POLAROGRAPH
MODEL I I I
Trademark Reg. U.S. Pat. Off.
MANUAL Ε. Η . 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 Chart Recording;
the Model
XII
Photographic Recording, and t h e M o d e l III M a n u a l . T h e Model III Polarograph m a y b e u s e d i n a n y p h a s e of p o l a r o g r a p h y , b u t i t is p a r t i c ularly r e c o m m e n d e d for appli c a t i o n s t o w h i c h i t is peculiarlysuited and in w h i c h recording facilities are unnecessary.
T h e 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 a n d w h e r e 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 form, characteristic of reversible r e a c t i o n s in v o l v i n g s i m p l e i o n s i n 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 . I n such cases, step h e i g h t m a y be m e a s u r e d as t h e differ ence b e t w e e n t w o p o i n t s , o n e o n 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 . F o r m e a s u r e m e n t s of this 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 as t h e M o d e l I I I is p r e f e r a b l e to a r e c o r d i n g P o l a r o g r a p h because of t h e speed a n d ease 'with w h i c h it m a y be o p e r a t e d even b y relatively 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 n o w in use for several d e t e r m i n a t i o n s , a M o d e l I I I m a y b e used for each 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 record i n g P o l a r o g r a p h for research p u r p o s e s a n d for establish i n g t h e c o n d i t i o n s of t h e r o u t i n e analyses. (3) I n t h e p e r f o r m a n c e of a m p e r o m e t r i c t i t r a t i o n s . (4) For 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 t h e 315 m m . l o n g , r e a d i l y visible scale a n d t h e sim plicity of design m a k e t h e M o d e l III 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 t h e basic circuit e m p l o y e d in P o l a r o g r a p h s . Essentially t h e M o d e l I I I p r o v i d e s facilities for t h e i n c r e m e n t a l a p p l i c a t i o n of v o l t a g e across t h e d r o p p i n g m e r c u r y e l e c t r o d e cell a n d for i n d i c a t i n g t h e r e s u l t a n t c u r r e n t 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 m e a s u r e d b y 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 l i n e 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, t o a t r a n s l u c e n t scale located a b o v e t h e i n s t r u m e n t p a n e l . T h e scale is d o u b l e g r a d u a t e d f r o m —150 t o + 1 5 0 m m .
SARGENT
w i t h zero center in r e d at t o p a n d from zero t o + 300 m m . in black at t h e b o t t o m . T h e scale is 31.5 cm. l o n g , w i t h circular 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 . at left for zero adjustment. A con t i n u o u s selection of b r i d g e v o l t a g e from 0 t o 3 volts is 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 is by rota tion of a single dial, this d i a l r e a d i n g direct in millivolts p e r s p a n volt. C u r r e n t is calculated s i m p l y by 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 by sensitivity coefficient of g a l v a n o m e t e r . T o adjust g a l v a n o m e t e r sen sitivity a ten 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 is 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 ratios a r e from 1:1 t o 1000:1. A t h r e e p o s i t i o n t o g g l e switch p e r m i t s t h a t 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 regardless of 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 electrode. A ten t u r n helical p o t e n t i o m e t e r serves b o t h for upscale 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 of t h e g a l v a n o m e t e r zero p o s i t i o n . A n o t h e r p o t e n t i o m e t e r i n c o r p o r a t i n g a p o w e r switch serves to select t h e desired v o l t a g e across 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 accurate to 1.0% of full scale indicates t h e v o l t a g e established. 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 alu-minum base a n d enclosed in a sheet 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 black e n a m e l . A l l c o n t r o l s a r e mounted 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 , Sargent. C o m p l e t e w i t h t h r e e d r y cells, o n e g a l v a n o m eter 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 resistor p l u g , 250,000 o h m , a n d c o r d a n d p l u g for c o n n e c t i o n t o s t a n d a r d outlets. For o p e r a t i o n from 115 volt 50 o r 6 0 cycle circuits $390.00
SCIENTIFIC LABORATORY INSTRUMENTS · APPARATUS · SUPPLIES · CHEMICALS
E. H. SARGENT & COMPANY, 4 6 4 7 W . FOSTER AVE., CHICAGO 3 0 ,
gataùx? Ή». fOO Hou*
/îvaiÎcittte
ILLINOIS
M I C H I G A N D I V I S I O N , 8560 WEST CHICAGO AVENUE, DETROIT 4, 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, DALLAS 1 9 , TEXAS SOUTHEASTERN D I V I S I O N , 3125 SEVENTH AVE., N., BIRMINGHAM 4 , ALA. Far further Information, circle number 27 A on Readers' Service Card, page 51 A
VOLUME
28, NO.
1, J A N U A R Y
1956
27 A
