Studies in the lower temperature molten salts eutectics
Studies in the lower temperature molten salts eutectics
Molten acetamide, acetamide-LiCl and acetamide-KSCN eutectics have been used as solvents and reaction media. The first eutectic is a new system (13.4 mole% LiCl) melting at 46oC whereas the eutectic point of the second was redetermined as 26oC at 26.3 mole% KSCN. These melting points were lowered to 38oC and 16oC respectively when heated above a critical temperature (75 and 50oC) and interpreted in terms of structural changes from trigonal to orthohombic crystal forms of acetamide. The density of both eutectics was measured and found to be a linear function of temperature. All three lower temperature melts proved to be good solvents for transition metal and other compounds and gave electronic absorption spectra of particular interest due to the presence of several competing ligands in solution (e.g. in acetamide-KSCN eutectic, S and N bonded thiocyanate as well as the oxygen of acetamide). VO(IV), Cr(III), Mn(II), Fe(II), and Ni(II) formed stable solutions in all three melts. Octahedral coordination was always found for VO(IV), Cr(III) and Ni(II), but Co(II) was distorted octahedral, or octrahedral-tetrahedral in molten acetamide depending on the temperature and concentration but tetrahedral in the eutectics. Fe(III) was six coordinated in molten acetamide and in acetamide-KSCN eutectic, but tetrahedral in acetamide-LiCl eutectic. Mn(II) also tetrahedral in the latter but both octahedral-tetrahedral complexes were indicated in molten acetamide and acetamide-KSCN eutectic. Distorted octahedra were found for Ti(III), V(III) and Cr(II) solutes, with partial oxidation of the latter in acetamide-KSCN eutectic. Both Cr(VI) and Co(III) cations were reduced, the relative reducing power being acetamide-KSCN > acetamide-LiCl > acetamide. Ligand exchange reactions were observed for all cobalt(III) ethylene diamine complexes in the three melts. Distorted octahedral coordination was also found for Cu(II) in molten acetamide and in acetamide-KSCN eutectic (though in the latter reduction to Cu(I) with oxidation of thiocyanate to parathiocyanogen, (SCN)x, was observed). Eight acid base indicators were readily soluble and stable in acetamide-KSCN eutectic and were used in some acid-base reactions (e.g. Na2) with K2S2O7). Finally the reaction of some oxidizing agents (Ce(SO4)2, K2S2O8, I2, KIO4, KIO3, KCIO3, I2O5 and KMnO(4) were studied in acetamide-KSCN eutectic which showed a reducing power comparable to that of pure molten potassium thiocyanate.
University of Southampton
1989
Issac, Ibrahim Youhanna
(1989)
Studies in the lower temperature molten salts eutectics.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Molten acetamide, acetamide-LiCl and acetamide-KSCN eutectics have been used as solvents and reaction media. The first eutectic is a new system (13.4 mole% LiCl) melting at 46oC whereas the eutectic point of the second was redetermined as 26oC at 26.3 mole% KSCN. These melting points were lowered to 38oC and 16oC respectively when heated above a critical temperature (75 and 50oC) and interpreted in terms of structural changes from trigonal to orthohombic crystal forms of acetamide. The density of both eutectics was measured and found to be a linear function of temperature. All three lower temperature melts proved to be good solvents for transition metal and other compounds and gave electronic absorption spectra of particular interest due to the presence of several competing ligands in solution (e.g. in acetamide-KSCN eutectic, S and N bonded thiocyanate as well as the oxygen of acetamide). VO(IV), Cr(III), Mn(II), Fe(II), and Ni(II) formed stable solutions in all three melts. Octahedral coordination was always found for VO(IV), Cr(III) and Ni(II), but Co(II) was distorted octahedral, or octrahedral-tetrahedral in molten acetamide depending on the temperature and concentration but tetrahedral in the eutectics. Fe(III) was six coordinated in molten acetamide and in acetamide-KSCN eutectic, but tetrahedral in acetamide-LiCl eutectic. Mn(II) also tetrahedral in the latter but both octahedral-tetrahedral complexes were indicated in molten acetamide and acetamide-KSCN eutectic. Distorted octahedra were found for Ti(III), V(III) and Cr(II) solutes, with partial oxidation of the latter in acetamide-KSCN eutectic. Both Cr(VI) and Co(III) cations were reduced, the relative reducing power being acetamide-KSCN > acetamide-LiCl > acetamide. Ligand exchange reactions were observed for all cobalt(III) ethylene diamine complexes in the three melts. Distorted octahedral coordination was also found for Cu(II) in molten acetamide and in acetamide-KSCN eutectic (though in the latter reduction to Cu(I) with oxidation of thiocyanate to parathiocyanogen, (SCN)x, was observed). Eight acid base indicators were readily soluble and stable in acetamide-KSCN eutectic and were used in some acid-base reactions (e.g. Na2) with K2S2O7). Finally the reaction of some oxidizing agents (Ce(SO4)2, K2S2O8, I2, KIO4, KIO3, KCIO3, I2O5 and KMnO(4) were studied in acetamide-KSCN eutectic which showed a reducing power comparable to that of pure molten potassium thiocyanate.
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Published date: 1989
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Local EPrints ID: 461607
URI: http://eprints.soton.ac.uk/id/eprint/461607
PURE UUID: a2a836b9-6bb8-4ddd-bddb-e83560261d4a
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Date deposited: 04 Jul 2022 18:50
Last modified: 04 Jul 2022 18:50
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Author:
Ibrahim Youhanna Issac
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