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addition of a n i m a l glue to the zinc e l e c t r o l y t e u s e d in zinc e l e c t r o w i n n i n g p l a n t s 1"4 s e r v e s s e v e r a l p u r p o s e s . The glue additions c o n t r o l cathode growth 1 to give smooth cathode zinc d e p o s i t s , i n h i b i t the d e l e t e r i o u s effects that i m p u r i t i e s such as a n t i m o n y have on the c u r r e n t efficiency of zinc e l e c t r o d e p o s i tion, 1 and d e c r e a s e acid m i s t evolution by f o r m i n g s t a b l e foam l a y e r s on the e l e c t r o l y t i c cell tops in conj u n c t i o n with a d d i t i v e s such as m - p - c r e s o l , s A l a r g e n u m b e r of solid and liquid a n i m a l glues a r e a v a i l a b l e c o m m e r c i a l l y , with v a r i a t i o n s in p h y s i c a l and c h e m i c a l p r o p e r t i e s due to d i f f e r e n t r a w m a t e r i a l s o u r c e s and methods of p r e p a r a t i o n . T h e s e a n i m a l glues a r e often e v a l u a t e d f o r u s e in zinc e l e c t r o w i n n i n g by t e s t i n g in s m a l l pilot e l e c t r o l y s i s c e l l s p r i o r to t h e i r u s e in the zinc t a n k r o o m s . T h i s technique has the d i s a d v a n t a g e of b e i n g both tedious and not p a r t i c u l a r l y s e n s i t i v e to v a r i a t i o n s i n additive p r o p e r t i e s a m o n g the v a r i o u s glues. A cyclic v o l t a m m e t r y t e c h n i q u e has b e e n developed 7 i n which the effects of v a r i o u s p a r a m e t e r s on the o v e r p o t e n t i a l s a s s o c i a t e d with z i n c e l e c t r o w i n n i n g can be r e a d i l y o b s e r v e d and m e a s u r e d . A n t i m o n y , an e l e c t r o l y t e i m p u r i t y which is h a r m f u l to the c u r r e n t effic i e n c y of zinc e l e c t r o w i n n i n g , was shown to d e c r e a s e the o v e r p o t e n t i a l s a s s o c i a t e d with zinc e l e c t r o d e p o s i tion. A n i m a l glue, a n o r g a n i c additive which m o d i f i e s the growth of the zinc d e p o s i t s and i n h i b i t s i m p u r i t y effects, i n c r e a s e d the o v e r p o t e n t i a l when added to the zinc e l e c t r o l y t e and t h e r e b y c o u n t e r a c t e d the effect that a n t i m o n y as an i m p u r i t y had on the o v e r p o t e n t i a l . T h e s e o p p o s i n g effects that i m p u r i t i e s and o r g a n i c a d d i t i v e s have on the zinc o v e r p o t e n t i a l w e r e u s e d to develop a cyclic v o l t a m m e t r i c method for r a p i d l y e v a l u a t i n g the e f f e c t i v e n e s s of v a r i o u s o r g a n i c a d d i t i v e s in c o u n t e r a c t i n g i m p u r i t y effects in zinc e l e c t r o winning. R. C. KERBY is Research Metallurgist and H. E. JACKSON is Senior Research Chemist at the Technical Research Centre, Cominco Ltd., Trail, B.C., Canada. T. J. O'KEEFE is Professor of Metallurgical Engineeringand Senior Investigator (Materials) and YAR-MINGWANG is Lecturer and Investigator (Materials) at GCMR, Universi