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High frequency titrations. I. The silver-thiocyanate reaction
A 24
Journal of Electroanalytical Chemistry
VOL. 1
5. CONDUCTOMETRY
[73]
DETERMINATION OF FLUORIDE BY CONDUCTOMETRIC TITRATION. H. Kubota and J. G. Surak. (Anal. Chem. Div., Oak Ridge National L a b o r a t o r y , Term., U. S. A. ) Anal. C h e m . , 31 (1959) 283. Conduetometrie ~titration of fluoride with lanthanum acetate gives r e s u l t s whose r e p r o d u c i b i l i t y and a c c u r a c y is b e t t e r than those of other known methods for det e r m i n i n g fluoride. The method d e s c r i b e d is b e s t applied to the t i t r a t i o n of d i s t i l lates of the W i l l a r d - W i n t e r s e p a r a t i o n . A modified s e m i - m i c r o d i s t i l l a t i o n appar a t u s is used. The c o n d u c t o m e t r i c a l l y indicated r e a c t i o n is H2SiF s + 2La(OAe)3 + 2 H20 -- 6 HOAc + SiO2 + 2LaF 3. Standard deviations are below 1%. A S e r f a s s conductivity bridge with a magic eye indicator is used in this investigation. The break is s h a r p and reproducible. K1. Gr. [74] _HIGH FREQUENCY TITRATIONS. II. THE MERCURY (II)-THIOCYANATE REACTION. A . K . Mukheii and B.R. Sant. (Coates Chem. L a b . , Louisiana State Univ e r s i t y , U . S . A . ) Anal. C h i m . A c t a , 20 (1959)259. In a previous c o m m u n i c a t i o n , it has been shown that the high frequency (oscillometrie) technique can be suitably employed for the end-point detection in a p r e cipitation r e a c t i o n between Ag+ and SCN-. Because Hg (II) thiocyanate is s l i g h t l y d i s s o c i a t e d , it was thought i n t e r e s t i n g to study this r e a c t i o n with the s a m e t e c h nique. The t i t r a t i o n of Hg (II) n i t r a t e with thiocyanate gives one inflection c o r r e -~ sponding to the formation of HgISCN)2 , while in the r e v e r s e t i t r a t i o n the f o r m a U o n o f Hg(SCN)+ is also indicated. The method is useful for a rapid d e t e r m i n a t i o n of very s m a l l quantities of Hg o r thiocyanate in highly dilute solutions. The t i t r a Uons can be effected in the p r e s e n c e of n i t r i c acid provided its total acidity in the s y s t e m does not exceed about 1/300 N. P. Mae. [751 .HIGH FREQUENCY TITRATIONS. I. THE SILVER-THIOCYANATE R E A C T I O N . B . R . Sant and A . K . Mukheii. (Coates Chem. L a b . , Louisiana State U n i v e r s i t y , U . S . A . ) Anal. C h i m . A c t a , 20 (1959) 124. The chief advantage of the p r o c e d u r e s used in high frequency t i t r a t i o n s is the
isolation of the s y s t e m from e l e c t r o d e s and other active p a r t s of the i n s t r u m e n t without i m p a i r i n g t h e i r r e s p o n s e to slight changes in the composition of the s y s tem. The purpose of the p r e s e n t work was to investigate with the aid of these techniques r e a c t i o n s involving the p r e c i p i t a t i o n o r soluble complex f o r m a t i o n of simple and c o m p l e x metal thiocyanates, and to a s s e s s the a c c u r a c y of the method for a n a l y s i s of m g quantities of m a t e r i a l in highly dilute solutions. It was possible to t i t r a t e s m a l l amounts of Ag at dilutions down to 1/4000 M with a m m o n i u m o r potassium thioeyanate. R e v e r s e t i t r a t i o n s of the s a m e o r d e r of dilution are a l s o feasible. P. Mae.
[76] .DETERMINATION OF THALLIUM BY HIGH-FREQUENCY TITRATION WITH SODIUM TETRAPHENYLBORON. A . R . Veis and A. F. Yevinsh. (Latvian State Unive r s i t y , Riga, U . S . S . R . ) Z. anal. e h i m . , 14 (1959) 143. 5 to 20 rag T1 can be t i t r a t e d with the use of the h i g h - f r e q u e n c y technique and with 0.2 M sodium t e t r a p h e n y l b o r o n as v o l u m e t r i c reagent. The p r e s e n c e of C I ' , SO42-, NO3, CO 2-, CH3COO- , Na+, Zn 2+, Cd 2+ and Cu2+ cause no i n t e r f e r e n c e . The modified apparatus d e s c r i b e d by G. G. Blake ( A u s t r a l i a n J. S c i . , 10 ~1947) 80) was used. Ja. Zy.
Journal of Electroanalytical Chemistry
VOL. 1
5. CONDUCTOMETRY
[73]
DETERMINATION OF FLUORIDE BY CONDUCTOMETRIC TITRATION. H. Kubota and J. G. Surak. (Anal. Chem. Div., Oak Ridge National L a b o r a t o r y , Term., U. S. A. ) Anal. C h e m . , 31 (1959) 283. Conduetometrie ~titration of fluoride with lanthanum acetate gives r e s u l t s whose r e p r o d u c i b i l i t y and a c c u r a c y is b e t t e r than those of other known methods for det e r m i n i n g fluoride. The method d e s c r i b e d is b e s t applied to the t i t r a t i o n of d i s t i l lates of the W i l l a r d - W i n t e r s e p a r a t i o n . A modified s e m i - m i c r o d i s t i l l a t i o n appar a t u s is used. The c o n d u c t o m e t r i c a l l y indicated r e a c t i o n is H2SiF s + 2La(OAe)3 + 2 H20 -- 6 HOAc + SiO2 + 2LaF 3. Standard deviations are below 1%. A S e r f a s s conductivity bridge with a magic eye indicator is used in this investigation. The break is s h a r p and reproducible. K1. Gr. [74] _HIGH FREQUENCY TITRATIONS. II. THE MERCURY (II)-THIOCYANATE REACTION. A . K . Mukheii and B.R. Sant. (Coates Chem. L a b . , Louisiana State Univ e r s i t y , U . S . A . ) Anal. C h i m . A c t a , 20 (1959)259. In a previous c o m m u n i c a t i o n , it has been shown that the high frequency (oscillometrie) technique can be suitably employed for the end-point detection in a p r e cipitation r e a c t i o n between Ag+ and SCN-. Because Hg (II) thiocyanate is s l i g h t l y d i s s o c i a t e d , it was thought i n t e r e s t i n g to study this r e a c t i o n with the s a m e t e c h nique. The t i t r a t i o n of Hg (II) n i t r a t e with thiocyanate gives one inflection c o r r e -~ sponding to the formation of HgISCN)2 , while in the r e v e r s e t i t r a t i o n the f o r m a U o n o f Hg(SCN)+ is also indicated. The method is useful for a rapid d e t e r m i n a t i o n of very s m a l l quantities of Hg o r thiocyanate in highly dilute solutions. The t i t r a Uons can be effected in the p r e s e n c e of n i t r i c acid provided its total acidity in the s y s t e m does not exceed about 1/300 N. P. Mae. [751 .HIGH FREQUENCY TITRATIONS. I. THE SILVER-THIOCYANATE R E A C T I O N . B . R . Sant and A . K . Mukheii. (Coates Chem. L a b . , Louisiana State U n i v e r s i t y , U . S . A . ) Anal. C h i m . A c t a , 20 (1959) 124. The chief advantage of the p r o c e d u r e s used in high frequency t i t r a t i o n s is the
isolation of the s y s t e m from e l e c t r o d e s and other active p a r t s of the i n s t r u m e n t without i m p a i r i n g t h e i r r e s p o n s e to slight changes in the composition of the s y s tem. The purpose of the p r e s e n t work was to investigate with the aid of these techniques r e a c t i o n s involving the p r e c i p i t a t i o n o r soluble complex f o r m a t i o n of simple and c o m p l e x metal thiocyanates, and to a s s e s s the a c c u r a c y of the method for a n a l y s i s of m g quantities of m a t e r i a l in highly dilute solutions. It was possible to t i t r a t e s m a l l amounts of Ag at dilutions down to 1/4000 M with a m m o n i u m o r potassium thioeyanate. R e v e r s e t i t r a t i o n s of the s a m e o r d e r of dilution are a l s o feasible. P. Mae.
[76] .DETERMINATION OF THALLIUM BY HIGH-FREQUENCY TITRATION WITH SODIUM TETRAPHENYLBORON. A . R . Veis and A. F. Yevinsh. (Latvian State Unive r s i t y , Riga, U . S . S . R . ) Z. anal. e h i m . , 14 (1959) 143. 5 to 20 rag T1 can be t i t r a t e d with the use of the h i g h - f r e q u e n c y technique and with 0.2 M sodium t e t r a p h e n y l b o r o n as v o l u m e t r i c reagent. The p r e s e n c e of C I ' , SO42-, NO3, CO 2-, CH3COO- , Na+, Zn 2+, Cd 2+ and Cu2+ cause no i n t e r f e r e n c e . The modified apparatus d e s c r i b e d by G. G. Blake ( A u s t r a l i a n J. S c i . , 10 ~1947) 80) was used. Ja. Zy.