( nr\\ ADApDAPU I MOPEI, in rvLMr\\j\jr\Mr n Trademark Reg. U.S. Pat. Off.
MANUAL E. H . S a r g e n t & C o . , t h e m a n u f a c t u r e r of P o l a r o g r a p h s , offers three different P o l a r o g r a p h s — the Model X X I Visible Recording;
Chart
the Model X I I
Photographic Recording,
and
the Model I I I M a n u a l . T h e M o d e l III
Polarograph.
may b e used i n any p h a s e of p o l a r o g r a p h y , b u t it is p a r t i c ularly r e c o m m e n d e d for a p p l i c a t i o n s t o w h i c h it is p e c u l i a r l y suited a n d i n w h i c h r e c o r d i n g facilities are u n n e c e s s a r y . The M o d e l I I I is r e c o m m e n d e d : (1) I n t h o s e r o u t i n e analyses w h e r e o n l y o n e substance is d e t e r m i n e d and -where t h e step s h a p e a p p r o x i m a t e s a p u r e f o r m , c h a r a c t e r i s t i c o f r e v e r s i b l e r e a c t i o n s inv o l v i n g s i m p l e ions in fairly s u b s t a n t i a l c o n c e n t r a t i o n s . In s u c h cases, step h e i g h t may b e m e a s u r e d a s the difference b e t w e e n two p o i n t s , o n e on t h e r e s i d u a l c u r r e n t p l a t e a u a n d o n e o n t h e diffusion c u r r e n t p l a t e a u . For m e a s u r e m e n t s of t h i s t y p e , a s i m p l e m a n u a l i n s t r u m e n t such a s t h e M o d e l I I I is p r e f e r a b l e t o a r e c o r d i n g P o l a r o g r a p h b e c a u s e of t h e s p e e d a n d ease w i t h w h i c h it may be o p e r a t e d e v e n b y r e l a t i v e l y n o n - t e c h n i c a l p e r s o n n e l . (2) I n those l a b o r a t o r i e s w h e r e a r e c o r d i n g i n s t r u m e n t is now i n u s e f o r several d e t e r m i n a t i o n s , a M o d e l III may be u s e d f o r e a c h d e t e r m i n a t i o n , t h u s r e l e a s i n g t h e r e c o r d ing P o l a r o g r a p h for r e s e a r c h p u r p o s e s a n d f o r establishing t h e c o n d i t i o n s o f t h e r o u t i n e a n a l y s e s . (3) I n the p e r f o r m a n c e o f a m p e r o m e t r i c t i t r a t i o n s . (4) F o r i n s t r u c t i o n a l p u r p o s e s i n e d u c a t i o n a l i n s t i t u t i o n s w h e r e the 315 mm. l o n g , r e a d i l y v i s i b l e scale a n d t h e simplicity of d e s i g n m a k e t h e M o d e l I I I P o l a r o g r a p h ideal for d e m o n s t r a t i o n s a n d i l l u s t r a t i o n of the b a s i c c i r c u i t employed i n P o l a r o g r a p h s . Essentially the M o d e l I I I p r o v i d e s facilities f o r t h e incremental a p p l i c a t i o n of voltage across t h e d r o p p i n g mercury e l e c t r o d e c e l l a n d f o r i n d i c a t i n g t h e r e s u l t a n t current p a s s i n g t h r o u g h t h e cell. T h e cell c u r r e n t is measured by a h i g h l y sensitive g a l v a n o m e t e r from w h i c h a line l i g h t i m a g e is t r a n s m i t t e d , t h r o u g h a m i r r o r system, to a t r a n s l u c e n t scale l o c a t e d a b o v e t h e i n s t r u m e n t p a n e l . The scale is d o u b l e g r a d u a t e d f r o m — 1 5 0 to + 1 5 0 m m .
SARGENT
w i t h z e r o c e n t e r in r e d at t o p a n d f r o m z e r o to -}-300 m m . in b l a c k at t h e b o t t o m . T h e scale is 31.5 c m . l o n g , w i t h c i r c u l a r c u r v a t u r e , to e l i m i n a t e t a n g e n t e r r o r . G r a d u a t i o n s a r e e x t e n d e d 15 m m . a t left for zero a d j u s t m e n t . A c o n t i n u o u s selection of b r i d g e v o l t a g e f r o m O t o 3 v o l t s i s p r o v i d e d , a n d t h e selection of o u t p u t v o l t a g e i s b y r o t a t i o n of a s i n g l e dial, t h i s d i a l r e a d i n g d i r e c t in m i l l i v o l t s p e r s p a n volt. C u r r e n t is c a l c u l a t e d s i m p l y b y m u l t i p l y i n g scale r e a d i n g by m u l t i p l i e r r e a d i n g b y sensitivity coefficieiatof g a l v a n o m e t e r . T o a d j u s t g a l v a n o m e t e r sensitivity a t e n p o s i t i o n A y r t o n g a l v a n o m e t e r s h u n t i s p r o v i d e d . G a l v a n o m e t e r sensitivity is a p p r o x i m a t e l y 0.006 m i c r o a m p e r e s m m . a n d g a l v a n o m e t e r s h u n t r a t i o s a r e f r o m 1:1 t o 1 0 0 0 : 1 . A t h r e e p o s i t i o n t o g g l e s w i t c h p e r m i t s that t h e sense of t h e g a l v a n o m e t e r scale r e m a i n u n c h a n g e d r e g a r d l e s s o f cell c u r r e n t d i r e c t i o n o r p o l a r i t y of t h e d r o p p i n g e l e c t r o d e . A t e n t u r n h e l i c a l p o t e n t i o m e t e r serves b o t h f o r u p s c a l e a n d d o w n s c a l e c o m p e n s a t i o n a n d for a d j u s t m e n t o f t h e g a l v a n o m e t e r zero p o s i t i o n . Another potentiometer incorporating a power switch serves t o select t h e d e s i r e d v o l t a g e a c r o s s t h e b r i d g e . A p a n e l m o u n t e d v o l t m e t e r a c c u r a t e t o 1.0% of full scale i n d i c a t e s the v o l t a g e e s t a b l i s h e d . T h e i n s t r u m e n t is m o u n t e d o n a cast a l u m i n u m base a n d enclosed i n a s h e e t m e t a l h o u s i n g p r o v i d e d w i t h a h i n g e d t o p a n d finished in b l a c k e n a m e l . A l l c o n t r o l s a r e m o u n t e d on a polished a l u m i n u m panel. S-29290 P O L A R O G R A P H — M a n u a l , Indicating, Model I I I , S a r g e n t . C o m p l e t e w i t h t h r e e dry cells, o n e g a l v a n o m e t e r l a m p , o n e set cell lead w i r e s , o n e c a l i b r a t i n g r e s i s t o r plug, 250,000 ohm, a n d cord a n d p l u g for connection t o s t a n d a r d o u t l e t s . Tor o p e r a t i o n from 115 volt 50 o r 6 0 cycle c i r c u i t s $390.00 SCIENTIFIC LABORATORY INSTRUMENTS • APPARATUS • SUPPLIES • CHEMICALS
E, H . SARGENT & C O M P A N Y , 4 - 6 4 7 W . FOSTER A V I . . - C H I C A G O 3 0 , I L L I N O I S M I C H I G A N D I V I S I O N , 1 9 5 9 EAST J E FFERSON STREET, DETROIT 7, M I C H I G A N S O U T H W E S T E R N D I V I S I O N , 5 9 1 5 PEELER STREET, D A L L A S 1 9 , T E X A S SOUTHEASTERN D I V I S I O N , 3 1 2 5 SEVENTH A V E . , N . , B I R M I N G H A M 4 , A L A . 2506
CHEMICAL
AND
ENGINEERING
NEWS
