Anomalous components of supercooled water expansivity, compressibility, and heat capacity (Cp and Cv) from binary formamide+water solution studies

M. Oguni, Charles Angell

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39 Citations (Scopus)

Abstract

Recently reported heat capacity studies of N2H 4+H2O and H2O2+H2O solutions, from which an anomalous component of the pure water behavior could be extracted by extrapolation, have been extended to a system NH 2CHO+H2O which has the chemical stability needed to permit expansivity and compressibility measurements as well. Data accurate to ±2% for each of these properties as well as for the heat capacity are reported. The expansivity data support almost quantitatively an earlier speculative separation of the bulk and supercooled water expansivity into a "normal" (or "background") part and an "anomalous" part, the latter part fitting a critical law αanom=A(T/T s-1) with exponent γ=1.0. According to the present analysis, the anomalous part of the expansivity which is always negative, yields T, in the range 225-228, γ in the range 1.28-1.0, depending on the choice of background extrapolation function. The normal contribution to the heat capacity obtained from the present work is intermediate in character to that from the previous two systems and leads to similar equation parameters. The normal contribution to the compressibility on the other hand is very different from that speculated earlier by Kanno and Angell and approximately verified by Conde et al. for ethanol-water solutions. The background component from the present analysis is ∼50% larger, with the result that the anomalous component, at least when values above 0 °C are included in the analysis, cannot be sensibly fitted to the critical point equation. The possible origin and interest content of these differences is discussed. Combination of the new thermodynamic data permit estimation of C v values for the solution, and by extrapolation, a normal C v component for water. The anomalous component of Cv for pure water obtained by difference has the form of a Shottky anomaly in contrast with the corresponding Cp component which diverges.

Original languageEnglish (US)
Pages (from-to)7334-7342
Number of pages9
JournalThe Journal of Chemical Physics
Volume78
Issue number12
StatePublished - 1982
Externally publishedYes

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Compressibility
compressibility
Specific heat
specific heat
Extrapolation
Water
water
extrapolation
Chemical stability
Ethanol
formamide
Thermodynamics
critical point
ethyl alcohol
exponents
anomalies
thermodynamics

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

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title = "Anomalous components of supercooled water expansivity, compressibility, and heat capacity (Cp and Cv) from binary formamide+water solution studies",
abstract = "Recently reported heat capacity studies of N2H 4+H2O and H2O2+H2O solutions, from which an anomalous component of the pure water behavior could be extracted by extrapolation, have been extended to a system NH 2CHO+H2O which has the chemical stability needed to permit expansivity and compressibility measurements as well. Data accurate to ±2{\%} for each of these properties as well as for the heat capacity are reported. The expansivity data support almost quantitatively an earlier speculative separation of the bulk and supercooled water expansivity into a {"}normal{"} (or {"}background{"}) part and an {"}anomalous{"} part, the latter part fitting a critical law αanom=A(T/T s-1)-γ with exponent γ=1.0. According to the present analysis, the anomalous part of the expansivity which is always negative, yields T, in the range 225-228, γ in the range 1.28-1.0, depending on the choice of background extrapolation function. The normal contribution to the heat capacity obtained from the present work is intermediate in character to that from the previous two systems and leads to similar equation parameters. The normal contribution to the compressibility on the other hand is very different from that speculated earlier by Kanno and Angell and approximately verified by Conde et al. for ethanol-water solutions. The background component from the present analysis is ∼50{\%} larger, with the result that the anomalous component, at least when values above 0 °C are included in the analysis, cannot be sensibly fitted to the critical point equation. The possible origin and interest content of these differences is discussed. Combination of the new thermodynamic data permit estimation of C v values for the solution, and by extrapolation, a normal C v component for water. The anomalous component of Cv for pure water obtained by difference has the form of a Shottky anomaly in contrast with the corresponding Cp component which diverges.",
author = "M. Oguni and Charles Angell",
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TY - JOUR

T1 - Anomalous components of supercooled water expansivity, compressibility, and heat capacity (Cp and Cv) from binary formamide+water solution studies

AU - Oguni, M.

AU - Angell, Charles

PY - 1982

Y1 - 1982

N2 - Recently reported heat capacity studies of N2H 4+H2O and H2O2+H2O solutions, from which an anomalous component of the pure water behavior could be extracted by extrapolation, have been extended to a system NH 2CHO+H2O which has the chemical stability needed to permit expansivity and compressibility measurements as well. Data accurate to ±2% for each of these properties as well as for the heat capacity are reported. The expansivity data support almost quantitatively an earlier speculative separation of the bulk and supercooled water expansivity into a "normal" (or "background") part and an "anomalous" part, the latter part fitting a critical law αanom=A(T/T s-1)-γ with exponent γ=1.0. According to the present analysis, the anomalous part of the expansivity which is always negative, yields T, in the range 225-228, γ in the range 1.28-1.0, depending on the choice of background extrapolation function. The normal contribution to the heat capacity obtained from the present work is intermediate in character to that from the previous two systems and leads to similar equation parameters. The normal contribution to the compressibility on the other hand is very different from that speculated earlier by Kanno and Angell and approximately verified by Conde et al. for ethanol-water solutions. The background component from the present analysis is ∼50% larger, with the result that the anomalous component, at least when values above 0 °C are included in the analysis, cannot be sensibly fitted to the critical point equation. The possible origin and interest content of these differences is discussed. Combination of the new thermodynamic data permit estimation of C v values for the solution, and by extrapolation, a normal C v component for water. The anomalous component of Cv for pure water obtained by difference has the form of a Shottky anomaly in contrast with the corresponding Cp component which diverges.

AB - Recently reported heat capacity studies of N2H 4+H2O and H2O2+H2O solutions, from which an anomalous component of the pure water behavior could be extracted by extrapolation, have been extended to a system NH 2CHO+H2O which has the chemical stability needed to permit expansivity and compressibility measurements as well. Data accurate to ±2% for each of these properties as well as for the heat capacity are reported. The expansivity data support almost quantitatively an earlier speculative separation of the bulk and supercooled water expansivity into a "normal" (or "background") part and an "anomalous" part, the latter part fitting a critical law αanom=A(T/T s-1)-γ with exponent γ=1.0. According to the present analysis, the anomalous part of the expansivity which is always negative, yields T, in the range 225-228, γ in the range 1.28-1.0, depending on the choice of background extrapolation function. The normal contribution to the heat capacity obtained from the present work is intermediate in character to that from the previous two systems and leads to similar equation parameters. The normal contribution to the compressibility on the other hand is very different from that speculated earlier by Kanno and Angell and approximately verified by Conde et al. for ethanol-water solutions. The background component from the present analysis is ∼50% larger, with the result that the anomalous component, at least when values above 0 °C are included in the analysis, cannot be sensibly fitted to the critical point equation. The possible origin and interest content of these differences is discussed. Combination of the new thermodynamic data permit estimation of C v values for the solution, and by extrapolation, a normal C v component for water. The anomalous component of Cv for pure water obtained by difference has the form of a Shottky anomaly in contrast with the corresponding Cp component which diverges.

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