The data gap in solution chemistry: The ideal glass transition puzzle

1970 ◽  
Vol 47 (8) ◽  
pp. 583 ◽  
Author(s):  
C. A. Angell
Keyword(s):  
Glass Transition ◽  
Solution Chemistry ◽  
Data Gap ◽  
The Ideal

The Formation of Green Rust and Its Transformation to Lepidocrocite

Clay Minerals ◽  
1994 ◽  
Vol 29 (1) ◽  
pp. 87-92 ◽  
Author(s):  
U. Schwertmann ◽  
H. Fechter
Keyword(s):  
Solid State ◽  
Reaction Rate ◽  
Green Rust ◽  
Solution Chemistry ◽  
Subsequent Transformation ◽  
Constant Ph ◽  
Temperature Constant ◽  
A Minor ◽  
Complete Transformation ◽  
The Ideal

AbstractThe formation of FeII,III hydoxy salts (green rusts) from FeII sulphate and chloride solutions and their transformation to lepidocrocite, γ-FeOOH, was studied at ambient temperature, constant pH of ∼7.0 and under controlled air flow. The formation of green rust and its subsequent transformation to lepidocrocite could be distinguished by the reaction rate and solution chemistry. The SO42− and Cl− concentrations in solution attain a minimum at the break between the two reaction steps and are completely restored to their initial values after complete transformation to lepidocrocite. While the green rust is being formed, its FeII/FeIII ratio shows a minor decrease and its FeIII/anion ratio a minor increase. These ratios, however, deviate from the ideal pyroaurite-type structure (M2+/M3+ = 3; M3+/A− = 1; M: metal; A−: anion) and possibilities to accommodate this deviation are discussed. A period during which no protons were produced (i.e. no base consumed) was found to separate the two reactions in the chloride, but not in the sulphate system. During this period a partial solid state oxidation of the green rust took place, leading to its destabilization and eventual decomposition.

Temperature and Pressure Dependence of the Electrical Conductivity of Two Tetraalkylammonium Tetraalkylborate Salts

1999 ◽  
Vol 52 (5) ◽  
pp. 373 ◽  
Author(s):  
Nashiour Rohman ◽  
Sekh Mahiuddin ◽  
Raymond Aich ◽  
Klaus Tödheide
Keyword(s):  
Electrical Conductivity ◽  
Glass Transition ◽  
Transition Temperature ◽  
Pressure Dependence ◽  
Empirical Equation ◽  
Electrical Conductivities ◽  
Temperature And Pressure ◽  
Isothermal Equation ◽  
Key Parameter ◽  
The Ideal

Electrical conductivities of molten trimethylpentylammonium triethyloctylborate (N1115B2228) and triethylpentylammonium triethylpentylborate (N2225B2225) were measured as functions of temperature (c. 293 · 15–383 · 15 K) and pressure (from 1 bar to 5 kbar). Analysis of the temperature dependence of the electrical conductivity was made by using the Vogel–Tammann–Fulcher equation, κ = Aexp[ – B/(T – T0)]. The empirical nature of the pressure dependence of the B and T0 parameters has revealed the possibility of obtaining an isothermal equation to explain the pressure dependence of the electrical conductivity. Accordingly, an empirical equation of the form κ = a′exp(b′ P+c′ P2) has been found to describe the pressure dependence of the electrical conductivity. The ideal glass transition temperature, T0, is the key parameter in controlling the pressure dependence of the electrical conductivity for both systems under study.

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