Oxygen interactions in certain liquid Cu-M-O systems by a solid electrolytic cell technique
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and In 7o v s N M , r e s p e c t i v e l y . T h e i n t e r a c t i o n c o e f f i c i e n t s e M - 8--logfo/~% M and eM -- 8 l n T o / a N M , w e r e c a l c u l a t e d f r o m the s l o p e s of t h e s e two f i g u r e s at s m a l l c o n c e n t r a t i o n s of the a l l o y i n g e l e m e n t . T a b l e I sh o w s the v a l u e s obtained d i r e c t l y f r o m the
M. M. A. E L - N A G G A R AND N. A. D. P A R L E E
KS 160
T H I S p a p e r d e m o n s t r a t e s the f l e x i b i l i t y and a p p l i c a b i l i t y of a r e c e n t l y d e v e l o p e d t e c h n i q u e 1 for t h e r m o d y n a m i c m e a s u r e m e n t s on o x y g e n - l i q u i d m e t a l s y s t e m s . The a p p a r a t u s and p r o c e d u r e have b e e n d e s c r i b e d in an e a r l i e r p u b l i c a t i o n . I This t e c h n i q u e has b e e n s u c c e s s f u l l y u s e d in the p r e s e n t c a s e to e v a l u a t e the e f f e c t of the a l l o y i n g e l e m e n t s Au , P t , A g , and Ni on the s o l u b i l i t y and a c t i v i t y of oxygen in liquid c o p p e r s o l u t i o n s . The a l l o y w a s f o r m e d in e a c h c a s e by m i x i n g , at r o o m t e m p e r a t u r e , known w e i g h t s of c o p p e r and of the a l l o y i n g e l e m e n t in the c r u c i b l e . The c o m p o s i t i o n of the a l l o y w a s c a l c u Luted f r o m t h e s e w e i g h t s . Mixing took p l a c e t h r o u g h i n t e r d i f f u s i o n d u r i n g the long p e r i o d of g r a d u a l h e a t i n g and during the t h e r m a l e q u i l i b r a t i o n at the f i n al t e m p e r a t u r e f o r wh i ch m o r e than 6 hr w a s a l l o w e d . A l l the r u n s w e r e m a d e at t e m p e r a t u r e s c l o s e to 1200~ and e a c h u n d e r a c o n s t a n t oxygen p a r t i a l p r e s s u r e PO 9 The PO2 v a l u e s e m p l o y e d r a n g e d f r o m 6.2 x 10 -7 5o 1.59 • 10 -~ a t m , and depended upon what a p p e a r e d m o s t s u i t a b l e for e a c h s y s t e m and to avoid the f o r m a t i o n of any oxide p h a s e ; h o w e v e r , the P02 u s e d with s o m e of the h i g h e r n i c k e l a l l o y s w a s p r o b a b l y s u f f i c i e n t to p r e c i p i t a t e NiO but no s e c o n d p h a s e could be d e t e c t e d . A l loying e l e m e n t c o n c e n t r a t i o n s of up to 20 wt p ct w e r e u s e d . It was o b s e r v e d that a l l of t h e s e a l l o y i n g e l e m e n t s r e d u c e the o x y g e n s o l u b i l i t y at c o n s t a n t PO2 in liquid c o p p e r . B e c a u s e it w a s not e a s y to r e p r o d u c e e x a c t l y the s a m e PO2 v a l u e in a l l the r u n s the e f f e c t of the a l loying e l e m e n t c o n c e n t r a t i o n on the s o l u b i l i t y of oxygen is p r e s e n t e d in t h e f o r m of t h e i r e f f e c t on t h e v a l u e of K s , w h e r e K s is defined as Q%/d-P-o 2. Such an e f f e c t is i l l u s t r a t e d in F i g . 1, a l s o in F i g s . 2, 3, and 4, w h i l e F i g . 5 shows the e
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