Determination of the standard gibbs energy for the reaction of 3BaO (s) + 2Cr (s) + 3/2O2 (g) = 3Ba0 · Cr2O3 (s)

The standard Gibbs energy of formation of 3BaO · Cr₂O₃ has been measured by a chemical equilibrium technique and is expressed as follows: 3BaO (s) + 2Cr (s) + 3/2 O₂ (g) = 3BaO · Cr₂O₃ (s) ΔG^o = -1,260,000 (±3000) + 282 (±24)r(J/mol) The activity coefficient of chromium in copper, which was needed for the foregoing measurement, may be expressed by the following equation: 5790 log γ _Cr ^{o =5790/T-2.10} The value of standard Gibbs energy at 1573 K was found to be close to that of reaction of formation of CaO · Cr₂O₃ expressed in the similar form. The BaO saturated BaF₂ flux is shown to be far more promising in the oxidative dephosphorization of chromium-containing hot metal in comparison with the CaO-SiO₂-CaF₂ flux doubly saturated with CaO and 3CaO-Cr₂O₃.     

Chemical potentials of oxygen for mixtures of CaO (s) + Ca4P2O9 (s) + {CaO + P2O5 + FexO} melts and Ca4P2O9 (s) + Ca3P2O8 (s) + {CaO + P2O5 + FexO} melts

Electrochemical measurements involving stabilized zirconia as solid electrode and Mo + MoO₂ as reference electrode were conducted in order to determine the chemical potentials of oxygen for threephase assemblages of CaO (s) + Ca₄P₂O₉ (s) + liquid and Ca₄P₂O₉ + Ca₃P₂O₈ + liquid within the system CaO + Fe_xO + P₂O₅. The results for the former are $$\log (P_{O_2 } /atm) = 6.22 - 27,900 (T/K)$$ while for the latter, $$\log (P_{O_2 } /atm) = 6.35 - 27,600 (T/K)$$      

三元配合物[RE(Gly)4(Im)(H2O)](ClO4)3(RE=La,Pr)的热化学研究

利用自行研制的新型恒温环境反应量热计,以2mol·L-1HCl做溶剂,分别测定了LaCl3·7H2O、PrCl3·6H2O、[La(Gly)4(Im)(H2O)](ClO4)3、[Pr(Gly)4(Im)(H2O)](ClO4)3、Im、NaClO4、Gly、NaCl在298.15K时的溶解焓,再通过设计的热化学循环求得化学反应的摩尔反应焓,利用这些结果和其它辅助数据,计算出两种配合物的标准摩尔生成焓分别为:ΔfH m{[Prm{[La(Gly)4(Im)(H2O)](ClO4)3,s}=-3459.3±0.2kJ·mol-1;ΔfH (Gly)4(Im)(H2O)](ClO4)3,s}=-3460.63±0.18kJ·mol-1。     

Chemical potentials of oxygen for three-phase assemblages of CaSiO3(s) + Ca3Si2O7(s) + {CaO + SiO2 + FexO} melt and Ca3Si2O7(s) + Ca2SiO4(s) + {CaO + SiO2 + FexO} melt

By employing an electrochemical technique involving stabilized zirconia as solid electrolyte and Mo + MoO₂ mixture as reference electrode, the equilibrium oxygen partial pressures for three-phase assemblages of CaSiO₃(s) + Ca₃Si₂O₇(s) + {CaO + SiO₂ + Fe_xO} melt and Ca₃Si₂O₇(s) + Ca₂SiO₄(s) + {CaO + SiO₂ + Fe_xO} melt were determined as: - log {P_O2 (CS + C₃S₂ + L)/bar} = - 3.22 13000/(T/K) ± 0.05 - log {P_O2 (C₃S₂ + C₂S + L)/bar} = - 0.92 16400/ (T/K) ± 0.04. respectively, where CS, C₃S₂ and C₂S indicate CaSiO₃(s), Ca₃Si₂O₇(s). and Ca₂SiO₄(s), respectively.     

Acid dissolution of willemite (Zn,Mn)2 SiO4) and hemimorphite (Zn4Si2O7(OH)2 H2O)

The influence of temperature, pH, acid type, and surface area on the kinetics of the acid dissolution of natural and synthetic willemites and natural hemimorphites has been investigated. Specific rate constants, based upon areas determined by krypton adsorption measurements, were estimated from the experimental data obtained. For both willemite and hemimorphite, the rates of dissolution in different acids are shown to be related to the relative strengths of zinc-acid anion complexes. The reactivity of willemite toward acids increases with increasing replacement of zinc by manganese. Mixed chemical/diffusion control is responsible for the observed rates of willemite dissolution under the conditions studied (HNO₃, HCl, HClO₄, H₃PO₄, H₂SO₄, pH 0.31 to 3.00,T 21 to 94 °C). Estimates of the relative contributions of chemical and diffusional resistances to the overall rate have been made for the dissolution of manganese-free willemite in sulfuric acid solutions. The experimentally measured rates have been demonstrated to be in reasonable agreement with predicted overall dissolution rates. Proposals are made regarding the nature of the diffusion and chemical steps involved in the dissolution process. Hemimorphite was found to be considerably more reactive than willemite and its dissolution is primarily diffusion controlled under the conditions studied (T 20 to 76 °C, pH 2 to 3.5). Formerly a Postgraduate Research Student, Department of Metallurgy and Materials Science, Royal School of Mines, Imperial College, London