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Notes on the preparation and construction of silver reductor columns
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SHORT COMMUNICATIONS
Procedure B When the amplifier is operated with increased gain, additional negative bias is required to set the recorder zero coincident with zero transmission. This additional voltage is obtained by changing connections at the photomultiplier voltage-supply regulator tubes so that minus 3oo V is supplied to the bias control and series regulator rather then --15o V. For convenience, a switch is installed so the operator can change from one voltage to the other. With the switch in the - - 3 0 0 V position, the steps in procedure A are followed. A pen excursion of about 289 times normal operation is obtained. The wiring diagram for the new circuit is shown in Fig. 2.
Albany Metallurgy Research Center, Bureau o/Mines, U.S. Department o/the Interior, Albany, Oreg. (U.S.A.)
EDWARD COGAN* HARRY FREUND* PETER ROMANS**
Received May 2ist, 196o * Analytical chemist, U.S. Department of the Interior, Bureau of Mines, Albany, Oreg. ** Physicist, U. S. Department of the Interior, Bureau of Mines, Albany, Oreg. Anal. Chim. dora, 23 (196o) 294-295
Notes on the preparation and construction of silver reductor columns* Silver for use in silver reductor columns is prepared b y a number of methods. The reductor originally described by WALDEN,HAMMETTAND EDMONDS5 used silver precipitated from an acidified silver nitrate solution by a copper sheet. Columns filled with this silver have a high reducing capacity but a very slow flow rate. The silver is very finely divided and packs down so tightly that liquid flow through the column is impeded; it is usually necessary to operate the column under reduced pressure. Silver prepared by reduction with sulfurous acid or formaldehyde is also finely divided and behaves similarly. Silver deposited electrolytically as low density "trees" was introduced by SMITH AND CAGLE4. It is now commercially available and is in common use. Electro-deposited silver forms a porous column and permits a rapid flow rate. Its major disadvantage is that it requires frequent regeneration. Although this is simply performed by treatment with dilute ammonia it would be advantageous to have a column which did not require frequent regeneration. A column combining the advantages of both types of silver and eliminating their disadvantages can be prepared by mixing the two types. By selection of various ratios of electro-deposited to copper-reduced silver, a column can be tailored to have various flow rates and capacities. For m a n y applications a I : I ratio (v/v) is satisfactory. The use of pulverized silver metal (2) and metal platelets (I) should provide still greater flexibility in the preparation of a column. In using a reductor column the operator must p a y close attention to the height of the liquid and not allow the liquid to drain below the level of the silver. If air enters * Publication authorized b y the Director, U.S. Geological Survey. Anal. Chim. Acla, 23 (196o) 295-296
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SHORT COMMUNICATIONS
the column, e n t r a p m e n t ensues, a n d the solution m a y channel a r o u n d m u c h of the silver. T h e danger of air e n t r a p m e n t can be overcome b y use of t h e column shown in Fig. I. The design is similar to t h a t of self-leveling ion-exchange columnsA. W i t h the d e l i v e r y t u b e opening a b o v e t h e level of the t o p of the silver bed, t h e liquid level will always
~!. Glass wool
Fig. I. Self-leveling reductor column. r e m a i n a b o v e the silver. A t a l l form funnel is used for the feed solution in order to t a k e a d v a n t a g e of t h e increased h y d r o s t a t i c h e a d of the liquid. T h e flow r a t e can be controlled b y a d j u s t m e n t of the stopcocks a n d the column can be used w i t h o u t a t t e n t i o n b y the operator. T h e column used in this l a b o r a t o r y was c o n s t r u c t e d from two I25-ml cylindrical s e p a r a t o r y funnels. To reduce b r e a k a g e the exit t u b e was f a b r i c a t e d from p o l y e t h y l e n e tubing. C o m m e r c i a l l y available self-leveling ion-exchange columns would be more convenient. U. S. Geological Survey, JOSEPH I. DINNIN Washington, D.C. (U.S.A.) 1 j . DOLEZAL, J. DRAHOI'~OVSK~" AND J. Z~KA, Collection Czech Chem. Communs., 24 (1959) 3649 . 2 H. •LASCHKA, Anal. Chim. Acta, 4 (195o) 242. 3 0 . SAMUELSON, [On Exchangers in Analytical Chemistry, John Wiley and Sons, New York, 1953, p. 80. 4 G. F. SMITH AND F. W. CAGLE, Anal. Chem., 2o (1948) I83. a G. H. WALDEN, L. P. HAMMETTAND S. M. EDMONDS,J. Am. Chem. Soc., 56 (1934) 35 ~ R e c e i v e d J u n e I 4 t h , 1960 Anal. Chim. Acta, 23 (196o) 295-296
SHORT COMMUNICATIONS
Procedure B When the amplifier is operated with increased gain, additional negative bias is required to set the recorder zero coincident with zero transmission. This additional voltage is obtained by changing connections at the photomultiplier voltage-supply regulator tubes so that minus 3oo V is supplied to the bias control and series regulator rather then --15o V. For convenience, a switch is installed so the operator can change from one voltage to the other. With the switch in the - - 3 0 0 V position, the steps in procedure A are followed. A pen excursion of about 289 times normal operation is obtained. The wiring diagram for the new circuit is shown in Fig. 2.
Albany Metallurgy Research Center, Bureau o/Mines, U.S. Department o/the Interior, Albany, Oreg. (U.S.A.)
EDWARD COGAN* HARRY FREUND* PETER ROMANS**
Received May 2ist, 196o * Analytical chemist, U.S. Department of the Interior, Bureau of Mines, Albany, Oreg. ** Physicist, U. S. Department of the Interior, Bureau of Mines, Albany, Oreg. Anal. Chim. dora, 23 (196o) 294-295
Notes on the preparation and construction of silver reductor columns* Silver for use in silver reductor columns is prepared b y a number of methods. The reductor originally described by WALDEN,HAMMETTAND EDMONDS5 used silver precipitated from an acidified silver nitrate solution by a copper sheet. Columns filled with this silver have a high reducing capacity but a very slow flow rate. The silver is very finely divided and packs down so tightly that liquid flow through the column is impeded; it is usually necessary to operate the column under reduced pressure. Silver prepared by reduction with sulfurous acid or formaldehyde is also finely divided and behaves similarly. Silver deposited electrolytically as low density "trees" was introduced by SMITH AND CAGLE4. It is now commercially available and is in common use. Electro-deposited silver forms a porous column and permits a rapid flow rate. Its major disadvantage is that it requires frequent regeneration. Although this is simply performed by treatment with dilute ammonia it would be advantageous to have a column which did not require frequent regeneration. A column combining the advantages of both types of silver and eliminating their disadvantages can be prepared by mixing the two types. By selection of various ratios of electro-deposited to copper-reduced silver, a column can be tailored to have various flow rates and capacities. For m a n y applications a I : I ratio (v/v) is satisfactory. The use of pulverized silver metal (2) and metal platelets (I) should provide still greater flexibility in the preparation of a column. In using a reductor column the operator must p a y close attention to the height of the liquid and not allow the liquid to drain below the level of the silver. If air enters * Publication authorized b y the Director, U.S. Geological Survey. Anal. Chim. Acla, 23 (196o) 295-296
296
SHORT COMMUNICATIONS
the column, e n t r a p m e n t ensues, a n d the solution m a y channel a r o u n d m u c h of the silver. T h e danger of air e n t r a p m e n t can be overcome b y use of t h e column shown in Fig. I. The design is similar to t h a t of self-leveling ion-exchange columnsA. W i t h the d e l i v e r y t u b e opening a b o v e t h e level of the t o p of the silver bed, t h e liquid level will always
~!. Glass wool
Fig. I. Self-leveling reductor column. r e m a i n a b o v e the silver. A t a l l form funnel is used for the feed solution in order to t a k e a d v a n t a g e of t h e increased h y d r o s t a t i c h e a d of the liquid. T h e flow r a t e can be controlled b y a d j u s t m e n t of the stopcocks a n d the column can be used w i t h o u t a t t e n t i o n b y the operator. T h e column used in this l a b o r a t o r y was c o n s t r u c t e d from two I25-ml cylindrical s e p a r a t o r y funnels. To reduce b r e a k a g e the exit t u b e was f a b r i c a t e d from p o l y e t h y l e n e tubing. C o m m e r c i a l l y available self-leveling ion-exchange columns would be more convenient. U. S. Geological Survey, JOSEPH I. DINNIN Washington, D.C. (U.S.A.) 1 j . DOLEZAL, J. DRAHOI'~OVSK~" AND J. Z~KA, Collection Czech Chem. Communs., 24 (1959) 3649 . 2 H. •LASCHKA, Anal. Chim. Acta, 4 (195o) 242. 3 0 . SAMUELSON, [On Exchangers in Analytical Chemistry, John Wiley and Sons, New York, 1953, p. 80. 4 G. F. SMITH AND F. W. CAGLE, Anal. Chem., 2o (1948) I83. a G. H. WALDEN, L. P. HAMMETTAND S. M. EDMONDS,J. Am. Chem. Soc., 56 (1934) 35 ~ R e c e i v e d J u n e I 4 t h , 1960 Anal. Chim. Acta, 23 (196o) 295-296