-TECHNICAL PAPERS SOLID-STATE SCIENCE AND TECHNOLOGY Activity of Oxygen in Liquid Sn and BaxCUl_x Alloys

The activity of oxygen in liquid Sn f rom 800 to 900°C and in liquid Ba~Cu,_x (x = 0.25 and 0.35) at 900°C have been measured by a modified coulometric titration method on the galvanic cell: O in liquid Sn or Ba=Cu~_Jyttr ia stabilized zireonia/Air, Pt. The standard Gibbs energy changes for the reaction 1/2 O2 (I arm)- ~ O (i a tom percent) in liquid Sn metal are determined tobe AG ° =-177,940 + 22 T (K) (_+300) J/g-atom. AG ° for Ba~Cu~_ ~ liquid alloys at 900°C are-244,920 and-259,464 J/g-atom, respectively, for x = 0.25 and 0.35. The activity coefficients of the Ba=Cul_ = alloys are noted to deviate from the quasi-interstitial and quasi-substitutional solvation-shell models. A modified coulometric titration method has been ap-plied successfully to measure the activity and diffusion coefficients of oxygen dissolved in various liquid metals and alloys) The activity coefficients of oxygen dissolved in liquid metals have been extensively measured for elements from group VIIIA to VIB but not for IIA group and the rare earth metals because the latter are very reactive and may attack the electrolyte causing a change in the electrolyte and the contamination f the melts. However, by alloyin