The equilibrium solubility of nitrogen in aluminosilicate melts
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T h e equilibrium solubility of nitrogen in aluminosilicate melts, similar in composition to m a n y blast furnace slags, has been m e a s u r e d , although the silica contents u n d e r investigation have been limited by experimental p r o b l e m s to b e t w e e n 30 and 38 mole pct. T h e solubility is a c h e m i c a l rather than a physical p h e n o m e n o n , it b e i n g n e c e s s a r y to i m p o s e s e v e r e reducing conditions to obtain significant quantities of nitrogen in solution. T h e dependence of solubility on slag basicity has been investigated, and a s i m p l e dependence upon nitrogen and c a r b o n m o n o x i d e contents in the gas p h a s e established. F r o m the results, it is postulated that an e x c h a n g e reaction t a k e s place b e t w e e n nitrogen gas and bridging o x y g e n a t o m s in the aluminosilicate structure, and the results are discussed in relation to the structure of the melts.
THE w o r k
d e s c r i b e d in t h i s p a p e r was c a r r i e d out in c o n n e c t i o n w i t h a s t u d y into t h e c a u s e s o f p o r o s i t y i n pit-cooled b l a s t furnace s l a g . S e v e r a l r e a s o n s have been advanced for t h e development of such p o r o s i t y , but d u r i n g a n i n v e s t i g a t i o n into t h e n a t u r e o f the g a s e v o l v e d f r o m c o o l i n g s l a g , n i t r o g e n w a s f o u n d t o be p r e s e n t in c o n s i d e r a b l e q u a n t i t i e s . ~ T h i s l e d to t h e belief t h a t n i t r o g e n d i s s o l v e s in t h e s l a g d u r i n g b l a s t f u r n a c e o p e r a t i o n , t o be e v o l v e d o n c o o l i n g i n t h e f o r m of p o r o s i t y . It w a s t h u s d e c i d e d t o s t u d y i n t h e l a b o r a t o r y t h e c o n d i t i o n s u n d e r w h i c h n i t r o g e n c a n be diss o l v e d in t h e s l a g . P r e v i o u s w o r k o n t h e s o l u t i o n o f n i t r o g e n in s i l i c a t e m e l t s s h o w e d t h i s t o be a c h e m i c a l r a t h e r t h a n a p h y s ical p h e n o m e n o n . Lindeskog, e equilibrating b l a s t furnace slag with nitrogen o n a laboratory s c a l e , found s o l u b i l i t i e s o f a b o u t 0.01 wt p c t , w h i c h r o s e t o 0 . 0 5 wt p c t w h e n c a r b o n was a d d e d . Mulfinger a n d his c o w o r k e r s 3-~ f o u n d that t h e p h y s i c a l s o l u b i l i t y o f n i t r o g e n i n g l a s s w a s v e r y l o w but that t h e a d d i t i o n of h y d r o g e n o r c a r b o n l e d to c h e m i c a l e f f e c t s w h i c h considerably e n h a n c e d the s o l u b i l i t y ; a d d i t i o n of c a r b o n m o n o x i d e , on the o t h e r h a n d , d e c r e a s e d t h e s o l u b i l i t y . K a m y s h o v , Esin, and C h u c h m a r e v 6' 7 u s i n g synthetic slags similar
in composition to blast furnace slags, carried out exp e r i m e n t s in w h i c h N 2 - C O m i x t u r e s w e r e bubbled through the m e l t s contained in c a r b o n crucibles. E q u i librium quantities of nitrog
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