- Email: [email protected]
Portable analyzer for determination of dissolved oxygen in water.
A 10
Journal of Electroanalytical Chemistry
VOL. 1
photo-diodes has been developed for use .in chromatography, offering compactn e s s , r e l i a b i l i t y and v e r s a t i l i t y . When a light b e a m incident on the junction diode is i n t e r r u p t e d by a falling drop, a positive 4-volt pulse is produced o v e r the 1-Megohm load r e s i s t o r and t r i g g e r s the u n i v i b r a t o r c i r c u i t . A 500-ohm r e l a y with triple contacts is i n c o r p o r a t e d in the collector circuit. One contact o p e r a t e s the Sodeco counter, the second contact provides a negative 8.6 volt pulse for an output, w h e r e a s the third contact is conneoted to a second output. The use of a u n i v i b r a t o r between photo-diode and c o u n t e r e n s u r e s high stability in operation and p r e v e n t s the drop velocity being critical. In chromatography of radioactive ~pecies, the s e p a r a t i o n can be controlled by continuous m o n i t o r i n g of the effluent with a suitable detector coupled to a r a t e m e t e r and a r e c o r d e r . Ja. Inc. [281 REDOXOKINETIC TITRATION: A NEW ANALYTICAL TECHNIQUE. K . S . G . Doss, K. S u n d a r a r a j a n , U.K. N a r a y a n a n and S. Visvanathan. (Central E l e c t r o c h e m i c a l R e s e a r c h Institute, Karaikudi, South India.) E l e c t r o c h i m . A c t a , 1 (1959) 22. The method is based on that of Doss and A g a r v a l concerned with the sudden change of redoxokinetic potential at the e n d - p o i n t of an a n a l y t i c a l r e a c t i o n in a redox-system. The a p p a r a t u s c o n s i s t s of a stabilized a . c . s o u r c e , feeding through a r e s i s t ance, the p r i m a r y of a bell t r a n s f o r m e r ; with the aid of a p o t e n t i o m e t e r a c r o s s the s e c o n d a r y , any voltage between 0 and 6.5 V can be obtained. One of the t e r m i n a l s of the p o t e n t i o m e t e r is connected to a P t - m i c r o e l e e t r o d e , through a s e r i e s of three r e s i s t o r s ( r e s p e c t i v e l y 1, 10 and 40 K) which control the c u r r e n t - d e n s i t y to the r e q u i r e d value; the second t e r m i n a l is connected with the second m i c r o e l e c t r o d e . A third m i c r o e l e c t r o d e , earthed, is connected through an impedance (130H) and a g a l v a n o m e t e r to the second e l e c t r o d e ; all t h r e e e l e c t r o d e s a r e dipped into the solution to be titrated. The d . c . c u r r e n t m e a s u r e d by the g a l v a n o m e t e r shows sudden changes at the e n d - p o i n t ; p r e c i s i o n s of 0.4-0.02 % a r e obtained in the examples shown in the text. Ca. Cas. ,[29] DAS N F - D E K A M E T E R ALS GERAT ZUR DIELEKTRISCHEN W E R K S T O F F P R U FUNG. K. Slevogt und F. Oehme. Mitteilg. Inst. chem. - physikal. A n a l y s e n m e t h . , W e i l h e i m / O b b . , II/1959, 28-37. The close r e l a t i o n between c h e m i c a l a n d / o r physical s t r u c t u r e and the change of the d i e l e c t r i c constant (D. C.) or the d i e l e c t r i c loss (D. L. ) with frequency and t e m p e r a t u r e opens new ways to the n o n - d e s t r u c t i v e testing of m a t e r i a l s . F o r such p u r p o s e s the " N F - D e k a m e t e r DK 05" (manufactured by WTW, W e i l h e i m / O b b . ) p e r m i t s m e a s u r e m e n t s in a f r e q u e n c y - r a n g e from 40 c / s to 100 k c / s . It is a modified Schering bridge with a c a t h o d e - r a y tube as tuning indicator. By m e a n s of the shape of the s o - c a l l e d p h a s e - e l l i p s e the b a l a n c i n g of the bridge is very easy to perform. On the b a s i s o f D e b y e ' s r e l a x a t i o n f o r m u l a a n u m b e r of applications a r e d i s cussed. Special c o n s i d e r a t i o n is given to f r e e z i n g phenomena of p l a s t i c i s e d highpolymers~ the oxidative d e t e r i o r a t i o n of l u b r i c a n t s , the influence of the degree of c h l o r i n a t i o n of h y d r o c a r b o n s and the composition of m i x t u r e s of oil and r e s i n s , all with r e s p e c t to the change of d i e l e c t r i c p r o p e r t i e s . F r . Oe. [301 PORTABLE ANALYZER FOR DETERMINATION OI: DISSOLVED OXYGEN IN WATER. C . P . T y l e r and J . H . K a r c h m e r . (Humble Oil & Refining Co., Baytown, T e x . , U. S . A . ) Anal. C h e m . , 31 (1959) 499. An i n s t r u m e n t is d e s c r i b e d which e l i m i n a t e s the known difficulties in d e t e r m i n i n g dissolved oxygen with a portable polarograph. A very s h o r t Hg drop time
1960
A b s t r a c t s Section
A 11
of about 0.25 sec produces a c u r r e n t r e l a t i v e l y i n s e n s i t i v e to agitation o r sample flow. The c a p i l l a r y is mounted h o r i z o n t a l l y in the cell. The method is applicable to w a t e r s a m p l e s in the p H - r a n g e between 0.001 M and 0.05 M. The addition of a s m a l l quantity of a r e a g e n t containing gelatin, phenol and sodium chloride allows m e a s u r e m e n t outside the indicated range. A Weston Model 741 m i c r o a m p e r e m e t e r is used. Detailed i n s t r u c t i o n s for p r o c e d u r e , a s s e m b l y of the a p p a r a t u s , and s e l e c t i o n of the c a p i l l a r y a r e given. KI. Gr. [31] ELECTRONIC C O N T R O L L E D - POTENTIAL COULOMETRIC TITRATOR. M . T . Kelley, H.C. Jones and D. J. F i s h e r . (Anal. Chem. D i v . , Oak Ridge National L a b . , Oak Ridge, T e n n . , U . S . A . ) Anal. C h e m . , 31 (1959) 488. A n a l t e r n a t i n g c u r r e n t line operated i n s t r u m e n t for c o u l o m e t r i c t i t r a t i o n s at a controlled potential is d e s c r i b e d . The potential of only the working electrode is controlled by a s t a b i l i z e d difference a m p l i f i e r combined with a t r a n s i s t o r c u r r e n t a m p l i f i e r . The e l e c t r o l y s i s c u r r e n t is i n t e g r a t e d and the i n t e g r a l is read as a voltage. The i n s t r u m e n t can be used for m a n u a l o r automatic t i t r a t i o n s . The cell has three e l e c t r o d e s : the w o r k i n g electrode (Pt), a r e f e r e n c e electrode of constant potential and a Hg pool electrode as controlled cathode for reduction or a P t - g a u z e anode for oxidation. Under reduction operation the pool solution interface i s s t i r red by a s t i r r e r with constant speed to obtain a high i n i t i a l c u r r e n t . C o n s t r u c t i o n d e t a i l s and w i r i n g d i a g r a m a r e given. K1. Gr. [32] TRANSISTORIZED SWITCH FOR DERIVATIVE POLAROGRAPHY. J . K r u g e r s , (Lab. for Anal. C h e m . , U n i v e r s i t y of A m s t e r d a m , the N e t h e r l a n d s . ) Anal. C h e m . , 31 (1959) 444. An e l e c t r o n i c switch s y s t e m is d e s c r i b e d to r e p l a c e the m e c i m n i e a l switching s y s t e m used by Ishibashi and Fujiuaga in d e r i v a t i v e polarography. With the s y s tem d e s c r i b e d in this p a p e r a s m a l l d i r e c t c u r r e n t can be converted into an a l t e r nating c u r r e n t of any d e s i r e d frequency between 0.i c / s and 10 k e / s . W i r i n g d i a g r a m and technical data a r e given. The influence of frequency on i - E c u r v e s is shown with a solution of Cd chloride. The m o s t suitable frequency of the s u p e r imposed a l t e r n a t i n g c u r r e n t is about 20 c/s. The peak height depends on frequency. It is f a i r l y constant for Cd solutions between 30 - 70 c / s . F o r Zn it holds true between 30 - 70 c / s . Even a square wave can be produced with the g e n e r a t o r des c r i b e d . The influence of the s y m m e t r y grade on the curve of Cd chloride solutions is d e m o n s t r a t e d . If the s q u a r e wave is very a s y m m e t r i c and the frequency about 500 c / s the i - E curve b e c o m e s s i m i l a r to that in c l a s s i c polarography. K1. Gr. SEE ALSO: [ 8 , 3 3 , 3 6 , 38, 39, 63, 64, 66,89,95, 96,108,111].
3. P O L A R O G R A P H Y
[33] THE USE OF THE POOL CATHODE IN POLAROGRAPHY. R . C . R o o n e y . (Brit. C a s t Iron R e s e a r c h A s s . , B i r m i n g h a m , G r e a t B r i t a i n . ) T a l a n t a , 2 (1959) 190. P o l a r o g r a p h y using a m e r c u r y poo ! cathode has been d e s c r i b e d previot~sly Anal. Chem., 25 (1953) 1691; 26 (1954) 963, 27 (1955) 1360) and i n c r e a s e d s e n s i t i v i t y over the dropping m e r c u r y electrode has been c l a i m e d for conventional polaro-
Journal of Electroanalytical Chemistry
VOL. 1
photo-diodes has been developed for use .in chromatography, offering compactn e s s , r e l i a b i l i t y and v e r s a t i l i t y . When a light b e a m incident on the junction diode is i n t e r r u p t e d by a falling drop, a positive 4-volt pulse is produced o v e r the 1-Megohm load r e s i s t o r and t r i g g e r s the u n i v i b r a t o r c i r c u i t . A 500-ohm r e l a y with triple contacts is i n c o r p o r a t e d in the collector circuit. One contact o p e r a t e s the Sodeco counter, the second contact provides a negative 8.6 volt pulse for an output, w h e r e a s the third contact is conneoted to a second output. The use of a u n i v i b r a t o r between photo-diode and c o u n t e r e n s u r e s high stability in operation and p r e v e n t s the drop velocity being critical. In chromatography of radioactive ~pecies, the s e p a r a t i o n can be controlled by continuous m o n i t o r i n g of the effluent with a suitable detector coupled to a r a t e m e t e r and a r e c o r d e r . Ja. Inc. [281 REDOXOKINETIC TITRATION: A NEW ANALYTICAL TECHNIQUE. K . S . G . Doss, K. S u n d a r a r a j a n , U.K. N a r a y a n a n and S. Visvanathan. (Central E l e c t r o c h e m i c a l R e s e a r c h Institute, Karaikudi, South India.) E l e c t r o c h i m . A c t a , 1 (1959) 22. The method is based on that of Doss and A g a r v a l concerned with the sudden change of redoxokinetic potential at the e n d - p o i n t of an a n a l y t i c a l r e a c t i o n in a redox-system. The a p p a r a t u s c o n s i s t s of a stabilized a . c . s o u r c e , feeding through a r e s i s t ance, the p r i m a r y of a bell t r a n s f o r m e r ; with the aid of a p o t e n t i o m e t e r a c r o s s the s e c o n d a r y , any voltage between 0 and 6.5 V can be obtained. One of the t e r m i n a l s of the p o t e n t i o m e t e r is connected to a P t - m i c r o e l e e t r o d e , through a s e r i e s of three r e s i s t o r s ( r e s p e c t i v e l y 1, 10 and 40 K) which control the c u r r e n t - d e n s i t y to the r e q u i r e d value; the second t e r m i n a l is connected with the second m i c r o e l e c t r o d e . A third m i c r o e l e c t r o d e , earthed, is connected through an impedance (130H) and a g a l v a n o m e t e r to the second e l e c t r o d e ; all t h r e e e l e c t r o d e s a r e dipped into the solution to be titrated. The d . c . c u r r e n t m e a s u r e d by the g a l v a n o m e t e r shows sudden changes at the e n d - p o i n t ; p r e c i s i o n s of 0.4-0.02 % a r e obtained in the examples shown in the text. Ca. Cas. ,[29] DAS N F - D E K A M E T E R ALS GERAT ZUR DIELEKTRISCHEN W E R K S T O F F P R U FUNG. K. Slevogt und F. Oehme. Mitteilg. Inst. chem. - physikal. A n a l y s e n m e t h . , W e i l h e i m / O b b . , II/1959, 28-37. The close r e l a t i o n between c h e m i c a l a n d / o r physical s t r u c t u r e and the change of the d i e l e c t r i c constant (D. C.) or the d i e l e c t r i c loss (D. L. ) with frequency and t e m p e r a t u r e opens new ways to the n o n - d e s t r u c t i v e testing of m a t e r i a l s . F o r such p u r p o s e s the " N F - D e k a m e t e r DK 05" (manufactured by WTW, W e i l h e i m / O b b . ) p e r m i t s m e a s u r e m e n t s in a f r e q u e n c y - r a n g e from 40 c / s to 100 k c / s . It is a modified Schering bridge with a c a t h o d e - r a y tube as tuning indicator. By m e a n s of the shape of the s o - c a l l e d p h a s e - e l l i p s e the b a l a n c i n g of the bridge is very easy to perform. On the b a s i s o f D e b y e ' s r e l a x a t i o n f o r m u l a a n u m b e r of applications a r e d i s cussed. Special c o n s i d e r a t i o n is given to f r e e z i n g phenomena of p l a s t i c i s e d highpolymers~ the oxidative d e t e r i o r a t i o n of l u b r i c a n t s , the influence of the degree of c h l o r i n a t i o n of h y d r o c a r b o n s and the composition of m i x t u r e s of oil and r e s i n s , all with r e s p e c t to the change of d i e l e c t r i c p r o p e r t i e s . F r . Oe. [301 PORTABLE ANALYZER FOR DETERMINATION OI: DISSOLVED OXYGEN IN WATER. C . P . T y l e r and J . H . K a r c h m e r . (Humble Oil & Refining Co., Baytown, T e x . , U. S . A . ) Anal. C h e m . , 31 (1959) 499. An i n s t r u m e n t is d e s c r i b e d which e l i m i n a t e s the known difficulties in d e t e r m i n i n g dissolved oxygen with a portable polarograph. A very s h o r t Hg drop time
1960
A b s t r a c t s Section
A 11
of about 0.25 sec produces a c u r r e n t r e l a t i v e l y i n s e n s i t i v e to agitation o r sample flow. The c a p i l l a r y is mounted h o r i z o n t a l l y in the cell. The method is applicable to w a t e r s a m p l e s in the p H - r a n g e between 0.001 M and 0.05 M. The addition of a s m a l l quantity of a r e a g e n t containing gelatin, phenol and sodium chloride allows m e a s u r e m e n t outside the indicated range. A Weston Model 741 m i c r o a m p e r e m e t e r is used. Detailed i n s t r u c t i o n s for p r o c e d u r e , a s s e m b l y of the a p p a r a t u s , and s e l e c t i o n of the c a p i l l a r y a r e given. KI. Gr. [31] ELECTRONIC C O N T R O L L E D - POTENTIAL COULOMETRIC TITRATOR. M . T . Kelley, H.C. Jones and D. J. F i s h e r . (Anal. Chem. D i v . , Oak Ridge National L a b . , Oak Ridge, T e n n . , U . S . A . ) Anal. C h e m . , 31 (1959) 488. A n a l t e r n a t i n g c u r r e n t line operated i n s t r u m e n t for c o u l o m e t r i c t i t r a t i o n s at a controlled potential is d e s c r i b e d . The potential of only the working electrode is controlled by a s t a b i l i z e d difference a m p l i f i e r combined with a t r a n s i s t o r c u r r e n t a m p l i f i e r . The e l e c t r o l y s i s c u r r e n t is i n t e g r a t e d and the i n t e g r a l is read as a voltage. The i n s t r u m e n t can be used for m a n u a l o r automatic t i t r a t i o n s . The cell has three e l e c t r o d e s : the w o r k i n g electrode (Pt), a r e f e r e n c e electrode of constant potential and a Hg pool electrode as controlled cathode for reduction or a P t - g a u z e anode for oxidation. Under reduction operation the pool solution interface i s s t i r red by a s t i r r e r with constant speed to obtain a high i n i t i a l c u r r e n t . C o n s t r u c t i o n d e t a i l s and w i r i n g d i a g r a m a r e given. K1. Gr. [32] TRANSISTORIZED SWITCH FOR DERIVATIVE POLAROGRAPHY. J . K r u g e r s , (Lab. for Anal. C h e m . , U n i v e r s i t y of A m s t e r d a m , the N e t h e r l a n d s . ) Anal. C h e m . , 31 (1959) 444. An e l e c t r o n i c switch s y s t e m is d e s c r i b e d to r e p l a c e the m e c i m n i e a l switching s y s t e m used by Ishibashi and Fujiuaga in d e r i v a t i v e polarography. With the s y s tem d e s c r i b e d in this p a p e r a s m a l l d i r e c t c u r r e n t can be converted into an a l t e r nating c u r r e n t of any d e s i r e d frequency between 0.i c / s and 10 k e / s . W i r i n g d i a g r a m and technical data a r e given. The influence of frequency on i - E c u r v e s is shown with a solution of Cd chloride. The m o s t suitable frequency of the s u p e r imposed a l t e r n a t i n g c u r r e n t is about 20 c/s. The peak height depends on frequency. It is f a i r l y constant for Cd solutions between 30 - 70 c / s . F o r Zn it holds true between 30 - 70 c / s . Even a square wave can be produced with the g e n e r a t o r des c r i b e d . The influence of the s y m m e t r y grade on the curve of Cd chloride solutions is d e m o n s t r a t e d . If the s q u a r e wave is very a s y m m e t r i c and the frequency about 500 c / s the i - E curve b e c o m e s s i m i l a r to that in c l a s s i c polarography. K1. Gr. SEE ALSO: [ 8 , 3 3 , 3 6 , 38, 39, 63, 64, 66,89,95, 96,108,111].
3. P O L A R O G R A P H Y
[33] THE USE OF THE POOL CATHODE IN POLAROGRAPHY. R . C . R o o n e y . (Brit. C a s t Iron R e s e a r c h A s s . , B i r m i n g h a m , G r e a t B r i t a i n . ) T a l a n t a , 2 (1959) 190. P o l a r o g r a p h y using a m e r c u r y poo ! cathode has been d e s c r i b e d previot~sly Anal. Chem., 25 (1953) 1691; 26 (1954) 963, 27 (1955) 1360) and i n c r e a s e d s e n s i t i v i t y over the dropping m e r c u r y electrode has been c l a i m e d for conventional polaro-