Thermodynamics Research Center / ThermoML | Thermochimica Acta

Vapour pressure and standard enthalpy of sublimation of alkali-metal fluoroborates

Pankajavalli, R., Jain, A.[Ashish], Anthonysamy, S., Ananthasivan, K., Vasudeva Rao, P. R.
Thermochim. Acta 2007, 452, 1, 1-6
ABSTRACT
The temperature dependence of the vapour pressures of solid alkali-metal fluoroboratesMBF4 (M = Na, Rb or Cs) were experimentally determined using an improvised transpiration technique. The vapour pressure of NaBF4 could be represented by the following least-squares expressions: log(p/Pa) [NaBF4, orthorhombic] = 7.06(+-0.03) - 3734(+-360) (K)/T log(p/Pa) [NaBF4, monoclinic] = 6.03(+-0.04) - 3192(+-80) (K)/T The enthalpy pertaining to the transition from the orthorhombic to the monoclinic phase at 527 K, was found to be 10.4 kJ mol-1. The measured vapour pressures of RbBF4 and CsBF4 could be represented by the following least-squares expressions: log(p/Pa) [RbBF4] = 6.21(+-0.04) - 4020(+-87) (K)/T log(p/Pa)[CsBF4] = 7.77(+-0.04) - 5209(+-108) (K)/T By using the third law analyses of the data, H.sub of MBF4 (M = Na, Rb or Cs) at 298K were determined to be 89.4+-1.5, 123.4+-1.9 and 135.7+-0.8 kJ mol-1, respectively.
Compounds
# Formula Name
1 BF4Na sodium tetrafluoroborate
2 BF4Rb rubidium tetrafluoroborate
3 BCsF4 cesium tetrafluoroborate
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
  • 1
  • Triple point temperature, K ; Crystal 2
  • Crystal 2
  • Crystal 1
  • Air at 1 atmosphere
  • DTA
  • 1
  • POMD
  • 1
  • Vapor or sublimation pressure, kPa ; Crystal 2
  • Temperature, K; Crystal 2
  • Crystal 2
  • Gas
  • Transpiration method
  • 6
  • POMD
  • 1
  • Vapor or sublimation pressure, kPa ; Crystal 1
  • Temperature, K; Crystal 1
  • Crystal 1
  • Gas
  • Transpiration method
  • 19
  • POMD
  • 2
  • Triple point temperature, K ; Crystal 2
  • Crystal 2
  • Crystal 1
  • Air at 1 atmosphere
  • DTA
  • 1
  • POMD
  • 2
  • Vapor or sublimation pressure, kPa ; Crystal 1
  • Temperature, K; Crystal 1
  • Crystal 1
  • Gas
  • Transpiration method
  • 16
  • POMD
  • 3
  • Triple point temperature, K ; Crystal 2
  • Crystal 2
  • Crystal 1
  • Air at 1 atmosphere
  • DTA
  • 1
  • POMD
  • 3
  • Vapor or sublimation pressure, kPa ; Crystal 1
  • Temperature, K; Crystal 1
  • Crystal 1
  • Gas
  • Transpiration method
  • 18