Activities of oxygen in liquid copper and silver from electrochemical measurements
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16140 + 6.52 T(K) (_+ 380) J 9 g-atom -j
where the reference state for dissolved oxygen was an infinitely dilute solution. The present value of the partial entropy of oxygen dissolved in liquid copper differs significantly from that suggested by many investigators. Further, the present equation for liquid copper has been found to be consistent with a correlation proposed previously by the present authors. The equation for liquid silver is in good agreement with the published ones.
THE technological importance of the thermodynamic behavior of oxygen in liquid copper has led to a large number of experiments and some reviews on it. Especially, the dilute solutions of oxygen in liquid copper have received a great deal of attention in the literature because of their theoretical importance. However, there is some disagreement in the standard Gibbs energy of solution of oxygen in liquid copper determined by various investigators. 6-~7,2~ A comparison of the published values shows that the partial entropy of solution of oxygen in liquid copper reported by the German investigators differs significantly from those by the groups of other countries. For instance, according to Fischer and Ackermann 6 and Osterwald et al, 7,8 the value of the partial molar entropy of oxygen dissolved in liquid copper lies between + 0.5 and - 0.1 cal/gatom 9deg. On the other hand, most other investigators have reported the values of partial molar entropy between - 1 and - 5 cal/g-atom.deg. 9-17 Recently, the present authors have measured the activity coefficients of oxygen in several liquid elements of group IIIb to VIb. t-4 By combining our results with the published values for group VIII, a significant correlation of thermodynamic values between the various groups was proposed. In particular, plots of the partial entropy vs enthalpy of oxygen dissolved in a particular group of liquid elements are shifted gradually toward higher values of entropy as the group of the SHINYA OTSUKA is Research Associate, and ZENSAKU KOZUKA is Professor, Department of Metallurgical Engineering, Faculty of Engineering, Osaka University, Osaka, Japan. Manuscript submitted May 1, 1980. METALLURGICAL TRANSACTIONS B
element is changed from VIb to VIII. 2 For liquid copper, the data reported by the German investigators were found to be consistent with this correlation. However, most of the other data for liquid copper and all the available data for liquid silver differ significantly from those predicted by this correlation. Thus, more precise data for liquid copper and silver are required in order to clarify the thermodynamic behavior of oxygen dissolved in liquid elements of group lb. In the present investigation, the activity coefficients of oxygen in liquid copper and silver have been determined precisely by a modified coulometric titration method described previously. 1,3On the basis of the present experimental results, the thermodynamic behavior of oxygen dissolved in liquid elements of group Ib will be discussed and compared with that for other groups. E X P
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