Nitric/Nitrous Acid Equilibria in Supercritical Water

Chlistunoff, Jerzy; Ziegler, Kirk J.; Lasdon, Leon S.; Johnston, Keith P.

doi:10.1021/jp983745o

Cited by 56 publications

(33 citation statements)

References 77 publications

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“…The excellent agreement with the previous work on acetic acid by Mesmer et al (1989) confirms findings by Johnston (1994, 1997), Ryan et al (1997), and Chlistunoff et al (1999) that accurate ionization constants can be obtained with colorimetric indicators under hydrothermal conditions (see also Méndez De Leo et al, 2002). The combination of thermally stable colorimetric indicators with high-pressure flow cells and UV-visible spectrophotometry provides a fast and accurate method for determining dissociation constants for weak acids and bases at extremes of temperature and pressure.…”

Section: Discussionsupporting

confidence: 87%

“…The flow system is similar to that developed by Chlistunoff et al (1999) and was described in a previous paper (Trevani et al, 2001). The cell and injection system are illustrated schematically in Figure 2.…”

Section: Apparatusmentioning

confidence: 99%

“…Recent work at the University of Texas (Austin) has identified five thermally stable colorimetric pH indicators, which have been used with success in UV-visible spectrophotometric flow cells to determine ionization constants of simple acids and bases at temperatures as high as 400°C (Ryan et al, 1997;Johnston, 1994, 1997;Chlistunoff et al, 1999). To apply this method to the amino acids, we have employed a high-temperature, high-pressure spectrophotometric flow system described in a previous paper by Trevani et al (2001).…”

Section: Introductionmentioning

confidence: 99%

“…To apply this method to the amino acids, we have employed a high-temperature, high-pressure spectrophotometric flow system described in a previous paper by Trevani et al (2001). The procedure, which is similar in concept to that developed by Chlistunoff et al (1999), involves preparing buffer solutions of the amino acid, with its sodium and trifluoromethanesulfonate ("triflate") salts, which are pumped through the cell at elevated temperatures. The pH is determined from the spectrum of a trace concentration of the appropriate colorimetric pH indicator which has been added to the buffer solution.…”

Section: Introductionmentioning

confidence: 99%

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Ionization constants of aqueous amino acids at temperatures up to 250°C using hydrothermal pH indicators and UV-visible spectroscopy: Glycine, α-alanine, and proline

Clarke

Collins

Roberts

et al. 2005

Geochimica et Cosmochimica Acta

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Abstract-Ionization constants for several simple amino acids have been measured for the first time under hydrothermal conditions, using visible spectroscopy with a high-temperature, high-pressure flow cell and thermally stable colorimetric pH indicators. This method minimizes amino acid decomposition at high temperatures because the data can be collected rapidly with short equilibration times. The first ionization constant for proline and ␣-alanine, K a,COOH , and the first and second ionization constants for glycine, K a,COOH and K a,NH4ϩ , have been determined at temperatures as high as 250°C. Values for the standard partial molar heat capacity of ionization, ⌬ r C p o , COOH and ⌬ r C p o , NH4ϩ , have been determined from the temperature dependence of ln (K a,COOH ) and ln (K a,NH4ϩ ). The methodology has been validated by measuring the ionization constant of acetic acid up to 250°C, with results that agree with literature values obtained by potentiometric measurements to within the combined experimental uncertainty.We dedicate this paper to the memory of Dr. Donald Irish (1932-2002 of the University of Waterloofriend and former supervisor of two of the authors (R.J.B. and P.R.T.).

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Section: Discussionsupporting

confidence: 87%

Section: Apparatusmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ionization constants of aqueous amino acids at temperatures up to 250°C using hydrothermal pH indicators and UV-visible spectroscopy: Glycine, α-alanine, and proline

Clarke

Collins

Roberts

et al. 2005

Geochimica et Cosmochimica Acta

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“…Details of the SCF experimental set-up have been described elsewhere 16,37 . Ge nanowires were synthesized using two procedures, an injection method and by batch reaction.…”

Section: Ge Nanowire Synthesis In Sc-co2mentioning

confidence: 99%

Germanium Nanowire Synthesis from Fluorothiolate-Capped Gold Nanoparticles in Supercritical Carbon Dioxide

et al. 2010

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Access to the full text of the published version may require a subscription. Differences in the ligand conformations on the surface of the Au nanoparticles and phase separation of the fluorocarbon/CO2 and hydrocarbon/toluene systems, gave rise to greater steric stabilisation of 2 the fluorous-capped Au nanoparticles in CO2, resulting in small diameter nanowires with a relatively narrow size distribution. Electrical analysis of the nanowires showed them to be p-type (hole) Rightssemiconductors.

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Direct observation of polyvinylchloride degradation in water at temperatures up to 500°C and at pressures up to 700 MPa

Nagai

Smith

Inomata

et al. 2007

J of Applied Polymer Sci

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Degradation of polyvinylchloride (PVC) in high-temperature and supercritical water was studied with a hydrothermal diamond anvil cell to determine phase change characteristics of the reacting polymer with respect to water density. During the reaction period of 500 s, at temperatures between 400 and 5008C and at water densities from 0 to 930 kg/m 3 , PVC particles exhibited clearly defined spreading on the anvil surface that was defined as spread time, S t . The spread times decreased with increasing temperature and the values increased with increasing water density. Analysis of the residues with infrared spectroscopy showed the presence of both polyenes and polyols, whose formation was correlated with water density.From the analyses, nucleophilic substitution of PVC in water was found to be promoted at low temperatures ($ 4008C) and high water densities (>830 kg/m 3 ), whereas the ionic chain dechlorination was promoted at high temperatures (> $ 4508C) and low water densities ($ 750 kg/ m 3 ). A reaction pathway is proposed that shows À ÀOH nucleophilic substitution in competition with ionic chain reaction for dechlorination both of which vary with water density.

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Nitric/Nitrous Acid Equilibria in Supercritical Water

Cited by 56 publications

References 77 publications

Ionization constants of aqueous amino acids at temperatures up to 250°C using hydrothermal pH indicators and UV-visible spectroscopy: Glycine, α-alanine, and proline

Ionization constants of aqueous amino acids at temperatures up to 250°C using hydrothermal pH indicators and UV-visible spectroscopy: Glycine, α-alanine, and proline

Germanium Nanowire Synthesis from Fluorothiolate-Capped Gold Nanoparticles in Supercritical Carbon Dioxide

Direct observation of polyvinylchloride degradation in water at temperatures up to 500°C and at pressures up to 700 MPa

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