The free energy of solution of oxygen in liquid copper by a solid electrolytic cell technique
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The Free Energy of Solution of Oxygen in Liquid Copper by a Solid Electrolytic Cell Technique
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c e n t r a t i o n of a d s o r b e d c a r b o n o b v i o u s l y i s p r o p o r ' t i o n a l t o t h e a c t i v i t y of c a r b o n .
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During the carburization and the decarburization t h e r e a c t i o n s t e p (VII) i s a l w a y s i n e q u i l i b r i u m a n d from the kinetics it can be seen that the surface concentration in equilibrium with dissolved carbon is p r o p o r t i o n a l to t h e t h e r m o d y n a m i c a c t i v i t y of c a r b o n in the system. The experimentally determined kinetics further show that the coverage with adsorbed carbon is low and far from being complete, since t h e r e i s n o r e t a r d a t i o n o f t h e f o r w a r d r e a c t i o n a n d of the backward reaction at high carbon activities. This result is in agreement with measurements of K o z a k e v i t c h a n d U r b a i n , 5 who d e m o n s t r a t e d t h a t c a r b o n h a s v i r t u a l l y n o e f f e c t on t h e s u r f a c e t e n s i o n o f l i q u i d i r o n . T h u s c a r b o n i s n o t s u r f a c e a c t i v e in l i q u i d a n d p r e sumably not in solid iron. Several models have been proposed to explain the d e v i a t i o n f r o m p r o p o r t i o n a l i t y of a c t i v i t y a n d s o l v a t e c o n c e n t r a t i o n i n t h e s o l i d s o l u t i o n s o f c a r b o n in a u s t e n i t e . 4 , 6-lo O f t e n r e p u l s i v e i n t e r a c t i o n s b e t w e e n c a r bon atoms have been assumed for an interpretation. Now repulsion obviously only occurs in the solid solution and not at the surface, since the surface concentration changes proportionally with the activity. T h i s n e w k n o w l e d g e i s in a g r e e m e n t w i t h a m o d e l , which recently has been supported by Monte Carlo c o m p u t a t i o n s . 1~ It i s a s s u m e d t h a t a d i s s o l v e d c a r bon atom pushes outward its six iron atom neighbors. These solvent atoms thereby block the six neighbor i n t e r s t i t i a l s i t e s on t h e o p p o s i t e s i d e . T h i s s o r t of interaction does not occur between carbon atoms at the surface, therefore the surface concentration can b e p r o p o r t i o n a l to t h e c a r b o n a c t i v i t y . METALLURGICAL TRANSACTIONS
M. M. A. E L - N A G G A R
AND N. A. D. P A R L E E
T H I S p a p e r d e s c r i b e s t h e r e s u l t s of a n o v e l m e t h o d of d e t e r m i n i n g t h e s t a n d a r d f r e e e n e r g y of s o l u t i o n of o x y g e n i n l i q u i d m e t a l s l i k e c o p p e r , w h i c h g r e w o u t of earlier exploratory work I using a somewhat different technique. An e s s e n t i a l p a r t of t h e a p p a r a t u s i s t h e r e a c t i o n t u b e - e l e c t r o l y t i c c e l l c o m b i n a t i o n
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