyrophosphate. The latter then degraded further at 300°C to produce orthophosphate.
The reactions of peroxide ion with a nitrite melt was investigated and the equilibrium constant of the reaction
O2-2 + NO-2 = NO-3 + O2-
was determined to be ≃ 0.1 in a zirconium crucible. The attack on a platinum crucible by the presence of peroxide ion in a nitrite melt was found to produce platinum (IV) oxide and the corrosive species is suggested to be the peroxonitrite ion.
University of Southampton
Al-omer, Sabah Saleh
9d9eaa3d-9733-4547-95c2-f5bb848b3acc
December 1973
Al-omer, Sabah Saleh
9d9eaa3d-9733-4547-95c2-f5bb848b3acc
Kerridge, David H.
8ac6422a-c915-41e0-b573-33311cafb21a
Al-omer, Sabah Saleh
(1973)
Some aspects of the chemistry of molten nitrites.
University of Southampton, Doctoral Thesis, 220pp.
Record type:
Thesis
(Doctoral)
Abstract
The Lux-Flood acid-base behaviour and oxidation-reduction properties of nitrite melts were investigated. These studies showed the nitrite melt to be a moderately strong base and also to exhibit both reducing and oxidizing properties.
Seven vanadium compounds were studied, potassium disulphatovanadate (III), vanadyl (IV) sulphate and vanadium (IV) oxide being initially oxidized to metavanadate while vanadium pentoxide initially reacted to give both metavanadate and vanadium (IV) oxide. Metavanadate then reacted further at 300°C to yield orthovanadate which was found to catalyze the decomposition of nitrite melt.
Sodium cobaltinitrite underwent cation exchange in nitrite eutectics with melting points below its decomposition temperature (170°C) to yield potassium cobaltinitrite as an Intermediate which decomposed at 220°C to form Co3O4. However, in the higher melting Na/KNO2 (220°C) considerable thermal decomposition of sodium cobaltinitrite took place below the melting point. Hexamminecobalt (111) chloride initially decomposed in nitrite eutectics, producing cobalt (II) chloride which reacted with the melt to form potassium cobaltinitrite.
The electronic spectra of nickel (II) and copper (II) in molten Li/KNO2 were obtained. The spectrum of nickel (II) complex was consistent with a regular octahedral coordination suggested to be [Ni(NO2)3(ONO)3]4-. The reflectance spectra for the solid showed a change in the nature of coordination which suggested the formation of [Ni(NO2)4(ONO)2]4-. From the spectrum of copper (II) a distorted octahedral complex, [Cu(NO2)4(ONO)2]4- is suggested.
The behaviours of six lead compounds as well as metallic lead in Na/KNO2 eutectic were studied. Metallic lead was only surface oxidized and lead monoxide was inert, whereas lead dioxide oxidized the nitrite ion to nitrate ion. Red lead, Pb3O4, reacted with the nitrite melt, forming lead monoxide. Based on thermogravimetric analysis, the reaction is suggested to take place through the formation of both Pb(NO2)2 and Pb(NO2)4. Lead (II) nitrite decomposed stepwise in a nitrite melt to yield lead monoxide as the final product. The compounds 2Pb(NO2)2. PbO and Pb(NO2)2. 2PbO are proposed as intermediates. Both lead nitrate and lead chloride underwent anion exchange at and slightly below the melting point to form lead (II) nitrite.
The reactions of sodium orthotungstate, tungsten trioxide, tungsten hexacarbonyl and metallic tungsten were investigated. Sodium orthotungstate was inert, whereas tungsten trioxide reacted below the melting point forming orthotungstate. Tungsten metal acted as a reducing agent, orthotungstate, nitrogen, nitrous oxide and nitric oxide being formed according to the conditions. Tungsten hexacarbonyl underwent sublimation and appeared to be unreactive in the melt. Zirconium metal did not react with a nitrite melt up to 400°C, even on the addition of sodium peroxide. Potassium permanganate reacted to form the unstable, green manganate (VI) ion which then decomposed to form manganate (IV).
The stoichiometries of the Lux-Flood acid-base reactions of (NaPO3), Na3(PO3)3, Na4(PO3)4, NK4P2O7, Na5P3O10 and P4O10 were studied. All these phosphate compounds, except pyrophosphate, initially depolymerized below the melting point to pyrophosphate. The latter then degraded further at 300°C to produce orthophosphate.
The reactions of peroxide ion with a nitrite melt was investigated and the equilibrium constant of the reaction
O2-2 + NO-2 = NO-3 + O2-
was determined to be ≃ 0.1 in a zirconium crucible. The attack on a platinum crucible by the presence of peroxide ion in a nitrite melt was found to produce platinum (IV) oxide and the corrosive species is suggested to be the peroxonitrite ion.
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Published date: December 1973
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Local EPrints ID: 511799
URI: http://eprints.soton.ac.uk/id/eprint/511799
PURE UUID: 0f56aafd-a818-44b9-91fa-7fc41038ef54
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Date deposited: 03 Jun 2026 16:32
Last modified: 03 Jun 2026 16:54
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Author:
Sabah Saleh Al-omer
Thesis advisor:
David H. Kerridge
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