Activities of oxygen in liquid thallium and indium from electrochemical measurements
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-22000 + O. 74 T (±300) cal/g-atom
--92000 + 3.10 T (+1300) J/~-atom, AG°(in In) = --42450 + 3.30 T (+350) c a l / g - a t o m = -177600 + 13.8 T (±1500) J / g - a t o m , =
where the reference s t a t e for dissolved oxygen was an infinitely dilute solution. It was reconfirmed that the apparent initial oxygen concentration observed in the r a n g e of very low oxygen concentration in liquid m e t a l was attributed to the oxygen released from the solid electrolyte. IN a previous paper,x the present authors proposed a modified coulometric titration method to determine the oxygen activity in liquid metal. The fairly low oxygen concentration in liquid lead and antimony could be precisely determined by this method, because any errors due to the electronic conduction in a solid e l e c t r o l y t e and the r e l e a s e of oxygen from the electrolyte were avoided. One of the purposes of this paper is to apply this method to the measurements of the oxygen activities in liquid thallium and liquid indium. Reliable data have not been reported yet on the oxygen activity in liquid thallium. Also, results on the oxygen activity in liquid indium are significantly inconsistent among authors, z'4 P r e s e n t experimental results will be t h e r e fore useful for clarification of the thermodynamic behavior of oxygen dissolved in liquid IIIb elements of periodic table. Another p u r p o s e of this paper is to reconfirm that the apparent initial oxygen concentrations observed in the r a n g e of very low true oxygen concentration in liquid m e t a l are attributed to the oxygen released from a solid electrolyte. Such apparent values observed for liquid thallium and indium were therefore compared with those for other liquid metals.
liquid m e t a l would be calculated according toI
Mm
PRINCIPLE
In the present investigation, the same potentiostatic pump-out experiments as in the previous paper1 are performed by using an electrochemical cell of the cyli n d e r type: O in liquid metal/ZrO2(+CaO)/Air, P t , and the electrical c h a r g e contributed by ionic current passing through the cell is analyzed. The experimental principles were already presented in a previous paper ~ and only a b r i e f description is given h e r e . If Henry's law can be applied to the oxygen in liquid metal, an apparent initial oxygen concentration in the SHINYA OTSUKA and ZENSAKU KOZUKA are Research Associateand Professor, respectively, Department of Metallurgical Engineering, Faculty of Engineering, Osaka University, Osaka, Japan. TOYOKAZU SANO is GraduateStudent,Graduate Schoo], Osaka University, Osaka, Japan. Manuscript submitted September4, 1979. METALLURGICAL TRANSACTIONS B
x
{
'-2AEF,~ -1
1 - e x p ~ ]I
[1] where C~(app.) is the apparent initial oxygen concentration in the liquid m e t a l in atomic percent (at. pct), Qion (coulomb) the total quantity of electrical c h a r g e due to ionic current, AE the difference between the initial and final emf, and Mrn and Wm the atomic weight and weight of liquid m e t a l , respectively. In the c
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