Raman spectral studies of solutions at elevated temperatures and pressures.13. Sodium formate – water

1993 ◽  
Vol 71 (10) ◽  
pp. 1728-1733 ◽  
Author(s):  
Richard J. Bartholomew ◽  
Donald E. Irish
Keyword(s):  
Raman Spectra ◽  
Elevated Temperatures ◽  
Sodium Formate ◽  
Fermi Resonance ◽  
Spectral Studies ◽  
Coupling Constant ◽  
Ambient Conditions ◽  
Modes Of Vibration ◽  
Resonance Doublet ◽  
Raman Spectral

Raman spectra of the formate anion in water (H2O and D2O) have been measured for four concentrations under ambient conditions and for two concentrations at temperatures ranging from 49 to 239 °C and a pressure of 10 MPa. Five of the six fundamental modes of vibration are polarized. This result is inconsistent with C2ν symmetry. The Fermi resonance doublet clearly results from the interaction of 2ν5 and ν1. The latter mode decreases in frequency as the temperature rises, thus increasing the coupling and hence the intensity of the 2ν5 component. The coupling constant, W, and the positions of the unperturbed bands [Formula: see text] and [Formula: see text] have been calculated. No evidence to support a bifurcated structure for the solvated anion was found.

scholarly journals Raman Spectral Studies of Aqueous Acidic Pyrazine Solutions

1995 ◽  
Vol 50 (2-3) ◽  
pp. 274-282 ◽  
Author(s):  
Alexandre G. Brolo ◽  
Donald E. Irish
Keyword(s):  
Raman Spectra ◽  
Species Distribution ◽  
Spectral Studies ◽  
Acidic Media ◽  
Distribution Diagram ◽  
Protonated Forms ◽  
Species Distribution Diagram ◽  
Diprotonated Form ◽  
High Concentrations ◽  
Raman Spectral

Abstract Raman spectra of aqueous pyrazine have been investigated in acidic media: HCl from pH = 4 up to 11 M; HCLO4 from 0.1 M to 12 M; H2SO4 form 0.1 M to 18 M. From observation of the shifts of the bands from neutral solutions, it has been possible to identify bands uniquely characteristic of unprotonated pyrazine and its two protonated forms. The diprotonated form was only observed for high concentrations of HCLO4 and H2SO4. From bandfitting of the spectral contours it has been possible to construct the species distribution diagram and estimate the pK values. Raman bands of the three species have been identified and assigned. The results are used to explain an unassigned band at 1235 cm-1, reported by several authors, in SERS from pyrazine on silver and gold electrodes.

Vibrational Spectral Studies of Solutions at Elevated Temperatures and Pressures. IV. Raman Spectra of Aqueous Zinc Nitrate Solutions

1983 ◽  
Vol 37 (1) ◽  
pp. 50-55 ◽  
Author(s):  
D. E. Irish ◽  
T. Jarv
Keyword(s):  
Raman Spectra ◽  
Elevated Temperatures ◽  
Nitrate Solution ◽  
Ion Association ◽  
Outer Sphere ◽  
Solvation Shell ◽  
Zinc Nitrate ◽  
Spectral Studies ◽  
Tetrahedral Configuration ◽  
Nitrate Ion

Raman spectra of 5.196 m aqueous zinc nitrate solution have been measured at a pressure of 11 MPa and temperatures ranging from 25 to 300°C. A band at 386 cm−1, assigned to the hexaaquazinc(II) cation, decreases in intensity and increases in freqeuncy as the temperature rises. These observations are consistent with the replacement of water molecules in the primary solvation shell of Zn2+ by a nitrate ion. Changes in the spectrum of nitrate ion support this interpretation. Evidence is also presented which suggests that the octahedral configuration around Zn2+ is being changed to a tetrahedral configuration. Estimates are made of the populations of inner sphere and outer sphere nitrate; from the plots of log Qm vs 1/ T estimates are made of ΔH and Δ S for the ion association. The plots are remarkably linear over 275 degrees of temperature.

Vibrational spectral studies of solutions at elevated temperatures and pressures. 11. A Raman spectral study of aqueous iron(III) chloride solutions between 25 and 300 °C

1989 ◽  
Vol 67 (3) ◽  
pp. 517-524 ◽  
Author(s):  
Katsuo Murata ◽  
Donald E. Irish ◽  
Gerald E. Toogood
Keyword(s):  
Raman Spectroscopy ◽  
Dielectric Constant ◽  
Dominant Species ◽  
Elevated Temperatures ◽  
Spectral Studies ◽  
Iron Species ◽  
Chloride Solutions ◽  
Increasing Temperature ◽  
Raman Spectral ◽  
Temperature Factors

The Raman spectra of acidified aqueous iron(III) chloride solutions have been measured between 25 and 300 °C. When Fe3+ concentrations are in the range 0.75 to 1.0 mol kg−1 and Cl−/Fe3+ ratios, R, in the range 3 to 9.5, the dominant species at 25 °C is trans-[Fe(H2O)4Cl2]+; at 300 °C the sole iron-containing species is tetrahedral [Formula: see text]. Conversion of [Fe(H2O)4Cl2]+ into [Formula: see text] appears not to involve intermediate iron species. In the presence of excess chloride the reaction [Formula: see text] is presumed to occur; ΔH for this reaction has been estimated as +65 ± 8 kJ mol−1. In addition to increasing temperature, factors which favour [Formula: see text] over other iron species include increasing acidity, increasing R, and decreasing dielectric constant. Keywords: high temperature aqueous solutions, iron(III) chloride, Raman spectroscopy.

Vibrational Spectral Studies of Solutions at Elevated Temperatures and Pressures. III. A Furnace Assembly for Raman Spectral Studies to 300°C and 15 MPa

1982 ◽  
Vol 36 (2) ◽  
pp. 137-140 ◽  
Author(s):  
D. E. Irish ◽  
T. Jarv ◽  
C. I. Ratcliffe
Keyword(s):  
High Temperature ◽  
Aqueous Solutions ◽  
Elevated Temperatures ◽  
Chemical Processes ◽  
Spectral Studies ◽  
Raman Spectral

The design of a furnace assembly for maintaining aqueous solutions at temperatures up to 300°C and controlled pressures of up to 15 MPa is described. The apparatus is being used to monitor the chemical processes taking place in high-temperature aqueous solutions. Spectra of the Zn(NO3)2/H2O system and the HCl/H2O system are presented as examples.

Vibrational spectral studies of solutions at elevated temperatures and pressures. VII. Raman spectra and dissociation of nitric acid

1985 ◽  
Vol 63 (12) ◽  
pp. 3521-3525 ◽  
Author(s):  
C. I. Ratcliffe ◽  
D. E. Irish
Keyword(s):  
Hydrogen Bonding ◽  
Nitric Acid ◽  
Raman Spectra ◽  
Exploratory Study ◽  
Elevated Temperatures ◽  
Spectral Studies ◽  
Acid Solutions ◽  
Concentration Increase ◽  
Degree Of Dissociation ◽  
Nitric Acid Solutions

An exploratory study of the Raman spectra of nitric acid solutions up to 250 °C has been undertaken. The decrease in the frequencies of the νN—(OH) and δNO2 bands of HNO3 as temperature and concentration increase have been interpreted in terms of the reduced strength of hydrogen bonding. Approximate values of the degree of dissociation α have been determined and show that nitric acid is a very much weaker acid at high temperatures.

The polymorphism of alkali metal formates. Part 4. A Raman study of the phase transition in KHCOO

1991 ◽  
Vol 69 (11) ◽  
pp. 1774-1780 ◽  
Author(s):  
A. M. Heyns ◽  
K.-J. Range ◽  
K. Müller
Keyword(s):  
Phase Transition ◽  
Phase I ◽  
Raman Spectra ◽  
Orthorhombic Phase ◽  
Fermi Resonance ◽  
Theoretical Treatment ◽  
Ambient Conditions ◽  
Definite Structure ◽  
Raman Study ◽  
Intramolecular Motions

KHCOO II is orthorhombic at ambient conditions and it is shown that traces of moisture affect the polymorphism of these very hygroscopic crystals. Dry KHCOO II transforms into phase I at 417 K (144 °C), and this phase can be supercooled to room temperature, remaining metastable for several days before transforming back to the orthorhombic phase II. The Raman spectra of phases I and II, as well as of supercooled phase I, are reported in the present study. The absence of some prominent translational modes in the Raman spectra of KHCOO II, compared to NaHCOO II, can be explained on the basis of a group-theoretical treatment. From the temperature dependence of the linewidths of various Raman-active librational and internal modes, activation energies are obtained for intramolecular motions of the formate ions. Fermi resonance occurs between the overtone of the bending mode 2ν5 and the C—H stretching mode ν1 in KHCOO II and the coupling constant W increases with temperature. The Raman and X-ray data show that KHCOO I is structurally different from NaCHOO I, but it is not possible to assign a definite structure to this phase on the basis of a Raman spectrum alone. Key words: Potassium formate, phase transition, Raman spectra.

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