Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

Heat capacities and the two-point scaling analysis of short-chain surfactant solutions

Wasiak, M., Kunz, W., Piekarski, H.
Fluid Phase Equilib. 2013, 358, 78-82
ABSTRACT
The apparent molar heat capacities of two short-chain surfactants (C6TAB and C8TAB) aqueous solutions were determined at four temperatures. For the hexyltrimethylammonium bromide no structural transition was observed. For the octyltrimethylammonium bromide a maximum of the apparent molar heat capacity was observed, which corresponds to the monomer to micelle transition. The two-point scaling theory, that describes the thermodynamics of the system, which can appear in two phases in the vicinity of critical point, was applied to analyse this system. The critical molalities and critical indices were obtained. Comparison of these values with those previously reported for other similar systems allowed to relate them with structure changes in the solution.
Compounds
# Formula Name
1 C9H22BrN hexyltrimethylammonium bromide
2 C11H26BrN octyl trimethyl ammonium bromide
3 H2O water
Datasets
The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type Compound-# Property Variable Constraint Phase Method #Points
  • POMD
  • 3
  • Molar heat capacity at constant pressure, J/K/mol ; Liquid
  • Temperature, K; Liquid
  • Pressure, kPa; Liquid
  • Liquid
  • Large sample (1 g) DSC
  • 8
  • POMD
  • 3
  • Mass density, kg/m3 ; Liquid
  • Pressure, kPa; Liquid
  • Temperature, K; Liquid
  • Liquid
  • Vibrating tube method
  • 1
  • POMD
  • 1
  • 3
  • Molar heat capacity at constant pressure, J/K/mol ; Liquid
  • Temperature, K; Liquid
  • Molality, mol/kg - 1; Liquid
  • Pressure, kPa; Liquid
  • Liquid
  • Large sample (1 g) DSC
  • 180
  • POMD
  • 1
  • 3
  • Electrical conductivity, S/m ; Liquid
  • Molality, mol/kg - 1; Liquid
  • Pressure, kPa; Liquid
  • Temperature, K; Liquid
  • Liquid
  • Alternating current cell with electrodes
  • 18
  • POMD
  • 1
  • 3
  • Mass density, kg/m3 ; Liquid
  • Molality, mol/kg - 1; Liquid
  • Pressure, kPa; Liquid
  • Temperature, K; Liquid
  • Liquid
  • Vibrating tube method
  • 20
  • POMD
  • 2
  • 3
  • Molar heat capacity at constant pressure, J/K/mol ; Liquid
  • Temperature, K; Liquid
  • Molality, mol/kg - 2; Liquid
  • Pressure, kPa; Liquid
  • Liquid
  • Large sample (1 g) DSC
  • 148