Studies of the sodium oxide-sodium sulfate system

Abstract

6) The small term (0.04 f 0.16) (DN/kJ mot') has been neglected inside the square brackets. Similarly negligible dependencies on the donor properties of the solvents were obtalned also for azide, tetraphenyiborate, and thiocyanate anlons, besides chloride. Only for bromide and i d i e are the coefficients of (DN/W mol-') comparable with the standard error: 0.13 * 0.17 and -0.17 f 0.08, respectively.(The original definitions of E, and DN are in terms of kcai mol-'; 1 cal = 4.184 J.) (7) A. Publication costs assisted by the Naval Research LaboratoryThe behavior of Na20-Na2S04 melts at 920 "C has been studied by four techniques; (1) chemical analysis of quenched melts, (2) manometric experiments in which the reversible uptake of O2 by the melts was observed,(3) potentiometric studies, using oxide ion specific zirconia electrodes, and (4) voltammetry, which detects the number of oxidizable species. In oxygen atmospheres all four studies are consistent with peroxide formation in the melt, although values of the peroxide/oxide ratio vary somewhat with method. At low O2 pressures (<0.1%), the potentiometric results are anomalous. 02,16Two prominent anodic waves were observed when Na20 was added to the melt; the first (wave I) occurred at --LO6 V vs. the Ag/Ag2S04 reference electrode and the second (wave 11) at --0.07 V. A third anodic wave appeared as a shoulder of anodic wave I1 at --0.49 V.This shoulder disappeared when the oxygen pressure above the melt was increased, as shown in Figure 7. Even though the shoulder was not positively identified, it is probably due to some oxidizable impurity in Na20.for curves A, B, and C, respectively. 02-+ 202 = 202-

Thermodynamic evaluation and optimization of the (Na2SO4+ K2SO4+ Na2S2O7+ K2S2O7) system

“…The liquid model considers two cations, Na + and K + , and two anions, SO 2À 4 and S 2 O 2À 7 . In reality, the liquid might also contain the anions S 3 O 2À 10 [6,18], O 2À and O 2À 2 [31][32][33], or dissolved molecular SO 3 [7], but it is expected that these species occur in very low concentrations in the (Na,K) 2 (SO 4 ,S 2 O 7 ) system, and therefore do not affect the chemical equilibrium to any great extent. The Gibbs free energy of the quadruplets is defined as follows: For the unary quadruplet containing two cations A and two anions X, the Gibbs free energy is defined as [30]:…”

Oxide Ion Titrations in Molten NaCl with the Zirconia Electrode

“…If the electrode behaves reversibly, as indicated by reaction [4], and if the temperature is sufficiently high for the conductivity of the ceramic to be appreciable, it should be possible to titrate O 2-ions into and out of melts by the application of an applied potential between the O21 (Pt) electrode attached to one side of the zirconia and a suitable counterelectrode. The resulting change in the O 2activity of the melt is measured by a cell /vhich has been described in detail elsewhere (5,11). NaC1 was used as the molten salt medium since the chemistry of oxides dissolved in it had been studied previously (5).…”