D. R. Gaskell

The densities and structures of melts in the system CaO-“FeO”-SiO2

The densities of melts in the systems CaO-SiO2, CaO-“FeO,” “FeO”-SiO2 and in ternary melts containing 33 and 44 mole pct SiO2 have been measured from the liquidus temperature to 1600°C. Structural interpretation of melt density and expansivity has provided information on the nature of the ions present in these systems, and, in conjunction with known thermodynamic behavior, has indicated the natures of the interactions occurring among these ions. The influence of temperature, silica content andCaO/FeO ratio on the structures of ternary iron-calcium silicates is discussed.

Activities and free energies of mixing in binary silicate melts

The thermodynamic properties of the Whiteway, Smith and Masson (WSM) models of polymerized silicate melts are calculated. The free energy is calculated as a function of composition and degree of polymerization of the silicate ions from heats of mixing and Guggenheim’s expression for the configurational entropy of a system of linear and branched chain polymer molecules in which random mixing of the mer units occurs. The variations, with composition, of the equilibrium degree of polymerization, the activities of solution components and the free energy of mixing are calculated as functions of the stability of the solid orthosilicate compound. Under the assumption of random mixing of the mer units, the thermodynamic properties are found to be independent of whether the SiOin4su4 ion is considered to be a bifunctional or tetrafunctional polymerizing unit. It is found that the apparent differences between the dependencies, on composition, of the ion fraction of O2- in the WSM linear chain model and the WSM branching chain model are the result of the assumption, in these models, that random mixing of the anions occurs,i.e. that the systems exhibit Temkin behavior. It is suggested that the deviations of the theoretical free energies of mixing from experimental measurement, which begin when the mole fraction of silica is between 0.3 and 0.4, are due to the first significant appearance of ring ions in actual silicate melts at some composition within this range.

The thermodynamic properties of melts in the system MnO-SiO2

The activity of MnO in MnO-SiO2 melts has been measured at 1400, 1500 and 1600 °C by means of the technique in which equilibrium is established between the melt, a gaseous atmosphere of fixed oxygen pressure and a Pt-Mn foil immersed in the melt. The variation of the activity of SiO2 with composition and temperature and the integral free energies, and partial heats and entropies are derived. The activity of MnO and the free energy of formation of liquid Mn2SiO4 are well represented by Whiteway, Smith and Masson’s polymerization model of liquid silicates with Ink1,1 = −5212/T + 1.011. Correlation of the results of the present study with previous measurements indicates that solubility of SiO2 in MnO-SiO2 melts is a significant function of oxygen pressure.

The self diffusion of iron in Fe2SiO4 and CaFeSiO4 melts

AbstractThe self diffusion of iron in Fe2SiO4 and CaFeSiO4 melts has been measured in the temperature range 1250° to 1540°C using Fe59 as the radio tracer and the capillary-liquid reservoir method of diffusion measurement. The results obtained are represented by

The Thermodynamic Properties of the Masson Polymerization Models of Liquid Silicates

log D_{Fe} = - \frac{{3800 \pm 500}}{T} - 2.74 \pm 0.29

Cryoscopic studies in fluoride-oxide-silica systems: Part I. systems containing Li+, Na+ and K+

for Fe2SiO4, and

Cryoscopic studies in fluoride-Oxide-Silica systems: Part II. systems containing Mg2+, Ca2+, Ba2+ and Pb2+

log D_{Fe} = - \frac{{5450 \pm 620}}{T} - 1.93 \pm 0.37