Kinetics of oxygen dissolution in molten lead
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So l i d E l e c t r o l y t e
Electrode
Pb, O Indicator E l e c t r o d e
T h e c e l l h a s b e e n so d e s i g n e d t h a t t h e e l e c t r o d e c h a m b e r s a r e c o m p l e t e l y i s o l a t e d f r o m e a c h o t h e r . T h e o x y g e n i n l e a d i s f i r s t r e d u c e d t o a v e r y l o w v a l u e by b u b b l i n g h y d r o g e n . Subsequently, o x y g e n dissolution is a c h i e v e d t h r o u g h g a s diffusion a c r o s s t h e f r e e s u r f a c e o r through b u b b l e m e t a l i n t e r a c t i o n . D u r i n g all t h e s e r e a c t i o n s t h e electromotive f o r c e o f t h e cell c h a n g e s c o n t i n u o u s l y a n d is a u t o m a t i c a l l y r e c o r d e d . T h e diffusion c o e f f i c i e n t o f o x y g e n i n l e a d , a s c a l c u l a t e d f r o m t h e e x p e r i m e n t a l d a t a , i s 1.29 x 10-5 s q c m p e r s e c a n d t h e l i q u i d p h a s e m a s s t r a n s f e r c o e f f i c i e n t i s e s t i m a t e d t o be 0 . 0 3 5 c m p e r s e c a t 7 5 0 ° C . C O T U D I E S o n t h e d i s s o l u t i o n o f o x y g e n in l i q u i d m e t a l s a n d t h e r e m o v a l o f t h e gas a r e o f d i r e c t i m p o r t a n c e in t h e p r o p e r u n d e r s t a n d i n g of t h e r o l e of o x y g e n d u r i n g v a r i o u s m e t a l refining operations. The p r e s e n t i n v e s t i g a t i o n a i m s at s t u d y i n g s i m i l a r p h e n o m e n a in p u r e lead u s i n g a s o l i d electrolyte c e l l . T h e o x y g e n COntent Of t h e m o l t e n m e t a l m a y be r e d u c e d t o a l o w v a l u e by b u b b l i n g h y d r o g e n . S u b s e q u e n t l y , t h e m e t a l m a y be a l l o w e d t o d i s s o l v e o x y g e n f r o m a n o x i d i z i n g g a s e i t h e r by e x p o s i n g t h e f r e e s u r f a c e of t h e m e t a l t o t h e g a s o r by b u b b l i n g t h e g a s t h r o u g h the m o l t e n m e t a l . W h i l e t h e f i r s t t e c h n i q u e a l l o w s o n e to e s t i m a t e t h e diffusion c o e f f i c i e n t o f o x y g e n in t h e m o l t e n m e t a l , t h e s e c o n d y i e l d s v a l u a b l e information on the b u b b l e - m e t a l interaction. The available information o n t h e s e s u b j e c t s i s b r i e f l y reviewed below. MEASUREMENT
OF DIFFUSION
COEFFICIENT
A c c u r a t e m e a s u r e m e n t of the d i f f u s i o n c o e f f i c i e n t o f o x y g e n in d i f f e r e n t m e t a l l i c m e l t s a n d s o l i d m e t a l s h a s b e e n m a d e p o s s i b l e by t h e u s e o f s o l i d g a l v a n i c c e l l s . T h e v a r i o u s t e c h n i q u e s u s e d m a y be c a t e g o r ized u n d e r t h e following two distinct s u b h e a d s : 1) T h e c o u l o m e t r i c t i t r a t i o n m e t h o d , 1-3 i n w h i c h t h e d i f f u s i o n f l u x i s d e t e r m i n e d by m e a s u r i n g a s t e a d y o r unsteady c u r r e n t flowing through t h e c e l l , and 2) the o p e n c i r c u i t e l e c t r o m o t i v e f
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