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Determination of Aluminum Content of Bayer Liquors by Electrical Conductivity Measurement G. R. B R O W N E A N D C. W. P. F I N N A s p a r t o f a n i n v e s t i g a t i o n into e f f e c t s o f o r g a n i c contaminants on alumina precipitation from s o d i u m a l u m i n a t e l i q u o r s , a m e t h o d w a s r e q u i r e d f o r the d e termination of aluminum c o n t e n t over extended p e r i o d s up t o 36 h . S t a n d a r d c h e m i c a l m e t h o d s w e r e f o u n d t o be t e d i o u s 1 t i m e c o n s u m i n g a n d s l o w . I n v e s t i g a t i o n s o f literature s u g g e s t e d a possible correlation between s o l u t i o n e l e c t r i c a l c o n d u c t i v i t y a n d f r e e s o d a (NazO) c o n t e n t , w h i c h i s d i r e c t l y r e l a t e d t o the a l u m i n u m c o n t e n t a t c o n s t a n t t o t a l c a u s t i c c o n t e n t .2 T h i s w a s i n v e s t i g a t e d a t l o w f r e e s o d a c o n t e n t by H e y r o v s k y 3 a n d by Glastonbury 4 at higher c o n c e n t r a t i o n s at 25°C. In o r d e r t o m o r e c l o s e l y a p p r o x i m a t e B a y e r P l a n t c o n d i t i o n s , p r e c i p i t a t i o n r u n s w e r e d o n e a t 6 9 ° C . s No p u b l i s h e d d a t a c o u l d be f o u n d of the e l e c t r i c a l c o n d u c t i v i t y of s o d i u m a l u m i n a t e s o l u t i o n s i n t h i s t e m p e r a t u r e r a n g e . T h e c o n d u c t i v i t y o f the s o d i u m a l u m i n a t e s o l u t i o n s was m e a s u r e d u s i n g a P h i l l i p s C o n d u c t i v i t y M e t e r PW95501/01 w i t h a 200 H z i n p u t a n d a P R 9 5 1 4 / 1 0 i m m e r s i o n c o n d u c t i v i t y p r o b e w i t h a c e l l c o n s t a n t of 1.0 c m -1. A 1.00 ± 0.01 o h m r e s i s t o r w a s u s e d a s a n external standard without temperature compensation. V a r i a t i o n s i n c o n d u c t i v i t y w e r e d e t e r m i n e d a t 69.0 ± 0 . 5 ° C f o r m e c h a n i c a l l y s t i r r e d s o l u t i o n s o f 93 g 1-1 NazO a n d A1203 i n t h e r a n g e 0 t o 94.5 g 1-1 i n 1 l i t e r stainless s t e e l b e a k e r s . T h o s e solutions were obtained by t h e d i s s o l u t i o n o f k n o w n w e i g h t s o f e l e c t r i c a l g r a d e aluminum in p u r e , c a r b o n a t e f r e e , s o d i u m h y d r o x i d e solutions and checked b e f o r e and after m e a s u r e m e n t s by t i t r a t i o n . 6 T h e m e a s u r e d c o n d u c t i v i t i e s A of t h e s o l u t i o n s a r e

G. R. BROWNE, formally Post-Graduate Student, School of Mining and Mineral Technology, Kalgoorlie, Western Australia is presently Metallurgist, Kambalda Nickel Operations, Western MiningCorporation. C. W. P . FINN is Alcoa Foundation Lecturer in Thermodynamics, School of Mining and Mineral Technology, Kalgoorlie, Western Australia, 6 4 3 0 . Manuscript submitted November 16, 1976. METALLURGICAL

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